Tumor-Associated macrophages (TAMs) constitute one of the most prevalent immune cell populations in the TME of numerous solid tumors, including osteosarcoma. Their presence frequently correlates with poor prognosis due to their role in promoting tumor growth, immune evasion, and metastasis. Chemokines and growth factors, largely regulated by NF-κB signaling, are the primary drivers of TAM recruitment to the osteosarcoma microenvironment (40, 41). Among the various chemokines secreted by osteosarcoma cells, including CCL2 (monocyte chemoattractant protein-1, MCP-1) plays a crucial role. It interacts with CCR2 receptor on circulating monocytes, facilitating their recruitment into the tumor microenvironment (42–44). NF-κB functions as a key regulator of CCL2 expression, and its activation in osteosarcoma cells enhances the production of this chemokine, thus enhancing TAM recruitment. Other NF-κB-regulated factors, such as colony-stimulating factors (CSF1 and CSF2), also contribute to monocyte recruitment and their differentiation into TAMs within the tumor niche (45, 46). This process establishes a feedback loop, wherein the presence of TAMs further augments the immunosuppressive and tumor-promoting characteristics of the osteosarcoma TME.

TAMs demonstrates remarkable adaptability, adopting distinct functional states in response to microenvironmental cues. They are typically categorized into two phenotypes: the pro-inflammatory M1 type and the immunosuppressive M2 type. The NF-κB signaling pathway plays a crucial role in this polarization process. ing signals, such as interferon-gamma (IFN-γ) and lipopolysaccharide (LPS), typically activate the classical NF-κB pathway, promoting the development of M1-like macrophages (47, 48). However, in the osteosarcoma TME, TAMs predominantly shift towards the M2 phenotype, influenced by NF-κB-regulated factors, including IL-10, transforming growth factor-beta (TGF-β), and macrophage colony-stimulating factor (M-CSF) (3, 49). These M2 macrophages secrete anti-inflammatory cytokines and express markers like arginase-1 (ARG1), mannose receptor (CD206), and IL-10, which facilitate tissue remodeling, angiogenesis, and tumor immune evasion. M2-polarized TAMs contribute to an immunosuppressive microenvironment by suppressing the activity of cytotoxic T-cells and NK cells, thus hindering effective immune responses against osteosarcoma cells (50). The transition between M1 and M2 states is not irreversible, and NF-κB signaling plays a complex role in regulating this equilibrium. Persistent NF-κB activation within the TME supports the maintenance of the M2 phenotype by enhancing the production of immunosuppressive cytokines and chemokines, thereby augmenting the tumor-promoting functions of TAMs (51, 52).

TAMs exhibit a multifaceted influence on osteosarcoma progression. When TAMs shift to the M2 phenotype, they facilitate immune evasion by secreting immunosuppressive molecules such as IL-10 and TGF-β. These substances inhibit T-cells and NK cell activation and proliferation, creating a localized immune environment that hinders antitumor responses and enables osteosarcoma cells to evade immune-mediated destruction (53). In addition to their immunosuppressive role, TAMs contribute to tumor growth by producing growth factors like VEGF, which promote angiogenesis, ensuring a continuous supply of oxygen and nutrients to support tumor expansion. The NF-κB signaling pathway is crucial in regulating these tumor-promoting activities, as it governs the expression of genes involved in angiogenesis, ECM remodeling, and cell migration (54, 55). Furthermore, TAMs enhance metastasis by establishing a pre-metastatic niche that supports the survival and proliferation of circulating osteosarcoma cells. Through the secretion of chemokines and growth factors, TAMs prepare distant organs, such as the lungs, to support the colonization of metastatic osteosarcoma cells. This process is tightly regulated by NF-κB, which regulates the expression of key metastasis mediators, including MMPs and chemokines such as CCL2 and CCL5 (56, 57).

Chemokines and growth factors secreted by tumor cells attract these cells to the tumor location, with many of these signals regulated by NF-κB signaling. High concentrations of chemokines such as CCL2, CXCL12, and CXCL5 are produced by osteosarcoma cells, which bind to receptors on MDSCs and stimulate their migration into the TME (58, 59). Once inside the TME, MDSCs encounter NF-κB-driven cytokines like IL-6 and GM-CSF, which aid in their survival and proliferation. The continuous recruitment and maintenance of MDSCs in the osteosarcoma microenvironment is ensured by NF-κB activation in both tumor and stromal cells, where they exert potent immunosuppressive effects (60, 61).

