Macrophages are innate immune cells of bone marrow and embryonic origin that phagocytose foreign substances or their own components and present them to T cells to activate adaptive immune responses. In addition, macrophages also participate in tissue homeostasis, repair and remodeling by expressing a variety of receptors, cytokines, chemokines, and protein hydrolases (19).

Depending on the tissue-specific microenvironmental signals macrophages acquire different phenotypes, mainly including M1 phenotype (classical activation) and M2 phenotype (alternative activation) (20, 21). M1 macrophages can be activated by bacterial lipopolysaccharide (LPS) and type 1 helper T (Th1) cytokines such as interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α), releasing pro-inflammatory cytokines e.g., interleukin(IL)-1β, IL-6, IL-12, and TNF-α, as well as chemokines e.g., C-X-C Motif Chemokine Ligand (CXCL) 9 and CXCL10, and it is capable of presenting antigens via MHC class II molecules (20, 22). M1 macrophage surface markers mainly include CD80, CD86 and CD16/32. M1 macrophages are often considered to have proinflammatory, antitumor, and adaptive immune activation capabilities (23, 24).

M2 macrophages can be activated by Th2-type cytokines IL-4 and IL-13, producing anti-inflammatory factors such as IL-10 and Transforming growth factor beta (TGF-β), as well as chemokines e.g., C-C Motif Chemokine Ligand (CCL)1, CCL17, CCL18, CCL22, and CCL24, with surface markers CD163, CD206, and CD209 (25). M2 macrophages have the function of promoting the resolution of inflammation and participate in tissue repair through angiogenesis at the later stages of inflammation (26–28). Polarized M2 macrophages are divided into M2a, M2b, M2c and M2d subpopulations. The characteristics of the different subtypes of M2 macrophages are listed in Table 1 . M2a and M2b types are involved in immune regulation by promoting the Th2 cell response, while the M2c type is associated with immune response suppression and tissue remodeling (43). The M2d type is activated mainly by tumor cells, tumor-associated factors, or chemotherapeutic agents, and is sometimes referred to as TAMs. This type of macrophage has immunosuppressive and tumor-promoting functions (44, 45) and specifically expresses IL-10. and vascular endothelial growth factor (VEGF) to participate in tumor progression and angiogenesis (44, 46) ( Figure 1A ).

TME serves as the internal environment in which tumor cells are produced and live and regulates tumor initiation and progression. It consists of non-cancerous cells (a variety of immune cells, cancer-associated fibroblasts, endothelial cells), as well as non-cellular components (cytokines, chemokines, proteins, extracellular vesicles, etc.) (47), and the network formed by these elements builds the tumor-promoting environment (48, 49). Monocytes in the peripheral blood are recruited into the highly structured TME and differentiate into TAMs under the influence of chemokines secreted by tumors, such as colony stimulating factor 1 (CSF-1), CCL2, and CCL5 (50, 51). Significant macrophage accumulation has been found in both tumor mouse models and tumor patient tissue samples (46, 52).

TAMs polarization is usually influenced by complex environmental factors in the TME, such as hypoxia, low pH and variable extracellular matrix (ECM) composition (53, 54). In fact, in the early stage of tumor, the immune system promotes macrophages and T cells to clear tumor cells to play anti-tumor and pro-immune response roles (55), and the majority of infiltrating macrophages at this stage are of the M1 phenotype and secrete pro-inflammatory factors (56). For example, granulocyte colony-stimulating factor (G-CSF) polarizes macrophages to a pro-inflammatory phenotype by promoting IL-10 production and reducing IL-12 in colon cancer TME (57). However, as the tumor progresses and the tumor cells continue to interact with the TME, most TAMs are “educated” to become “bad” macrophages that promote tumor growth and metastasis, and then the TAMs take on a predominantly M2 phenotype, creating an immunosuppressive environment and mediating the Th2 immune response (58). Although the M1/M2 polarization model offers a foundational framework for classifying macrophages, it falls short in capturing the phenotypic diversity and plasticity of TAMs. In recent years, researchers have employed surface markers such as F4/80⁺CD68⁺ and F4/80⁺CD206⁺ to delineate distinct TAM subsets (59). Complementing this approach, clustering analyses derived from single-cell RNA sequencing have identified four novel TAM subpopulations across various solid tumors: FCN1⁺, SPP1⁺, C1Q⁺, and CCL18⁺ macrophages. (60, 61). These advancements contribute to a more nuanced understanding of TAM lineage hierarchies and their functional heterogeneity within the tumor microenvironment. TAMs as one of the abundantly infiltrating immune cells in TME, affect tumor angiogenesis and lymphangiogenesis, tumor cell immune escape, immune regulation, and tumor invasion and metastasis (50, 62) ( Figure 1A ).

