Iron, an essential micronutrient for biological processes (Forbes, 2009), serves critical functions across various metabolic pathways, such as facilitating oxygen transportation, supporting energy metabolism, aiding nucleotide synthesis, and participating in electron transport. Iron homeostasis, which is critical for fundamental physiological processes, is regulated and maintained by iron metabolism (Hentze et al., 2010; Prá et al., 2012). Maintaining iron levels within a balanced range is crucial, as excessive amounts can lead to toxicity (Hentze et al., 2010). Imbalances in the molecular processes governing iron absorption, utilization, storage, and elimination contribute to disease development (Muñoz et al., 2011a; Muñoz et al., 2011b; Theil, 2000). Excessive iron accumulation, coupled with its propensity to generate reactive oxygen species (ROS), suggests its potential involvement in various chronic illnesses, including diabetes, neurological disorders, cardiomyopathy, and several human cancers, such as lung cancer, colorectal cancer, and breast cancer (Jiang et al., 2004; Menshawey et al., 2020; Sempos et al., 1994; Stevens et al., 1988; Ward and Cloonan, 2019). Iron-induced oxidative stress may damage DNA, proteins, and organelles by producing harmful radicals and hydrogen peroxide via Haber–Weiss and Fenton-type reactions (Eaton and Qian, 2002; Nelson, 1992; Toyokuni, 1996). Furthermore, the role of iron in cell proliferation implies its importance in the expansion of malignant cells and may confer a selective advantage for tumor growth (Marques et al., 2014). In breast cancer cases, dysregulation of iron-binding proteins, such as transferrin, which facilitates the delivery of ferric ions into cells, and iron-transporting proteins, like ferroportin, which is responsible for exporting iron out of cells, is frequently observed. One observed phenomenon involves the downregulation of ferroportin levels by hepcidin through posttranscriptional modifications. This results in a greater ratio of hepcidin to ferroportin, ultimately leading to increased ferritin expression and subsequent iron overload (Pinnix et al., 2010; Zhang et al., 2014). Moreover, alterations in transferrin levels have also been noted (Chang et al., 2019; Rufaida Mustafa Ahmed and Nazik Elmalaika Obaid Seid Ahmed, 2017). Iron overload significantly increases the vulnerability of postmenopausal women to breast cancer development by stimulating and fostering oxidative stress (Huang, 2008; Jian et al., 2011). Moreover, recent research has indicated that elevated iron levels within the inflammatory microenvironment of breast tissue may contribute to the progression and metastasis of breast cancer (Cheng et al., 2020). Increased estrogen levels in breast tissue disturb intracellular iron metabolism, leading to excess iron. This excess iron can trigger the generation of superoxide anions and convert ferritin-bound Fe³⁺ to Fe²⁺, inducing estrogen-induced oxidative stress on nucleic acids and subsequent breast carcinogenesis (Islam et al., 2022). Therefore, directing interventions toward iron metabolic pathways and modulating cellular iron homeostasis could present a promising avenue for breast cancer treatment, by utilizing strategies such as iron chelation and addressing iron overload.

The excess cellular iron reacts with hydrogen peroxide (H₂O₂) in the Fenton reaction, producing harmful hydroxyl radicals. These radicals damage lipids, proteins, and DNA, potentially leading to ferroptosis. Ferroptosis, dependent on iron, involves phospholipid peroxidation resulting from disrupted cellular iron homeostasis and redox balance (Dixon et al., 2012; Jiang X et al., 2021). Recently, researchers have delved deeply into the mechanisms of ferroptosis, concentrating on three main areas: iron metabolism and ROS production, lipid metabolism, and the system Xc-GSH-GPX4 pathway (Hassannia et al., 2019; Jiang X et al., 2021). Elevated iron accumulation is necessary to initiate ferroptosis, and alterations in genes and proteins involved in iron metabolism can modulate ferroptosis sensitivity by modifying cellular iron levels (Jiang X et al., 2021). Transferrin (TF) binds to Fe³⁺ with high affinity in the bloodstream. Once bound to TF, Fe³⁺ is transported into cells via transferrin receptor 1 (TFR1). Inside endosomes, STEAP3 reduces Fe³⁺ to Fe²⁺, which is then transported into the labile iron pool by divalent metal transporter 1 (DMT1). Once in the labile iron pool, Fe²⁺ contributes to the production of ROS and facilitates lipoxygenase activation. Excess iron is stored in ferritin, which undergoes autophagy-mediated degradation, a process defined as ferritinophagy, releasing labile Fe²⁺ and promoting lipid peroxidation (Fang et al., 2023; Jiang X et al., 2021; Paul et al., 2017; Zheng and Conrad, 2020). Furthermore, ROS production is augmented by mitochondrial metabolism (Jiang X et al., 2021; Stockwell, 2022). Importantly, cellular iron import or export is critical for regulating ferroptosis. Transferrin and its receptor (TFR1) enable iron transport into cells, thus initiating ferroptosis (Figure 1) (Wang et al., 2023b). The modulation of ferroptosis involves regulating the expression of TFR1, illustrating its capacity to either promote or inhibit the process. Ferritin heavy chain 1 (FTH1) modulates iron storage by interacting with NCOA4, which initiates iron autophagy. This process releases iron, triggering mitochondrial lipid peroxidation and subsequent ferroptosis (Fang et al., 2021). Research indicates that knocking out NCOA4 diminishes iron autophagy, making cells more resistant to ferroptosis (Fang et al., 2021). Moreover, ferroportin (FPN), an essential iron exporter for maintaining iron balance (Yang et al., 2020), has been identified as a potential target for preventing ferroptosis through the regulation of FPN protein degradation (Traeger et al., 2022; Yang et al., 2020). Hence, modulating cellular sensitivity to ferroptosis through regulating iron metabolism has emerged as an effective strategy for treating ferroptosis-related diseases (Jiang X et al., 2021). Clinically, iron chelators are employed to eliminate excess iron from the body, representing a viable treatment option for managing diseases associated with ferroptosis (Feng W. et al., 2022). Polyunsaturated fatty acid phospholipids (PUFA-PLs) act as key substrates for lipid peroxidation (LPO) (Feng W. et al., 2022), and the biosynthetic pathway of PUFA-PLs is crucial in regulating the initiation of ferroptosis (Feng W. et al., 2022; Li and Li, 2020). Lipid metabolism, one of the three core metabolic pathways, is critical in the development of cardiovascular disease, obesity, cancer, and other conditions (Bacci et al., 2021). As a result, enzymes regulating lipid synthesis, breakdown, and β-oxidation have become prominent therapeutic targets (Zechner et al., 2012). Abnormalities in lipid metabolism, particularly in fatty acid metabolism, are now widely acknowledged as key drivers in the pathogenesis of ferroptosis (Li and Li, 2020; Liang et al., 2022). Monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs) exert opposing effects on ferroptosis, likely due to their differences in chemical structure and oxidative stability, which influence their susceptibility to lipid peroxidation and thereby modulate ferroptosis (Li and Li, 2020; Magtanong et al., 2019). The balance between MUFA-PLs and PUFA-PLs, derived from monounsaturated and polyunsaturated fatty acids, respectively, is critical in modulating cellular sensitivity to ferroptosis (Li and Li, 2020; Magtanong et al., 2019). In this process, acetyl-CoA is first converted to malonyl-CoA via acetyl-CoA carboxylase (ACC), leading to the production of PUFAs. Long-chain acyl-CoA synthetase 4 (ACSL4) and lysophosphatidylcholine acyltransferase 3 (LPCAT3) (Stockwell, 2022) then facilitate the incorporation of PUFAs into phospholipids (PUFA-PLs) (Stockwell, 2022). Under the action of iron-dependent lipoxygenases and reactive oxygen species (ROS), PUFA-PLs are oxidized into PUFA-PL-OOH, triggering the onset of ferroptosis (Li and Li, 2020; Magtanong et al., 2019). Furthermore, the enzymatic activities of ACSL3 and ACSL4 play a critical role in modulating cellular sensitivity to ferroptosis (Figure 1) (Li and Li, 2020; Magtanong et al., 2019). Interestingly, ACSL3 activation has been found to protect cells from ferroptosis, with studies highlighting its role in gastric and breast cancer cells (Ma et al., 2022; Xie et al., 2022).