T-cell function is potently inhibited by MDSCs, which effectively suppresses the adaptive immune response against osteosarcoma. MDSCs also deplete essential nutrients, such as L-arginine and cysteine, from the microenvironment, further impairing T-cell function (62). The expression of key enzymes like arginase-1 and inducible nitric oxide synthase (iNOS), is controlled by NF-κB signaling. These enzymes play a vital role in the immunosuppressive actions of MDSCs (62).

NF-κB not only facilitates the recruitment of MDSCs but also plays a crucial role in enhancing their proliferation and survival within the osteosarcoma TME. NF-κB activation in response to pro-inflammatory cytokines such as IL-6 and TNF-α results in the upregulation of survival pathways in MDSCs, enabling their persistence in the TME and continued suppression of antitumor immune responses. Moreover, NF-κB signaling augments the expression of genes responsible for MDSC population expansion, thereby maintaining a persistent immunosuppressive environment that promotes tumor progression. Consequently, NF-κB serves as a critical regulator of MDSC-mediated immune suppression in osteosarcoma.

NF-κB signaling impacts various immune cells in the osteosarcoma TME, including NK cells, regulatory T-cells (Tregs), and dendritic cells (DCs), beyond its effects on TAMs and MDSCs. NK cells, as innate immune cells, essential for tumor cell eradication, can be hindered by NF-κB-regulated cytokines and chemokines in the osteosarcoma TME. For instance, TAM-derived TGF-β and IL-10, both regulated by NF-κB, suppress NK cell cytotoxicity, allowing osteosarcoma cells to evade NK cell-mediated immune surveillance (63, 64). NF-κB signaling also promotes the expansion and recruitment of regulatory T-cells (Tregs), which are responsible for maintaining immune tolerance. In the osteosarcoma TME, Treg further suppress cytotoxic T-cells and NK cells, NF-κB-regulated cytokines like IL-10 and TGF-β playing key roles in enhancing Treg expansion and function, thus contributing to the immunosuppressive environment (65, 66). While NF-κB is vital for dendritic cells (DCs) activation and promoting antitumor immunity, chronic NF-κB activation can result in immunosuppressive DCs that ineffectively prime T-cells and instead promote tolerance. The immunosuppressive network within the osteosarcoma TME is intricate and tightly regulated by NF-κB signaling. The interactions among TAMs, MDSCs, Tregs, and other immune cells establishes a microenvironment that facilitates tumor growth, metastasis, and therapy resistance. At the core of this network, NF-κB directs the production of cytokines, chemokines, and various other factors that uphold the immunosuppressive and tumor-supportive characteristics of the TME.

A key feature of NF-κB activation in osteosarcoma is the persistent production of pro-inflammatory cytokines, which maintains a chronic inflammatory environment within the TME. This chronic inflammation not only promotes tumor cell proliferation and survival but also inhibits immune responses, allowing uncontrolled tumor expansion. In osteosarcoma, NF-κB regulates two crucial cytokines: interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α). These cytokines play a vital role in establishing and maintaining the chronic inflammatory conditions observed in the osteosarcoma TME. IL-6, a pro-inflammatory cytokine, serves a dual function by supporting both inflammation and tumor progression. NF-κB activation in osteosarcoma results in elevated IL-6 production, which subsequently activates the Janus kinase/signal transducer and activator of transcription (JAK/STAT3) pathway (67, 68). Furthermore, IL-6 promotes the recruitment of immunosuppressive cells (69, 70). TNF-α, another essential pro-inflammatory cytokine, contributes to the maintenance of chronic inflammation in the osteosarcoma TME. NF-κB regulates TNF-α expression, which subsequently activates NF-κB, creating a positive feedback loop that sustains inflammation. TNF-α aids in the recruitment of TAMs and other immunosuppressive cells, facilitating immune evasion (71, 72). It also enhances osteosarcoma cell survival by activating anti-apoptotic pathways, rendering the cells more resistant to treatment.