Copper, a crucial trace transition metal, is essential for enzymes and proteins in diverse organisms and influences biological processes like mitochondrial function, respiration, antioxidant defense, and cell proliferation. It exists primarily in two oxidation states, Cu⁺ and Cu²⁺, impacting its bioactivity (Ying et al., 2023). Cellular copper homeostasis is tightly regulated by copper-dependent proteins such as copper transporter 1 (CTR1) for uptake, copper chaperones for transport, and copper-transporting P-type ATPases (copper ATPases) for export, ensuring that optimal intracellular copper levels are crucial for overall health. Disruptions in copper homeostasis have been observed in various cancers like colorectal, lung, and breast cancer (Chen L. et al., 2022; Denoyer et al., 2015; Jiang Z et al., 2023). Copper holds significant importance in tumorigenesis and cancer progression, as it can bind and activate key molecules within multiple signaling pathways present in cancer, including breast cancer cells. Within these pathways, the Wnt signaling pathway is vital for maintaining breast cancer stem cells (BCSCs) stemness. Recent studies have suggested that disulfiram/copper (DSF/Cu) complexes can hinder cancer cell proliferation and metastasis by reducing the expression of β-catenin and C-myc, which are critical components of the Wnt pathway (Shivnani et al., 2023; Wang et al., 2020). In addition, the Notch pathway is essential for multiple biological processes in breast cancer cells, encompassing cell differentiation, apoptosis, and cell cycle progression (Farnie and Clarke, 2007). In essence, copper influences breast cancer metastasis through the promotion of Notch ligand shedding and the activation of key signaling pathways, such as the RAS-RAF-MEK-ERK and receptor tyrosine kinase (RTK)-related pathways, ultimately facilitating cancer cell migration and proliferation (Grasso et al., 2021). Furthermore, several studies have shown elevated copper levels in tumor tissues and serum across different cancer types, including breast, gastric, and lung cancers. In breast cancer patients, high serum copper levels are correlated with advanced tumor stage and disease progression (Guo et al., 2021; Heuberger et al., 2022; Jin et al., 2022; Pavithra et al., 2015). These findings underscore the significant regulatory role of copper in breast cancer signaling pathways, emphasizing its importance in treatment strategies. Thus, targeting alterations in copper homeostasis holds promise as a strategy to combat breast cancer.

Excessive copper can induce the death of breast cancer cells, primarily through a newly identified regulatory cell death mechanism known as cuproptosis (Figure 2) (Tsvetkov et al., 2022; Wang et al., 2023e). Copper uptake into cells is predominantly mediated by copper transporter 1 (CTR1), also known as solute carrier family 31 member 1 (SLC31A1) (Kuo et al., 2001). Cellular copper homeostasis is tightly regulated by adaptive mechanisms that modulate CTR1 expression based on intracellular copper levels. In response to copper depletion, CTR1 expression is upregulated to enhance copper uptake, whereas excess intracellular copper triggers the downregulation of CTR1 to prevent toxicity (Kuo et al., 2012). After entering the intracellular environment, copper is directed to specific subcellular compartments where it is either utilized for essential biochemical processes or sequestered to avoid toxicity. This precise trafficking is mediated by a network of copper chaperone proteins, ensuring its proper distribution and regulation within the cell. Cytochrome c oxidase copper chaperone (COX17) is essential for the delivery of copper to the mitochondrial cytochrome c oxidase complex, a process crucial for sustaining copper homeostasis within the electron transport chain. This copper-dependent mechanism is vital for the proper function of oxidative phosphorylation, enabling efficient ATP production (Palumaa et al., 2004). An additional key mediator in copper distribution is the copper chaperone for superoxide dismutase (CCS), which facilitates the transfer of copper to superoxide dismutase 1 (SOD1). SOD1, a critical antioxidant enzyme, plays a pivotal role in mitigating oxidative stress by catalyzing the dismutation of superoxide radicals, thereby protecting cells from ROS (Wright, 2020). Additionally, the antioxidant 1 copper chaperone (ATOX1) facilitates the transfer of copper to the ATPase copper-transporting α and β (ATP7A and ATP7B or ATP7/B), which are transmembrane proteins responsible for copper efflux. It ensures the regulated export of excess intracellular copper, maintaining copper homeostasis and preventing toxic accumulation (Hatori and Lutsenko, 2016; Schmidt et al., 2018). ATP7A/B primarily reside in the trans-Golgi network (TGN), where they facilitate copper transport from the cytosol into the TGN lumen, ensuring copper homeostasis and delivering it to enzymes in the secretory pathway. Elevated intracellular copper levels induce the translocation of these proteins from the TGN to vesicular compartments, which fuse with the plasma membrane to export copper. Once copper levels return to normal, ATP7A and ATP7B relocate back to the TGN (Hasan et al., 2012). As a result of their critical role in copper transport, mutations in ATP7A and ATP7B disrupt copper homeostasis, leading to Menkes disease and Wilson disease, respectively (de Bie et al., 2007). Proteins regulating copper metabolism interact intricately to maintain intracellular copper homeostasis. However, disruptions in copper homeostasis can result in excessive copper accumulation within cells, potentially leading to cuproptotic cell death. Cancer cells dependent on mitochondrial respiration exhibit increased vulnerability to cuproptosis, with mitochondrial electron transport chain inhibitors suppressing this form of cell death, highlighting the link between cuproptosis and mitochondrial metabolism (Tsvetkov et al., 2022). CRISPR screens have identified key regulators of cuproptosis, with ferredoxin 1 (FDX1) emerging as a central player. FDX1, a target of the copper ionophore elesclomol, reduces Cu²⁺ to its more toxic form, Cu⁺, and regulates protein lipoylation through interaction with lipoic acid synthetase (LIAS), which catalyzes the final step of lipoic acid biosynthesis (Figure 2) (Tsvetkov et al., 2022; Tsvetkov et al., 2019). Protein lipoylation, a posttranslational modification, is essential for the function of key enzymes in the mitochondrial tricarboxylic acid (TCA) cycle, including dihydrolipoamide S-acetyltransferase (DLAT), a subunit of the pyruvate dehydrogenase complex (Rowland et al., 2018). Genetic depletion of LIAS and DLAT, like FDX1 deletion, confers resistance to cuproptosis (Tsvetkov et al., 2022). Notably, despite their crucial role in cuproptosis, levels of FDX1, LIAS, and protein lipoylation decline during the process, potentially indicating a cellular attempt to counteract excessive copper toxicity by dampening protein lipoylation—an ultimately futile strategy. These findings emphasize the pivotal role of protein lipoylation in cuproptosis. The exact mechanisms by which protein lipoylation triggers cuproptosis remain unclear. However, direct binding of copper to lipoylated DLAT has been observed, resulting in protein oligomerization during cuproptosis (Tsvetkov et al., 2022). This suggests that the resultant protein aggregates may induce a toxic gain-of-function effect, ultimately driving cuproptotic cell death (Figure 2). These findings highlight a promising area for future investigation into the complex and distinctive process of cuproptosis.

Copper complexed with disulfiram has attracted increased amounts of attention due to its anticancer effects (Zha et al., 2014). A recent study demonstrated that DSF/Cu activates ferroptosis in TNBC cells. Treatment with DSF/Cu led to increased lipid peroxidation, upregulation of HMOX1, and decreased levels of GPX4 and GSH, ultimately inducing cancer cell death through ferroptosis (Chu et al., 2023). DSF/Cu has emerged as a promising agent for inducing ferroptosis in TNBC cells, offering potential avenues for anticancer therapy (Ren et al., 2021).

The copper homeostasis gene, prion protein (PRNP), was notably downregulated in breast cancer cells, correlating with a better prognosis (Lin et al., 2023). PRNPs are involved in cancer-related signaling pathways, particularly those governing inflammatory responses and oxidative phosphorylation. PRNP overexpression markedly enhanced gefitinib sensitivity in BRCA cells. Overexpression of PRNP led to elevated ROS production following gefitinib treatment, while the ferroptosis-selective inhibitor ferrostatin-1 mitigated this increase in ROS levels in BRCA cells. PRNP expression was positively correlated with macrophages, Th1 cells, neutrophils, and B cells, while negatively correlated with NK CD56 bright cells and Th17 cells in BRCA. Single-cell analysis showed that PRNP was highly expressed in M1 phenotype macrophages, essential tumor-suppressing cells in the tumor stroma. These observations suggest that PRNP is potentially involved in ROS-mediated ferroptosis, highlighting its candidacy as a novel therapeutic target for chemotherapy and immunotherapy in breast cancer. Additionally, PRNP is correlated with a better prognosis and regulates ferroptosis following gefitinib treatment in breast cancer cells (Lin et al., 2023).

The convergence of iron and copper homeostasis is a promising avenue for inducing ferroptosis and cuproptosis in cancer cells. DSF/Cu and PRNP modulation offer potential therapeutic strategies for cancer treatment (Chu et al., 2023; Lin et al., 2023). Future research could focus on elucidating the precise mechanisms underlying the interplay between copper and iron homeostasis in regulating ferroptosis and cuproptosis in cancer cells. Additionally, exploring novel therapeutic agents/complexes that target both ferroptosis and cuproptosis could pave the way for advancements in breast cancer treatment.

Mitochondria have elevated iron concentrations (Lill and Freibert, 2020). Ferroptosis results in prominent morphological changes and dysfunction in mitochondria (Doll et al., 2017). The interaction between mitochondria and ferroptosis is well-documented, as they jointly regulate iron metabolism and lipid peroxidation (Wang J et al., 2024). While various therapeutic modalities, including endocrine therapy, immunotherapy, radiation, targeted therapy, and chemotherapy, are available for breast cancer treatment (Dong et al., 2024), interventions specifically targeting mitochondria to induce ferroptosis remain underexplored. The recently identified iron-sulfur proteins CISD1 and CISD2 facilitate the proliferation of breast cancer cells (Sohn et al., 2013). Silencing CISD1 and CISD2 or targeting breast cancer mitochondria with the mitogen derivative MAD-28 can destabilize iron-sulfur proteins, elevate mitochondrial iron accumulation, and hinder breast cancer cell growth (Bai et al., 2015). MAD-28 is highly selective, causing iron accumulation in the mitochondria of breast cancer cells only while leaving normal breast cells unaffected. This selectivity suggests that MAD-28 could be a promising agent for targeting ferroptosis and developing anticancer therapies (Dong et al., 2024). In addition, lipid metabolism, a crucial mitochondrial pathway in ferroptosis, has numerous applications in breast cancer diagnosis and treatment, with a focus on its regulation. Stearoyl-CoA desaturase-1 (SCD1) is upregulated in recurrent human breast cancer samples, indicating a poor prognosis for cancer patients. Thus, the expression of SCD1 can serve as a biomarker for breast cancer recurrence (Luis et al., 2021). Furthermore, Herceptin, also known as trastuzumab, a medication targeting HER-2 in breast cancer treatment, was found to elevate mitochondrial ROS levels in rat cardiomyocytes while reducing GPX4 expression, thereby leading to ferroptosis. The subsequent application of the ferroptosis inhibitor ferrostatin-1 successfully reversed the increase in ROS levels. This observation indicates the potential utility of ferroptosis inhibitors in mitigating cardiotoxicity associated with HER-2-positive breast cancer therapy (Sun L. et al., 2022). Furthermore, manganese superoxide dismutase 2 (SOD2), a key enzyme within the ETC, has emerged as a potential biomarker for breast cancer progression and a target for ferroptosis induction (Sui et al., 2022). Nanomaterial-based drugs, like sorafenib (Louandre et al., 2013) and simvastatin (Yao X. et al., 2021), hold considerable potential for inducing efficient ferroptosis in breast cancer cells without systemic toxicity (Li K. et al., 2022; Sang M et al., 2019; Yao X. et al., 2021).

In conclusion, mitochondria serve as central regulators of ferroptosis in breast cancer, and targeting mitochondrial metabolism represents a promising avenue for inducing ferroptosis in specific breast cancer subtypes. However, further research is warranted to elucidate the precise underlying mechanisms and optimize therapeutic strategies targeting mitochondrial pathways for effective breast cancer treatment.

Mitochondria are pivotal copper-dependent organelles responsible for energy production through the indispensable cuproenzyme cytochrome c oxidase (CCO) (Carr and Winge, 2003). Disturbances in intracellular copper homeostasis, including loss-of-function mutations in genes crucial for copper regulation, invariably result in lethal genetic disorders such as Wilson disease and Menkes disease (Członkowska et al., 2018; Tümer and Møller, 2010). The mitochondrial TCA cycle is pivotal in the process of cuproptosis, where protein lipoylation is confined to four specific proteins (DBT, GCSH, DLST, and DLAT) involved in this cycle. This process is primarily mediated by the mitochondrial carrier family (MCF) (Chen L. et al., 2022; Tang et al., 2022).

Cuproptosis initiates with the accumulation of copper in the cytoplasm and organelles. This prompts the clustering of mitochondrial lipoylated modules and the destabilization of Fe-S cluster proteins essential for mitochondrial function (Chen L. et al., 2022; Tang et al., 2022). Cuproptosis is intricately connected to mitochondrial respiration, and the status of mitochondrial respiratory function impacts its susceptibility (Tang et al., 2022; Yuan et al., 2022). Recently, significant attention has been directed toward understanding the role of mitochondria and cuproptosis in breast cancer (Gururaja Rao, 2017; Liu X. et al., 2023; Porporato et al., 2018). Breast cancer cells undergo metabolic reprogramming, shifting from glycolysis to increased mitochondrial oxidative phosphorylation (OXPHOS) and metabolism, supporting rapid proliferation and metastasis (Li and Li, 2021). Mitochondrial dynamics exhibit flexibility, transitioning between different forms to adapt to microenvironmental changes and therapeutic stress, aiding cancer cell survival (Avagliano et al., 2019). Breast cancer stem cells (CSCs) and circulating tumor cells (CTCs) rely heavily on mitochondrial metabolism and OXPHOS for tumor initiation, metastasis, and treatment resistance (Wedam et al., 2023). Key oncogenes and tumor suppressors, such as Myc, TP53, PIK3CA, and Bcl-2 family proteins, regulate mitochondrial metabolism, contributing to tumor progression (Wedam et al., 2023). Mitochondrial dysfunction and alterations in metabolic pathways, such as those involving lipids, amino acids, and the TCA cycle, contribute to drug resistance, suggesting that targeting these pathways could enhance chemotherapy efficacy (Li and Li, 2021; Wedam et al., 2023). Importantly, targeting mitochondrial metabolism through the induction of cuproptosis represents a significant research avenue for cancer therapy, including breast cancer treatment. Breast cancer cells that rely on mitochondrial respiration are particularly susceptible to cuproptosis induction (Ai L. et al., 2024; Xie et al., 2023). Targeting mitochondria to induce cuproptosis in breast cancer cells leverages the role of copper in triggering cell death (Wang J. et al., 2024).