NF-κB signaling in osteosarcoma creates a chronic inflammatory conditions that fosters a TME conducive to immune evasion through various mechanisms. Persistent inflammation within the TME promotes the recruitment and activation of immunosuppressive cells, such as TAMs, MDSCs, and regulatory T cells (Tregs). These cells inhibit the function of cytotoxic T lymphocytes (CTLs) and NK cells, which are vital for recognizing and eliminating tumor cells. For instance, TAMs secrete IL-10 and transforming growth factor-beta (TGF-β), both of which inhibit CTL activation, allowing osteosarcoma cells to escape immune detection (73, 74). Pro-inflammatory cytokines like IL-6 and TNF-α stimulate the growth of MDSCs, which potently suppress T-cell functionality. MDSCs hinder the activation of CTLs and NK cells, diminishing the immune system’s ability to generate a robust response against the tumor, thereby facilitating osteosarcoma’s evasion of immune surveillance (71, 75). Additionally, the chronic driven by NF-κB can impair the function of antigen-presenting cells (APCs), including dendritic cells (DCs), which are crucial for presenting tumor antigens to T-cells. This dysfunction undermines the immune system’s capacity to recognize and target osteosarcoma cells, further enabling immune evasion (76, 77).

Immune checkpoint molecules are critical regulators of immune responses, maintaining balanced immune activation and ensuring immune tolerance. However, in cancer, tumor cells frequently exploit these molecules to evade immune surveillance. NF-κB plays a crucial role in regulating the expression of immune checkpoint molecules, especially programmed death-ligand 1 (PD-L1), which acts as a primary mediator of immune evasion in osteosarcoma. In osteosarcoma, the activation of NF-κB leads to increased PD-L1 expression on both tumor cells and immune cells within the TME (78, 79). Pro-inflammatory cytokines such as TNF-α and IL-6, regulated by NF-κB, enhance PD-L1 expression, enabling tumor cells to interact with the programmed death-1 (PD-1) receptor on T-cells. This interaction suppresses T-cell activation and induces T-cell exhaustion, thereby inhibiting the immune response against the tumor. By upregulating PD-L1 expression, NF-κB enables osteosarcoma cells in evading immune detection and elimination (80, 81). The suppression of T-cell function through this immune checkpoint mechanisms is one of the primary ways osteosarcoma evades immune clearance.

Immune evasion in osteosarcoma is largely facilitated by the increased expression of immune checkpoint molecules, particularly PD-L1, which is driven by NF-κB-mediated inflammation. NF-κB also regulates the expression of other immune checkpoint molecules, including cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and T-cell immunoglobulin and mucin domain-3 (TIM-3) (82, 83). These molecules further suppress T-cell activation by inhibiting co-stimulatory signals, thus hindering the immune system’s ability to effectively combat osteosarcoma cells. This immune checkpoint-mediated suppression enables osteosarcoma cells to evade immune surveillance, promoting their continued proliferation and metastasis. The ineffectiveness of T cell-mediated immunity plays a critical role in the progression of osteosarcoma and poses a substantial challenge in the development of effective immunotherapies.

The inflammatory process driven by NF-κB extends beyond initial production of pro-inflammatory cytokines. It also establishes positive feedback loops that perpetuate chronic inflammation and enhance tumor progression. This phenomenon, often referred to as a “cytokine storm,” involves the continuous secretion of cytokines and chemokines, establishing a self-sustaining cycle of inflammation and immune suppression.

A critical feedback mechanism in NF-κB-mediated inflammation involves the interaction between TNF-α and NF-κB itself. When NF-κB is activated, it triggers the production of TNF-α, which further stimulates NF-κB, creating a positive feedback loop that sustains inflammation. This cycle not only aids in osteosarcoma cell survival but also promotes the recruitment of immunosuppressive cells like TAMs and MDSCs, thereby intensifying the immunosuppressive characteristics of the TME. Alongside TNF-α, IL-6 contributes significantly to amplifying NF-κB-driven inflammation by activating the JAK/STAT3 pathway, which can subsequently boost NF-κB signaling (84, 85) This establishes another positive feedback loop that sustains chronic inflammation and supports tumor growth. The continuous activation of these feedback mechanisms ensures that the osteosarcoma TME remains in a state of inflammation, immunosuppression, and favorable conditions for tumor progression.