In breast cancer, elevated GSH levels are frequently observed, especially in TNBC, potentially attributed to estrogen-mediated downregulation of transferrin receptor expression (Ge A. et al., 2024). Such heightened GSH levels contribute to resistance against ferroptosis and other cell death modalities, fostering cancer progression and therapeutic resistance (Liu Y. et al., 2022). Notably, GSH-rich environments in breast cancer cells counteract the cytotoxic effects of anticancer agents like cisplatin and paclitaxel by neutralizing ROS, thereby conferring treatment resistance. However, interventions targeting GSH metabolism, such as benzothiazole-mediated GSH inhibition, have demonstrated promising efficacy in sensitizing breast cancer cells to conventional treatments (Ge A. et al., 2024). Therefore, manipulating GSH levels holds therapeutic promise in breast cancer management. Strategies aimed at GSH depletion, achieved through inhibition of the cystine/glutamate antiporter or GPX4 inactivation, induce ferroptosis and enhance treatment efficacy (Ge A. et al., 2024; Xu C. et al., 2023). Reducing GSH levels has been shown to alleviate radiation resistance, particularly through hypoxia-inducible factor-1 (HIF-1) mediated metabolic reprogramming. Clinical implications include the development of therapeutic approaches targeting GSH metabolism, combining therapies integrating ferroptosis inducers with conventional treatments, and identifying GSH levels and ferroptosis-related gene expression as predictive biomarkers (Xu C. et al., 2023; Yang F. et al., 2023; Zhou T. J. et al., 2024). This comprehensive understanding of the interplay between GSH metabolism and ferroptosis offers novel avenues for refining breast cancer therapy and improving patient outcomes.

Ferroptosis inducers like sorafenib and erastin downregulate GSH synthesis, decreasing intracellular GSH levels. This refers to increased cuproptosis, compromising copper-chelating capacity and promoting labile copper accumulation. Restoring GSH levels reversed the sensitizing effect of ferroptosis inducers on copper-induced cytotoxicity and cuproptosis. Combining GSH synthesis inhibitors such as buthionine sulfoximine with copper ionophores could be a potential therapeutic approach for inducing cuproptosis in breast cancer cells. However, specific studies are needed to explore their efficacy and safety (Mao et al., 2024; Wang W. et al., 2023; Wang Y. et al., 2024).

The interaction between autophagy and ferroptosis in breast cancer is multifaceted, with autophagy exhibiting both promoting and protective roles in ferroptosis induction. Autophagy facilitates ferroptosis by promoting iron accumulation and lipid peroxidation, which are crucial events in ferroptosis initiation. Specific autophagic processes such as ferritinophagy and lipophagy release iron and lipids, promoting ferroptosis (Gao et al., 2016; Li J. et al., 2021; Liu et al., 2020). Conversely, inhibition of autophagy-related genes or cargo receptors impedes ferritin degradation, thus preventing ferroptosis onset. Moreover, ferroptosis inducers like erastin and sulfasalazine can induce autophagy in breast cancer cells. This induction of autophagy, however, seems to diminish the efficacy of ferroptosis inducers in killing breast cancer cells. Inhibiting autophagy in such conditions sensitizes breast cancer cells to ferroptosis inducers (Chipurupalli et al., 2023). The interplay among ferroptosis, autophagy, and iron metabolism underscores their interconnectedness in breast cancer pathophysiology.

Both ferroptosis and autophagy are driven by iron-dependent ROS generation, and alterations in intracellular iron levels and ferritin expression contribute to their respective cell death mechanisms. Heme oxygenase-1, which increases the cellular free iron pool, can further enhance ferroptosis in breast cancer cells (Chipurupalli et al., 2023; Lee et al., 2023; Ma et al., 2017; Xu C. et al., 2023). Moreover, in pancreatic cancer, transmembrane protein 164 (TMEM164) has been shown to activate autophagy, leading to the degradation of ferritin, GPX4, and lipid droplets. This process increases iron accumulation and lipid peroxidation, thereby promoting ferroptosis in cancer cells (Liu J. et al., 2023). Autophagy, therefore, plays a pivotal role in facilitating ferroptosis in cancer therapy. Interestingly, copper not only induces proteotoxic stress but also drives ferroptosis by directly binding to GPX4, resulting in the formation of GPX4 aggregates. These aggregates undergo autophagic degradation, further inducing ferroptosis (Xue et al., 2023b). Furthermore, in glioblastoma (GBM), inhibiting autophagy increases the sensitivity of GBM stem cells to temozolomide treatment by inducing ferroptosis (Buccarelli et al., 2018). Conversely, in hepatocellular carcinoma, autophagy driven by PNO1, a known ferroptosis inhibitor, enhances glutamate synthesis, activating system Xc− and ultimately preventing ferroptosis (Hu X. et al., 2022). In non-small cell lung cancer, curcumin induces ferroptosis through the activation of autophagy (Tang X. et al., 2021). These studies suggest that autophagy can either promote or suppress ferroptosis depending on the cancer type, which may be influenced by factors such as tumor heterogeneity or varying cellular environments. Further research is needed to clarify these interactions. Therapeutically, simultaneously targeting both ferroptosis and autophagy pathways has emerged as a promising strategy to overcome treatment resistance in breast cancer. Combination therapies incorporating ferroptosis inducers and autophagy modulators can potentially improve treatment effectiveness.

Disturbance of copper homeostasis modulates ferroptosis and cuproptosis and initiates autophagy pathways (Li Y. et al., 2021; Xue et al., 2023a; Yang et al., 2021). The intracellular accumulation of copper activates transcription factor EB (TFEB), upregulates ATG5, sequestosome 1 (SQSTM1), and microtubule-associated protein 1 light chain 3 (MAP1LC3) expression, and modulates the AMPK-mTOR pathway, thereby stimulating autophagy (Xue et al., 2023a; Yang et al., 2021). Inhibition of the copper transporter SLC31A1 in pancreatic cancer cells results in decreased intracellular copper concentrations and enhances autophagy (Yu et al., 2019). However, the interplay between cuproptosis and autophagy in breast cancer remains ambiguous, yet it is postulated that disruptions in copper homeostasis may promote autophagy. Further investigation into this crosstalk is warranted to elucidate the underlying mechanisms and implications for cancer pathogenesis and treatment strategies.

Over the past decade, research has linked ferroptosis to chemotherapy resistance in cancer, highlighting its potential as a therapeutic strategy. Key regulators of ferroptosis, including proteins and enzymes involved in iron metabolism, lipid peroxidation, and the system Xc–pathway, play critical roles in modulating chemotherapy resistance. In TNBC, anthracyclines often demonstrate limited efficacy due to chemotherapy resistance and notable side effects. Studies suggest that inducing ferroptosis may enhance the sensitivity of TNBC cells to these agents, providing a promising approach to improve therapeutic outcomes (Luo et al., 2022; Zhao J. et al., 2023). Recent advancements in research have identified several chemotherapeutic agents that can induce ferroptosis as a mechanism for their anti-cancer effects. Notable examples include cisplatin, temozolomide, orlistat, and sorafenib. These drugs exploit the ferroptotic pathway to enhance their efficacy against various cancer types, presenting a novel strategy for improving treatment outcomes (Mou et al., 2019; Yin et al., 2022). Anomanolide C has been shown to inhibit the progression and metastasis of TNBC by enhancing the ubiquitination of the GPX4 protein, leading to autophagy-dependent ferroptosis (Chen Y-M. et al., 2023). This research highlights the potential of targeting ferroptosis as a strategy to sensitize tumors to chemotherapy in future cancer therapies. Saponin formosanin C (FC), a potent ferroptosis inducer from Paris formosana, enhances ferritinophagy and chemosensitivity to cisplatin in TNBC cells (Chen H-C. et al., 2022), while gallium maltolate (GaM) demonstrates synergistic anti-tumor effects with cisplatin, leading to TNBC cell death by impeding cell cycle progression and proliferation (Chen H-C. et al., 2023). Propofol, traditionally an anesthetic, has been shown to inhibit TNBC cell proliferation and potentiate doxorubicin and paclitaxel’s effects through the p53-SLC7A11-GPX4 pathway (Sun C. et al., 2022; Xu et al., 2020). Additionally, SOCS1, a new target for TNBC treatment, regulates cisplatin resistance and tumor progression (Wang et al., 2023d). A recent study provides new evidence that doxorubicin (DOX) exerts its anti-cancer effects, in part, by inducing ferroptosis. A critical role for DnaJ heat shock protein family (Hsp40) member C12 (DNAJC12) in breast cancer chemotherapy resistance was identified, as DNAJC12 was shown to suppress both DOX-induced ferroptosis and apoptosis, contributing to treatment resistance. Moreover, the DNAJC12/HSP70/AKT signaling axis appears to mediate this resistance by inhibiting these cell death pathways. Additionally, the findings further support the potential of AKT inhibitors or HSP70 inhibitors in reversing this resistance mechanism. This may offer a new perspective on overcoming DOX resistance in estrogen receptor-positive (ER+) breast cancer or other molecular subtypes with high DNAJC12 expression. These results suggest that targeting this axis may enhance the efficacy of DOX by restoring sensitivity to ferroptosis and apoptosis (Hu et al., 2024). Leveraging ferroptosis to enhance the efficacy of adjuvant chemotherapies and counteract chemotherapy resistance offers a promising therapeutic approach for treating breast cancer.

Numerous studies indicate that radiotherapy can exert anticancer effects by inducing ferroptosis. Ionizing radiation (IR) initiates cell death through several mechanisms, primarily by generating ROS and upregulating ACSL4, which leads to lipid peroxidation and triggers ferroptosis (Lei G. et al., 2020). A nanomedicine, BZAMH (Zeng et al., 2023), based on a metal-organic framework and combining high-Z element radio-sensitization, induces both ferroptosis and apoptosis in TNBC by disrupting GSH production with L-buthionine-sulfoximine (BSO) and promoting the Fenton reaction with supplied ferrous ions (Zeng et al., 2023). Additionally, iron-saturated lactoferrin (Holo-Lf) enhances ROS generation, damages DNA, and alleviates hypoxia in TNBC cells, improving radiosensitivity through disrupted iron metabolism and promoting ferroptosis (Zhang Z et al., 2021).

The TME has an immunosuppressive effect and lipid metabolism, a key feature of the TME, is closely linked to ferroptosis through lipid peroxidation (Mao et al., 2021; Xia et al., 2021). This intricate crosstalk between ferroptosis and the TME plays a crucial role in determining immunotherapy efficacy or resistance (Tang D. et al., 2021; Wang et al., 2021). Numerous studies demonstrate that ferroptosis significantly influences the immune response by affecting the activity of immune cells (Kim et al., 2022; Liao et al., 2022). In the TME, different immune cell subtypes, such as T cells, B cells, granulocytes, and monocytes, may experience spontaneous ferroptosis, which in turn impacts the overall immune response (Xu S. et al., 2021). In recent years, immunotherapy has emerged as a promising approach for TNBC treatment, with studies indicating its potential to induce ferroptosis. In TNBC, the LAR subtype, which expresses the androgen receptor, demonstrates increased levels of oxidized phosphatidylethanolamine and alterations in glutathione metabolism, especially involving GPX4. Notably, the inhibition of GPX4 can trigger ferroptosis in this subtype (Yang F. et al., 2023). Research has shown that inhibiting GPX4 not only triggers ferroptosis in tumors but also boosts anti-tumor immunity. The combination of a GPX4 inhibitor with anti-PD1 therapy is more effective than monotherapy (Fan Y et al., 2023). Furthermore, protein arginine methyltransferase 5 (PRMT5) plays a crucial role in regulating ferroptosis, as it methylates and stabilizes Kelch-like ECH-associated protein 1 (KEAP1), a ubiquitinating enzyme that blocks the NRF2/HO-1 pathway, increasing TNBC resistance to both ferroptosis and immunotherapy (Wang et al., 2023f). This highlights PRMT5 as a potential therapeutic target, suggesting that combining immunotherapy with PRMT5 inhibitors could enhance treatment effectiveness. Additionally, a newly designed small-molecule photosensitizer, Ir(III) photosensitizer (IrFc1) (Ling et al., 2022), coupled with transferrin and ferrocene, can promote ferroptosis in TNBC cells through a self-amplifying mechanism, leading to lipid oxidation and immunogenic cell death upon irradiation. TNBC cells exhibit higher tumor-infiltrating lymphocytes (TILs) and PD-L1 levels compared to other breast cancer subtypes, and PD-L1 inhibitors like atezolizumab and pembrolizumab have demonstrated efficacy in slowing disease progression in advanced metastatic TNBC (Adams et al., 2020; Jiang et al., 2021; Zhang X. et al., 2022). However, a limited number of patients respond effectively, primarily due to drug resistance and the absence of reliable biomarkers for patient stratification. Moreover, research by Zhou et al. has identified TYRO3 as a contributor to anti-PD-L1 resistance through the inhibition of ferroptosis via the AKT/NRF2 axis, suggesting that targeting TYRO3 with receptor tyrosine kinase inhibitors to restore ferroptosis may help overcome resistance and improve survival in aggressive TNBC cases (Jiang et al., 2021). Shao and colleagues explored the heterogeneity of ferroptosis phenotypes in different TNBC subtypes. They found increased iron metabolism in the MES subtype and highlighted ferroptosis-related pathways in the LAR subtype, while the BLIS and IM subtypes showed no distinct ferroptosis characteristics. GPX4 production and ferroptosis inhibition primarily occur through androgen receptor (AR) signaling. Thus, combining GPX4 inhibitors with immune checkpoint inhibitors may offer a novel treatment strategy for tumors resembling the LAR subtype (Jiang L. et al., 2023).

Utilizing nanoparticles characterized by their small size and low toxicity provides a solution, as these particles can effectively carry ferroptosis inducers (FINs). More importantly, nanoparticles can be engineered for targeted drug delivery to tumor cells, thereby minimizing the detrimental effects on healthy cells. Employing nanoparticle-loaded FINs for targeted transport could significantly enhance the efficacy of cancer treatments (Qi X. et al., 2022). Recent research has focused on inducing ferroptosis in breast cancer through various innovative drug delivery systems. Notable advancements include folate-labeled exosomes that enhance ferroptosis by depleting glutathione and increasing ROS in MDA-MB-231 cells. Other studies have developed nanocomposites and carrier-free nano drugs that combine ferroptosis inducers with autophagy promoters, demonstrating potent anticancer effects. These approaches highlight the potential of targeted therapies to improve breast cancer treatment outcomes (Li Z. et al., 2020).