The cytokine storm triggered by NF-κB-driven inflammation contributes to tumor progression by establishing a TME that enhances tumor cell viability, proliferation, and metastasis. Pro-inflammatory cytokines, such as IL-6 and TNF-α, promote tumor cell survival by activating anti-apoptotic pathways, thereby increasing osteosarcoma cells’ resistance to therapeutic interventions. Moreover, these cytokines stimulate angiogenesis by upregulating vascular endothelial growth factor (VEGF) production, which supports the formation of new blood vessels, which supplies the expanding tumor with essential oxygen and nutrients (86, 87). Additionally, chronic inflammation activates matrix metalloproteinases (MMPs), enzymes that degrade the extracellular matrix, enabling tumor invasion and metastasis. The combined sustained inflammation, immune evasion, and enhanced tumor cell survival makes NF-κB-driven inflammation as a crucial factor in osteosarcoma progression.

A significant obstacle to successful osteosarcoma treatment is chemoresistance, with NF-κB playing a crucial role by promoting cell survival, reducing apoptosis, and enhancing inflammatory response. Several chemotherapeutic agents commonly used in osteosarcoma treatment, including doxorubicin, cisplatin, and methotrexate, initially induce a good response. However, resistance frequently emerges over time, resulting in treatment ineffectiveness.

The primary mechanism of chemotherapy involves triggering DNA damage, oxidative stress, and subsequent apoptosis in rapidly proliferating tumor cells. Nevertheless, osteosarcoma cells often develop mechanisms to evade chemotherapy-induced cellular death, with NF-κB signaling playing a crucial role in this resistance. NF-κB regulates the expression of various genes associated with cell survival, proliferation, and inflammation, enabling tumor cells to resist the cytotoxic effects of chemotherapy.

In osteosarcoma, chemotherapy triggers NF-κB activation through both the canonical (classical) and non-canonical (alternative) pathways. The canonical pathway involves inflammatory cytokines like TNF-α and interleukin-1 (IL-1) activating IκB kinase (IKK), leading to IκB protein phosphorylation and degradation. These IκB proteins typically restrict NF-κB to the cytoplasm, preventing its nuclear entry (88, 89). Once released, NF-κB translocates into the nucleus and initiates transcription of genes that promote cell survival and inhibit apoptosis. In chemoresistance, NF-κB activation upregulates anti-apoptotic proteins, such as Bcl-2, Bcl-xL, and cellular inhibitors of apoptosis proteins (cIAPs). These proteins counteract key components of both intrinsic and extrinsic apoptotic pathways, protecting osteosarcoma cells from chemotherapy-induced apoptosis. In the intrinsic, mitochondria-mediated pathway, elevated Bcl-2 and Bcl-xL levels prevent cytochrome c release, blocking caspase activation, essential for apoptosis. This mechanism enhances the cellular resistance to chemotherapeutic agents, complicating treatment. In the extrinsic pathway, triggered by death receptor signals like Fas, NF-κB-driven upregulation of cIAPs hinders caspase-8 activation, ultimately preventing apoptosis. Furthermore, NF-κB regulates the expression of genes involved in drug resistance, including multidrug resistance protein 1 (MDR1), which encodes P-glycoprotein, a drug efflux pump that reduces intracellular drug concentrations by actively transporting chemotherapeutic agents out of the cell. MDR1 overexpression in osteosarcoma cells diminishes chemotherapy effectiveness by limiting drug accumulation within tumor cells, thus decreasing its cytotoxic effects.

The NF-κB pathway significantly affected by inflammatory cytokines during chemotherapy, especially in osteosarcoma, where the TME is abundant in pro-inflammatory cytokines such as TNF-α, IL-6, and IL-1. These cytokines trigger NF-κB signaling, which contributes to chemoresistance. TNF-α, in particular, is a potent NF-κB activator and has been demonstrated to protect osteosarcoma cells from apoptosis by enhancing the expression of anti-apoptotic proteins like Bcl-2 and cIAPs. Chemotherapy can also stimulate the release of pro-inflammatory cytokines from both tumor and stromal cells, creating a feedback loop that sustains NF-κB activation and enhances survival signaling. Studies indicate that treatment with chemotherapeutic agents such as doxorubicin or cisplatin can induce the release of TNF-α and IL-6. These cytokines subsequently activate NF-κB and increase anti-apoptotic proteins expression, thereby diminishing chemotherapy’s effectiveness and strengthening the cells’ resistance to treatment. This cycle creates a complex environment for eliminating tumor cells, as the reinforced survival signaling undermines the cytotoxic effects of chemotherapy (90, 91). Moreover, the the NF-κB induced anti-apoptotic proteins not only protect tumor cells from chemotherapy-induced death but also enhance their proliferation and resilience under stressful conditions. This enables osteosarcoma cells to evade the cytotoxic effects of chemotherapy and continue to proliferating, leading to the development of chemoresistance and tumor recurrence.

In the treatment of osteosarcoma, radiotherapy is sometimes employed, especially for inoperable tumors or instances of local recurrence. However, tsimilar to chemotherapy, osteosarcoma cells frequently develop resistance to radiotherapy, which reducing its efficacy. NF-κB plays a crucial role in radioresistance, primarily due to its involvement in regulating DNA repair, cell survival, and inflammatory responses to radiation-induced damage. The mechanism of radiation therapy involves causing DNA damage, particularly double-strand breaks, which activate the DNA damage response (DDR). This response triggers various signaling pathways, including the ataxia-telangiectasia mutated (ATM) kinase pathway, which is essential for NF-κB activation following radiation-induced DNA damage. ATM phosphorylates IκB kinase (IKK), resulting in IκB protein degradation and subsequent NF-κB activation. Upon activation, NF-κB translocate to the nucleus and stimulates the transcription of genes involved in DNA repair, cell survival, and inflammation (92, 93). NF-κB contributes primarily by upregulating DNA repair proteins, such as BRCA1, RAD51, and other components of the homologous recombination (HR) pathway. These proteins facilitate the repair of radiation-induced DNA damage, enabling osteosarcoma cells to survive and recover from the radiation therapy effects. By enhancing DNA repair, NF-κB diminishes the cytotoxic impact of radiation, allowing tumor cells to continue proliferating despite treatment. Furthermore, NF-κB activation following radiation therapy induces the expression of anti-apoptotic proteins like Bcl-2 and Bcl-xL, which protect osteosarcoma cells from radiation-induced apoptosis. This inhibition of apoptosis enables tumor cells to withstand the cytotoxic effects of radiation and survive treatment.

Radiotherapy is known to elicit a pro-inflammatory response in the tumor microenvironment, contributing to radioresistance. Irradiated cells release damage-associated molecular patterns (DAMPs) that activate toll-like receptors (TLRs) on immune cells and TAMs. This activation leads to the release of pro-inflammatory cytokines such as TNF-α, IL-6, and IL-1β, which in turn stimulate NF-κB signaling. resulting pro-survival environment supports the survival and proliferation of irradiated tumor cells. The inflammation induced by radiation also promotes the recruitment of immunosuppressive cells, including TAMs, MDSCs, and regulatory T cells (Tregs). These cells enhance radioresistance by inhibiting anti-tumor immune responses. NF-κB plays a crucial role in this process by regulating the expression of chemokines that attract these immunosuppressive cells to the tumor site, creating an immunosuppressive microenvironment that shields osteosarcoma cells from immune-mediated destruction. Furthermore, NF-κB activation following radiation therapy promotes the production of angiogenic factors like vascular endothelial growth factor (VEGF). This leads to the formation of new blood vessels that supply the tumor with essential oxygen and nutrients, not only aiding tumor survival after radiation but also facilitating the growth and metastasis of osteosarcoma cells.

Inflammation in the tumor microenvironment, paradoxically triggered by chemotherapy and radiotherapy, can enhance NF-κB activity and promote therapeutic resistance. This therapy-induced inflammation creates a feedback loop that maintains NF-κB activation and promotes tumor survival, further complicating treatment strategies. The cellular stress and DNA damage caused by these therapies result in the release of pro-inflammatory cytokines and DAMPs from tumor and stromal cells. These inflammatory signals activate the NF-κB pathway, stimulating the expression of genes involved in cell survival, inflammation, and immune evasion. In the context of chemotherapy, the release of DAMP activates toll-like receptors (TLRs) and other pattern recognition receptors (PRRs) on immune cells, leading to the production of pro-inflammatory cytokines such as TNF-α, IL-6, and IL-1β. These cytokines activate NF-κB in both tumor and immune cells, establishing a feedback loop that sustains inflammation and promotes tumor survival (94, 95). Moreover, chemotherapy-induced NF-κB activation increases the expression of anti-apoptotic proteins, DNA repair enzymes, and drug efflux pumps, all of which contribute to chemoresistance. Radiotherapy similarly results in the release of pro-inflammatory cytokines and DAMPs, activating NF-κB through the DNA damage response (DDR) and immune signaling pathways. This NF-κB activation aids in DNA repair, inhibits apoptosis, and amplifies the inflammatory response, all factors that contribute to radioresistance. The recruitment of immune-suppressive cells, including TAMs and MDSCs, further exacerbates resistance by creating an immunosuppressive microenvironment that shields tumor cells from immune-mediated destruction.