A self-assembled nanosystem comprising drug-organic-inorganic components (DFTA) demonstrates effective inhibition of ER+ breast cancer progression. This system utilizes DOX as a chemotherapeutic agent, ferric chloride (FeCl₃) as a ferroptosis inducer, and tannic acid (TA) to activate superoxide dismutase (SOD). This combination triggers a cascade reaction that generates ROS and significantly depletes GSH levels. Furthermore, integrating photothermal therapy (PT) enhances ROS production efficiency, paving the way for a synergistic approach combining chemotherapy, PT, and ferroptosis in the treatment of ER+ breast cancer (Xiong et al., 2019). Yttrium oxide nanoparticles (Y2O3-NPs) selectively induce cytotoxicity in MDA-MB-231 cells by generating oxidative stress, elevating ROS levels, causing DNA damage, and triggering apoptosis and ferroptosis through upregulation of CASP3, CASP8, and HO-1, and downregulation of BCL2 (Emad et al., 2023). The BSOandOXA@MOF-LR formulation exhibits strong tumor-suppressive properties and significantly enhances survival rates in 4T1 tumor xenograft mice. This effect is attributed to the combined action of amplified ferroptosis and the elimination of GSH, which sensitizes cells to apoptosis (Rao et al., 2023). A novel nanoprodrug (DOX@Fc-SS-ATRA NP) combining ferrocene, a differentiation inducer (ATRA), and doxorubicin, enhances TNBC therapy by promoting ferroptosis via the Fenton reaction (Wu C et al., 2023). Furthermore, a small molecule nanoprodrug delivering chemotherapeutics (CPT), Fc, and the GPX4 inhibitor RSL3 inhibits TNBC growth and metastasis through inducing apoptosis and ferroptosis, with Fc and RSL3 amplifying chemotherapy efficacy (Chen et al., 2023).

Advances in pharmacological technologies have led to the development of innovative nanomaterials for breast cancer treatment, valued for their high efficiency and safety. This also includes mitochondria-targeted nanomaterials that deliver ferroptosis-inducing drugs, offering a promising approach to improve therapeutic outcomes. A magnetic nano-photosensitizer complex CSO-SS-Cy7-Hex/SPION/Srfn, capable of accelerating redox reactions and the Fenton reaction, enhances concentration of iron and LPO with reducing GSH levels simultaneously. Through analysis of EMT-related experimental findings, it was observed that the CSO-SS-Cy7-Hex/SPION/Srfn self-assembled complex induced ferroptosis, effectively countering multidrug resistance, invasion, and metastasis in breast cancer (Sang M. et al., 2019). Simvastatin, another ferroptosis-inducing drug, also demonstrated high efficacy with the use of novel nanomaterials. By inhibiting 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase, it regulates cholesterol metabolism via Fe3O4@PCBMA magnetic nanoparticles, downregulating both the mevalonate and GPX4 pathways. This induces ferroptosis in TNBC cells without causing liver or kidney toxicity. These pathways are further linked to mitochondrial glycometabolism and lipid metabolism (Yao X. et al., 2021). A Cu-tetra (4-carboxyphenyl) porphyrin chloride (Fe(III)) Cu-TCPP(Fe)-based MOF nano-system, integrated with Au nanoparticles and loaded with RSL3, blocks GSH biosynthesis by disrupting the pentose phosphate pathway, boosting RSL3-induced ferroptosis (Li K. et al., 2022). Though still in research, these nanomaterials offer promising potential for future BRCA therapies. The incorporation of various ferroptosis-inducing agents into nanoplatforms enhances anticancer efficacy through improved targeted delivery and greater tissue permeability of nanocarriers. Recent reviews highlight these advancements in nanotechnology as promising strategies for breast cancer treatment. Moreover, a recent study demonstrated that Boswellia carterii n-hexane extract (BCHE) significantly inhibited the viability of human breast cancer cells and displayed potent in vivo anti-breast cancer activity without notable toxicity, inducing ferroptosis by upregulating transferrin expression and intracellular Fe²⁺ levels, downregulating glutathione peroxidase 4 (GPX4), and promoting ROS mediated lipid peroxidation in both breast cancer cells and tumor-bearing mice, suggesting BCHE as a potential therapeutic candidate for ferroptosis-targeted breast cancer treatment (Xie et al., 2024). Furthermore, a study shows that oridonin (ORI), the main active component derived from the Chinese herbal plant Rabdosia rubescens, boosts the anti-proliferative effect of RSL3 on breast cancer cells by facilitating ferroptosis. Mechanistically, it enhanced RSL3-induced ferroptosis in breast cancer cells through activation of the JNK/Nrf2/HO-1 signaling pathway. The combination therapy of RSL3 and ORI suppressed breast cancer cell proliferation, resulting in the accumulation of lipid peroxidation products and iron ions (Ye et al., 2024). In recent years, GSK-3β has been identified as a key tumor suppressor involved in maintaining redox balance. Research by Wang et al. demonstrated that silencing GSK-3β in MDA-MB-231 cells leads to a decrease in DMT1 levels, resulting in lower intracellular ferrous iron accumulation. This reduction subsequently diminishes the sensitivity of these cells to erastin-induced ferroptosis, suggesting that GSK-3β plays a vital role in promoting ferroptosis sensitivity in breast cancer cells (Wang L. et al., 2021). Furthermore, high expression of FADS1/2, enzymes involved in PUFA biosynthesis, was associated with poor prognosis in TNBC and sensitivity to ferroptosis inducers; however, targeting FADS1/2 conferred resistance, which could be reversed by restoring PUFA levels, and inhibiting lipid droplet formation further enhanced ferroptosis, as demonstrated in preclinical models and a patient cohort (Lorito et al., 2024). Moreover, research has shown that BET inhibitors (JQ1 and I-BET151) exert anti-cancer effects in breast cancer by inducing ferroptosis, with NCOA3, as a coactivator, interacting with NR5A2 to counteract BETi-induced ferroptosis. Mechanistically, NR5A2 and NCOA3 cooperate to upregulate NRF2, a transcription factor regulating antioxidant gene expression, and inhibiting NR5A2 or NCOA3 enhances BETi’s anti-cancer effects both in vitro and in vivo. These findings suggest that targeting NR5A2/NCOA3 in combination with BET inhibitors could provide a novel therapeutic strategy for breast cancer treatment (Qiao et al., 2020).

Elevated intracellular copper accumulates in the mitochondria, where it interacts with lipoacylated proteins, causing the oligomerization of DLAT and destabilizing the Fe-S cluster proteins. This disruption leads to cancer cell death, termed cuproptosis (Kahlson and Dixon, 2022). This mechanism has prompted the exploration of copper ionophores, such as DSF and ES, which increase intracellular copper levels and could potentially treat breast cancer. These ionophores form lipophilic complexes with copper, enhancing its cellular accumulation, and thus showing promise for cancer therapy (Lelièvre et al., 2020).

The anti-cancer effects of disulfiram, particularly in breast cancer, have been extensively investigated. DSF, a well-known aldehyde dehydrogenase (ALDH) inhibitor, has demonstrated significant anti-cancer properties, particularly against ALDH-positive breast cancer stem cells (Ni Y. L. et al., 2022). In addition to its targeting of these stem cells, DSF enhances ROS accumulation, thereby effectively overcoming cisplatin resistance in breast cancer cell lines. Such insights may shape future chemotherapeutic strategies (Yang et al., 2019). Research conducted by Swetha et al. indicates that the combination of DSF with docetaxel-loaded nanoparticles enhances the sensitivity of drug-resistant breast cancer cells to docetaxel. This sensitization occurs through the inhibition of the drug efflux pump P-glycoprotein, as well as the targeting of cancer stem cells (CSCs) (Swetha et al., 2023). Zheng et al. demonstrated that DSF enhances PD-L1 expression in TNBC cells, significantly improving the response of mouse breast cancer models to anti-PD-1 antibody therapy. This suggests that combining DSF with anti-PD-1 therapy could be a promising strategy for enhancing TNBC treatment outcomes (Zheng et al., 2021). Furthermore, a combination therapy evident against MCF-7 breast cancer cells, has proven to have a synergistic effect of DOX with hydrazine (Hyd) and DSF to lower the dose of the chemotherapeutic drug (Lafi et al., 2023). DSF couples with copper as a copper ionophore to produce the metabolite bisdiethyldithiocarbamate-copper (CuET), facilitating the transport of copper across the cell membrane (Lu et al., 2021). In addition, cellular damage in breast cancer cell lines resulting from DSF/Cu is associated with apoptosis, ferroptosis, and cuproptosis (Table 3). DSF/Cu inhibits the proliferation of breast cancer stem cells and potentiates the cytotoxic effects of paclitaxel, likely through a combined mechanism of ROS generation and NF-κB pathway suppression (Yip et al., 2011). Acidic pH significantly enhances the cytotoxic effects of the DSF–Cu complex in breast and colon cancer cells. This enhanced toxicity is linked to alterations in cell metabolism, modulation of AKT kinase and NF-κB pathways, and elevated production of ROS (Navrátilová et al., 2013). However, the current clinical effectiveness of DSF/Cu remains ambiguous. Notably, findings from a prospective clinical trial examining DSF paired with Cu for metastatic prostate cancer revealed that DSF was rapidly converted to the inactive metabolite Me-DDC, which resulted in no observable clinical benefits (Zhang T. et al., 2022). In contrast, a Phase II trial indicated that the combination of disulfiram with cisplatin and vinorelbine led to rare long-term survival in two-stage IV lung cancer patients (Nechushtan et al., 2015). Additionally, two separate clinical trials investigating the combination of DSF and Cu for patients with liver metastases (Kelley et al., 2021) and recurrent gliomas (Werlenius et al., 2023) also failed to show significant survival advantages. These divergent results emphasize the need for further research to optimize disulfiram’s therapeutic applications and assess its efficacy across different cancer types, including breast cancer.