The activation of NF-κB in response to inflammation induced by therapy promotes the recruitment and activation of immune-suppressive cells within the tumor microenvironment. TAMs, MDSCs, and regulatory T cells (Tregs) are crucial in promoting therapeutic resistance by inhibiting anti-tumor immune responses and aiding tumor survival. When NF-κB is activated in TAMs, it triggers the secretion of pro-inflammatory cytokines, including IL-10 and TGF-β, which suppress the activity of cytotoxic T cells and NK cells. This creates an immunosuppressive microenvironment that shields tumor cells from immune-mediated destruction and supports their survival following therapy (96, 97). Furthermore, NF-κB also facilitates the recruitment of MDSCs, which hinder T cell activation and proliferation, further reducing the efficacy of the anti-tumor immune response. MDSCs secrete immunosuppressive factors such as arginase-1 and reactive oxygen species (ROS), which impair T cell function and enhance tumor survival. Moreover, NF-κB signaling facilitates the recruitment and expansion of Tregs, which inhibit effector T cell activity and promote immune tolerance towards tumor cells. By suppressing the anti-tumor immune response, Tregs contribute to immune evasion and resistance to therapy in osteosarcoma cells (98–100).

Combining NF-κB inhibitors with conventional therapies like chemotherapy is considered one of the most effective approaches to address therapeutic resistance in osteosarcoma. This strategy, which targets NF-κB signaling, has the potential to enhance the efficacy of chemotherapy, overcome resistance, and reduce tumor progression.

Numerous therapeutic agents have been developed to target the NF-κB pathway either directly or indirectly. These include: IκB kinase (IKK) plays a crucial role in regulating the NF-κB pathway by phosphorylating IκB, which leads to its degradation and subsequent NF-κB activation (101, 102). IKK inhibitors prevent this phosphorylation, thus hindering NF-κB activation. BAY 11-7082 and BMS-345541 are examples of IKK inhibitors that have shown potential in preclinical models by suppressing NF-κB activity and reducing tumor growth. However, the main challenge is to specifically target the IKK complex in tumor cells without impacting normal tissues, as NF-κB is essential for normal immune responses. The proteasome is involved in the degradation of IκB, a necessary step for NF-κB activation. By inhibiting the proteasome, drugs like bortezomib can prevent IκB degradation, thereby preventing NF-κB activation. Bortezomib has received FDA-approval for treating multiple myeloma, and its potential use in osteosarcoma is currently under investigation. Research has demonstrated that bortezomib can make osteosarcoma cells more susceptible to chemotherapy by inhibiting NF-κB-mediated survival pathways. Various natural compounds, including curcumin and resveratrol, have been found to inhibit NF-κB signaling in cancer cells (103, 104). Curcumin, a polyphenol extracted from turmeric, suppresses NF-κB by preventing IκB phosphorylation and subsequent NF-κB nuclear translocation. It has shown anti-inflammatory and anti-tumor properties in osteosarcoma preclinical models, reducing tumor growth and enhancing chemotherapy efficacy. Although natural compounds are less specific than targeted drugs, they offer the benefit of reduced toxicity and could be used as adjuncts to other therapies.

Combining NF-κB inhibitors with chemotherapy offers the potential to enhance the cytotoxic effects of chemotherapeutic agents by sensitizing tumor cells to apoptosis and overcoming chemoresistance. Osteosarcoma cells frequently become resistance to chemotherapy by upregulating NF-κB-mediated survival pathways, including the expression of anti-apoptotic proteins like Bcl-2 and Bcl-xL. Suppressing NF-κB can downregulate these survival pathways, rendering tumor cells more susceptible to chemotherapy-induced apoptosis. Preclinical studies have demonstrated that combining IKK inhibitors or proteasome inhibitors with chemotherapy can result in synergistic effects. For instance, using bortezomib in conjunction with doxorubicin has been shown to significantly reduce tumor growth in osteosarcoma models by promoting apoptosis and suppressing NF-κB activity. Likewise, curcumin has been found to enhance the effectiveness of cisplatin in osteosarcoma by inhibiting NF-κB activation and reducing inflammation. In clinical applications, the primary challenge is determining the optimal timing and dosage of NF-κB inhibitors to maximize their effectiveness while minimizing toxicity. The development of targeted delivery systems, such as nanoparticle-based therapies, could help achieve this goal by delivering NF-κB inhibitors specifically to tumor cells, thus reducing off-target effects.