ES, a lipophilic copper-binding compound, is capable of chelating extracellular Cu²⁺ ions to form a complex that enables the efficient transport of copper into cells (Gohil, 2021; Guthrie et al., 2020). Once inside the cells, ES exerts anticancer effects primarily by targeting mitochondrial metabolism, inducing oxidative stress, and reducing the expression of CSC markers like CD133 and ALDH (Harrington et al., 2020). Additionally, recent evidence underscores its ability to induce copper-dependent cell death (Tsvetkov et al., 2019), reinforcing its role as a promising agent in breast cancer therapy (Alli and Ford, 2012). Serum lactate dehydrogenase (LDH) levels are closely linked to mitochondrial metabolism, with lower LDH levels correlating to increased sensitivity to ES (Zheng et al., 2022). This observation has significant implications for the use of LDH as a predictive biomarker in cuproptosis-targeting treatments. Notably, in a phase III clinical trial, ES combined with paclitaxel showed limited success overall but demonstrated enhanced efficacy in melanoma patients with lower LDH levels (O'Day et al., 2013), suggesting that mitochondrial metabolism plays a pivotal role in cuproptosis activation. Earlier trials, such as a phase II study, had shown that the addition of ES to paclitaxel significantly prolonged progression-free survival (PFS) in melanoma patients by 41.7%, highlighting its potential as an anti-cancer agent (O'Day et al., 2009). Furthermore, a phase I trial in patients with refractory solid tumors, including Kaposi sarcoma and ovarian cancer, provided partial responses (Berkenblit et al., 2007), further suggesting that ES copper-dependent mechanism could enhance therapeutic outcomes. However, despite promising early-phase results, ES has not consistently demonstrated robust clinical benefits. One potential reason for this is its inability to sufficiently elevate copper levels in tumor cells when used as a monotherapy. This reinforces the need for combinatory strategies and highlights the importance of biomarkers like LDH to optimize patient selection and treatment efficacy.

Copper plays a complex and dual role in tumor development. Elevated Cu levels are linked to enhanced tumor cell proliferation and growth, which suggests that tumor cells may employ certain mechanisms to resist cuproptosis. Consequently, targeting Cu homeostasis with small molecular compounds offers a promising strategy to induce or heighten tumor cell sensitivity to cuproptosis. Several recent studies have identified small molecular compounds capable of inducing this copper-dependent cell death. For example, Yang et al. demonstrated that zinc pyrithione disrupts intracellular Cu balance and triggers DLAT oligomerization in TNBC cells, which may contribute to their increased chemosensitivity (Yang X. et al., 2023). Recent research highlights that ferroptosis inducers also potentiate cuproptosis in cancer cells. For example, Sorafenib, the first multi-tyrosine kinase inhibitor approved for various cancers, and erastin, a well-known ferroptosis inducer, have been shown to exacerbate cuproptosis in liver cancer cells (Wang W. et al., 2023), providing new avenues for combined therapeutic strategies. In contrast to copper ionophores, which require copper supplementation, small-molecule compounds like ZnPT that disrupt intracellular copper homeostasis present a more refined therapeutic approach. These compounds can induce cuproptosis in tumor cells without introducing excess copper, minimizing the risk of metal ion imbalances and reducing potential side effects associated with metal toxicity. This method highlights the potential of targeted treatments that leverage intrinsic cellular mechanisms while mitigating adverse effects during therapy.

Copper complexes exhibit diverse catalytic and electrochemical properties (Balsa et al., 2023), positioning them as promising candidates for breast cancer therapy. These complexes exert tumor-inhibitory effects by generating ROS, depleting intracellular glutathione, impairing proteasome function, and inducing DNA damage (Ji et al., 2023), all of which contribute to the selective targeting of cancer cells. Through these mechanisms, copper complexes disrupt cellular homeostasis, promoting cancer cell death and offering potential therapeutic advantages over traditional treatments. Studies have demonstrated that copper complexes like CuHL1 and Cu-PLN inhibit the growth of TNBC cells by triggering cuproptosis. CuHL1 achieves this by downregulating DLAT expression via copper-induced protein lipoylation, while Cu-PLN contributes to cancer cell death by generating ROS, causing DNA damage, and disrupting mitochondrial function, ultimately affecting cellular metabolism (Mukherjee et al., 2023). The study by Xu et al. explored a copper-based complex called HA-Cu, synthesized from disulfonamide-dimethylpyrimidine-phenanthroline-metal, which showed potent inhibitory effects on TNBC (Xu et al., 2024). This complex was effective both in vitro and in vivo, suppressing tumor growth through a synergistic mechanism. It combined antiproliferative, antiangiogenic, anti-inflammatory, and pro-apoptotic properties, inducing cuproptosis in MDA-MB-231 cells by reducing FDX1 expression and increasing HSP70 expression (Xu et al., 2024). Similarly, He et al. developed a copper-chelated cyanine dye to deliver copper ions in various oxidation states, which were tested in 4T1 cells and 4T1 tumor-bearing mice (He et al., 2024). This approach further explored the role of copper in combating TNBC, reinforcing the idea that copper, through various mechanisms like cuproptosis and regulation of key cellular pathways, can be a promising strategy in breast cancer treatment​. These mechanisms highlight the potential of copper complexes as targeted therapies against aggressive cancers like breast cancer.

Over the past 3 decades, there has been a significant expansion of research in the field of cancer nanotherapeutics (Fan D. et al., 2023). Drugs can be transformed into nanotherapeutics through processes such as dissolution, adsorption, encapsulation, or binding to nanomaterials. These nanotherapeutics leverage unique tumor characteristics such as acidic microenvironments, high levels of GSH and ROS, or tumor-specific surface markers to achieve targeted accumulation and controlled release at the tumor site. This strategic targeting enhances therapeutic precision, significantly reducing off-target effects and the toxicity associated with conventional cancer treatments. The therapeutic effectiveness of chemotherapy can be further improved by combining it with nanocarrier-based methods like photodynamic therapy (PDT), photothermal therapy (PTT), or chemodynamic therapy (CDT), enhancing the overall anticancer efficacy. CDT leverages the Fenton reaction to generate hydroxyl radicals (⋅OH) from overexpressed H₂O₂ within tumor cells, effectively inducing oxidative stress and cell death without the need for external energy sources (Zhao F. et al., 2023).

Given the relatively low selectivity of copper ionophores for tumor cells, employing nanoparticle-based delivery systems can more effectively direct copper to tumor tissues (Zhang C. et al., 2024). This approach heightens cuproptosis activity within tumors while minimizing harm to healthy tissues. Since the identification of cuproptosis, research has increasingly focused on its potential therapeutic applications, particularly in nanoparticle-facilitated copper delivery systems. Researchers have focused on precisely delivering copper, copper ionophores, and other anticancer agents like chemotherapeutic drugs and siRNA to enhance nanomedicine-induced cuproptosis. This targeted approach synergistically increases breast tumor cell damage by sensitizing them to cuproptosis while simultaneously activating additional therapeutic mechanisms (Table 3).

Cu-GA nanoparticles (NPs), which are composed of Cu²⁺, gallic acid, and polyvinylpyrrolidone, have been shown to induce cuproptosis and apoptosis by depleting intracellular GSH levels and increasing ROS production. When combined with CDT, this approach significantly suppresses tumor growth, demonstrating a synergistic effect that enhances therapeutic efficacy (Zhao F. et al., 2023). Similarly, Cu2O@CuBTC-DSF@HA nanocomposites (CCDHs), constructed from Cu₂O, trimesic acid, disulfiram, and hyaluronic acid, offer a unique therapeutic approach by promoting cuproptosis synergistically, without inducing apoptosis. This mode of action increases anti-tumor efficacy while minimizing toxicity, making it a promising strategy for breast cancer treatment (Zhong et al., 2023). SonoCu nanoparticles, a combination of Cu²⁺, a zeolitic imidazolate framework, perfluorocarbon, chlorine-6, and oxygen, have been integrated with sonodynamic therapy (SDT). This system induces cuproptosis specifically in tumor cells while sparing normal cells, leading to strong biosafety and favorable anti-tumor outcomes, which highlights its potential for targeted cancer therapies (Chen K. et al., 2023). HNPs, comprised of DTPH, Cu²⁺, disulfiram, hyaluronan, and artemisinin, also show promise. These particles deplete GSH through their disulfide bonds, sensitizing cancer cells to cuproptosis. By simultaneously inducing cuproptosis, ferroptosis, and apoptosis, HNPs can effectively suppress tumor growth, particularly in 4T1 breast cancer model (Xu W. et al., 2023). CS/MTO-Cu@AMI, a nanocomplex consisting of mitoxantrone, Cu²⁺, amiloride, and chondroitin sulfate, induces cuproptosis and disrupts mitochondrial function in 4T1 breast cancer tumors. By activating the AMPK pathway, this formulation promotes PD-L1 degradation, effectively reducing immune evasion by cancer cells. Furthermore, CS/MTO-Cu@AMI enhances anti-tumor immunity by stimulating the cGAS-STING pathway, which plays a critical role in promoting immune surveillance and response against tumors, making it a promising candidate for combination therapies targeting immune checkpoints (Tian et al., 2023). CuX-P binds to PD-L1 on tumor cells, leading to its internalization, and subsequently triggering cuproptosis. When combined with laser treatment, this process amplifies the anti-tumor immune response by enhancing immune system activation (Liu T. et al., 2023). CuMoO4 Nanodots use prolonged photothermal therapy (PTT) to simultaneously induce ferroptosis and cuproptosis in 4T1 and MCF-7 tumors. This dual-action approach stimulates an immune response through immunogenic cell death (ICD), enhancing its effectiveness as a therapeutic strategy (Zhang J. et al., 2023). ZCProP specifically targets mitochondria, delivering copper ions and prodigiosin, which synergistically induce cuproptosis, ferroptosis, and apoptosis (Deng et al., 2024). The LDH/HA/5-FU nanosheets are designed to selectively target tumor cells, facilitating the rapid release of Cu²⁺ and 5-FU, which together induce apoptosis and cuproptosis while enhancing immune responses. This dual delivery system represents a promising approach that combines Cu-based CDT with chemotherapy for solid tumor treatment (Xia et al., 2024). Complementing this, E-C@DOX NPs effectively inhibit tumor cell stemness and survival pathways, utilizing Cu to disrupt mitochondrial function and trigger cuproptosis, which counters ATP-dependent drug efflux mechanisms, thus reversing DOX resistance (Lu et al., 2024). Additionally, D-CuxOS@Fe–MOF enhances oxidative stress, robustly inducing both ferroptosis and cuproptosis for improved therapeutic response against cancer (Hao et al., 2024). Cu@CDCN further enhances this synergy by integrating photocatalytic hydrogen therapy with anchored Cu²⁺, inducing cuproptosis and mitochondrial dysfunction, ultimately inhibiting tumor cell proliferation and significantly suppressing tumor growth (Ding et al., 2023).

Moreover, ECPCP substantially extends the circulation time of the elesclomol–Cu complex, promoting its accumulation at tumor sites and activating cuproptosis. The complex’s Cu²⁺-driven Fenton-like reactions, alongside ROS production from cinnamaldehyde, disrupt redox balance, triggering ICD and enhancing synergy with immunotherapy (Wu et al., 2024). Furthermore, Au@MSN-Cu/PEG/DSF, CJS-Cu NPs, PDA-DTC/Cu NPs, Cu-LDH, Cu-DBCO/CL, and HA-CD@MOF NPs also represent a promising Frontier in breast cancer therapy by leveraging copper’s unique properties for targeted treatment strategies (Table 3) (Chang et al., 2024; Du et al., 2024; Liu et al., 2024; Zheng et al., 2024; Zhou J. et al., 2023; Zhu G. et al., 2024). Additional studies underscore the potential of novel cuproptosis-based nanotherapeutics in breast cancer. M@HMnO2-DP selectively targets tumor cells, delivering DSF to induce cuproptosis independently of external copper sources while disrupting glycolytic pathways and interfering with Fe–S protein synthesis (Zhu J. et al., 2024). Similarly, PCM nano-inducers enhance proteotoxic stress through cuproptosis, leading to the release of mitochondrial DNA that activates the cGAS-STING pathway, thereby initiating a robust immune response that significantly inhibits tumor progression and metastasis (Yu et al., 2024). A novel strategy involving the co-delivery of Cu and erastin in cancer cells has been developed to achieve a synergistic effect by inducing both cuproptosis and ferroptosis (Li Y. et al., 2024). Copper/erastin (CuP/Er) enhances immunogenic cell death, improves antigen presentation, and upregulates PD-L1, promoting T cell proliferation and infiltration. When combined with immune checkpoint inhibitors, it reactivates T cells, leading to effective tumor regression and preventing metastasis in colon adenocarcinoma and triple-negative breast cancer models (Li Y. et al., 2024). This approach underscores the potential of combining multiple cell death pathways to amplify the efficacy of cancer immunotherapies. Expanding on this approach, Huang et al. developed a poly (amidoamine) dendrimer modified with p-carboxybenzenesulfonamide, loaded with copper peroxide nanoparticles and combined with iron-tannic acid networks to form the nanocomposite CuO₂@G5-BS/TF (Huang et al., 2024). This nanocomposite targeted 4T1 tumor cells, facilitating MRI imaging and inducing both ferroptosis and cuproptosis by depleting glutathione and overloading copper and iron. It further neutralized the acidic tumor microenvironment, effectively inhibiting metastasis and offering a dual-functional strategy for TNBC imaging and treatment (Huang et al., 2024). Similarly, the MetaCell system demonstrated the ability to evade immune detection, penetrate breast tumor cells, and promote both cuproptosis and ferroptosis, which resulted in significant anti-tumor effects in vitro and in vivo (Chen K. et al., 2024). Utilizing these therapies, either independently or alongside conventional treatments like chemotherapy and radiotherapy, could greatly enhance breast cancer management. Continued investigation is essential to fully harness their capabilities and improve clinical applications.