Cancer treatment has been revolutionized by immune checkpoint inhibitors, such as anti-PD-1 and anti-CTLA-4 therapies, which enable the immune system to target tumor cells. However, these treatments have shown limited efficacy in osteosarcoma, partly due to the immunosuppressive microenvironment driven by NF-κB-mediated inflammation. Modulating NF-κB activity may improve the effectiveness of immune checkpoint inhibitors in osteosarcoma. NF-κB is crucial in regulating the expression of immune checkpoint molecules, including PD-L1, on both tumor cells and immune cells within the TME. The interaction between PD-L1 and the programmed death-1 (PD-1) receptor on T-cells leads to T-cell exhaustion and facilitates immune evasion (105, 106). By suppressing NF-κB, it may be possible to reduce PD-L1 expression, thereby enhancing the anti-tumor immune response and improving the efficacy of immune checkpoint inhibitors.

Research in preclinical models has demonstrated the potential of combining NF-κB inhibitors with immune checkpoint blockade. Specifically, using IKK inhibitors alongside anti-PD-1 therapy has been shown to enhance T-cell activation and reduce tumor growth across various cancer models. This approach could be especially effective in osteosarcoma, where NF-κB-induced inflammation facilitates immune evasion and hinders the anti-tumor immune response. Furthermore, inhibiting NF-κB may enhance the infiltration of cytotoxic T-cells into the TME by reducing the recruitment of immunosuppressive cells like TAMs and MDSCs. This could potentially enhance the effectiveness of immune checkpoint inhibitors by creating a more conducive immune environment for T-cell-mediated tumor elimination.

Although inhibiting NF-κB shows potential for enhancing the effectiveness of immune checkpoint inhibitors, it is essential to recognize NF-κB complex rule in modulating both pro-inflammatory and anti-inflammatory responses. In certain cases, complete suppression of NF-κB could hinder immune response by reducing the production of pro-inflammatory cytokines essential for effective T-cell activation. Consequently, a more refined approach may be required, such as specifically targeting particular NF-κB subunits or signaling pathways involved in tumor promotion while preserving the broader immune response. Current studies have concentrated on elucidating the distinct roles of the canonical and non-canonical NF-κB pathways in tumor immunity. Targeting the non-canonical pathway, which is more closely linked to immune evasion and tumor progression, might offer a more targeted strategy for enhancing immunotherapy while preserving the beneficial immune functions of the canonical NF-κB pathway.

Considering NF-κB therapeutic potential, numerous ongoing preclinical and clinical trials are evaluating the effectiveness of NF-κB inhibitors in treating osteosarcoma. Preclinical studies has shown that these inhibitors can effectively reduce osteosarcoma growth and enhancing the efficacy of other therapies. In particular, experiments using IKK inhibitors and proteasome inhibitors in osteosarcoma models have demonstrated notable reductions in tumor size, decreased metastasis, and enhanced sensitivity to chemotherapy. Additionally, natural compounds such as curcumin have yielded promising results in preclinical models by suppressing NF-κB and inhibiting tumor growth without causing significant toxicity. Some studies have also explored the combining NF-κB inhibitors with immune checkpoint inhibitors, revealing that NF-κB inhibition can enhance the anti-tumor immune response by reducing PD-L1 expression and promoting T-cell infiltration into TME.

Numerous ongoing clinical trials are assessing the safety and effectiveness of NF-κB inhibitors for various cancer, including osteosarcoma. Although most of these studies are in their initial phases, they show potential for the development of novel therapeutic strategies. One such trial is investigating bortezomib, a proteasome inhibitor that suppresses NF-κB activation, in conjunction with chemotherapy for osteosarcoma patients. Preliminary findings indicate that bortezomib may improve chemotherapy effectiveness and reduce tumor size in certain patients (107, 108). Clinical trials are examining the use of IKK inhibitors combined with other therapies. These early stage studies aim to identify the optimal dosing and combination strategies to maximize the therapeutic advantages of NF-κB inhibition. Ongoing clinical studies is also evaluating the use of natural compounds like curcumin and resveratrol in cancer therapy. These investigations seek to determine the safety and efficacy of these compounds in combination with conventional therapies.