The inflammatory micro-environment involved and mediated by TAMs is closely related to the occurrence and development of colon cancer (65). Activation of cytokines and chemokines produced by chronic inflammation of tissues, as well as transcription factors such as nuclear factor kappa-B (NF-κB), signal transducer and activator of transcription 3 (STAT3), hypoxia-inducible factor 1α (HIF1α), promotes macrophage recruitment and initiates macrophage host responses (66–68).Macrophages subsequently produce inflammatory mediators (IL-6, TNF, IFN-γ), growth factors such as epidermal growth factor (EGF) and WNTs, proteases, reactive oxygen species (ROS), as well as nitric oxide (NO) that may activate proto-oncogenes to promote tissue carcinogenesis (69–71). Not only that, these substances produced by TAMs can also promote colon cancer growth. Studies have found that CCL2, IL-1α and IL-6 secreted by TAMs can promote the proliferation of colon cancer cells (72), and the release of the matrix metalloproteinase (MMP) 1 accelerates the transition of the tumor cell cycle from the G0/G1 phase to the S phase and G2/M phase (73).CSF1 is an important cytokine involved in macrophage proliferation and differentiation, and CSF1 produced by colon cancer cells contributes to the recruitment and infiltration of TAMs. In turn, IL-8 produced by TAMs can activate the PKC pathway on which CSF1 production depends (74).

Epithelial-mesenchymal transition (EMT) is an important development process that is activated during tumor cell migration and invasion (75). Activation of EMT prompts colon tumor cells to lose cell polarity and intercellular adhesion, and to acquire a mesenchymal appearance and greater infiltration and migration capabilities (76). In TME, several EMT-associated transcription factors (ZEB, SNAIL, and TWIST) synergize with signaling pathways in tumor cells (77–79) to induce EMT in response to stimulation by TGF-β, WNT, NOTCH, hypoxia (80–82), etc. TAMs have been demonstrated to have a key role in EMT in colon cancer. M2 macrophages overexpress MMP2 and MMP9, which can induce EMT (83). TGF-β is an important factor in EMT (84). M2 macrophages secrete a large amount of TGF-β, which promotes the expression of mesenchymal marker proteins (Vimentin) and reduces the expression of epithelial marker proteins (E-cadherin) during EMT in colon cancer cells (85). In addition, Wei et al. reported that TAM-derived IL-6 induced the EMT program by regulating the JAK2/STAT3/miR-506-3p/FoxQ1 axis to promote colon cancer cell invasion and migration (86). In colorectal cancer, the number of infiltrating TAMs is positively correlated with the expression of the activating transcription factor SANIL in cancer cells (76). TAMs also promote tumor invasion by up-regulating the expression of S100A8 and S100A9 in cancer cells (87).

Structural support for tumor development is provided by the ECM, including its main components collagen, glycoproteins and proteoglycans (88–90). Afik et al. found that in an orthotopic colorectal cancer model, TAMs promote the deposition, cross-linking, and linearization of collagen fibers to remodel tumor ECM composition and structure and promote tumor development (91).

Colon cancer cells can also activate matrix degradation-related signals to induce TAMs to produce tissue proteases, MMPs and serine proteases, etc., to promote ECM degradation and accelerate the invasion and migration of colon cancer cells (76, 88) ( Figure 1B ).

Tumor growth and metastasis require increased intratumoral blood supply, which is usually triggered by tumor hypoxia (92). TAMs infiltrating the TME of colon tumors express HIF1α as an “angiogenic switch”, and respond to hypoxia signals by producing pro-angiogenic cytokines and growth factors, such as Angiopoietin-2 (Ang-2), VEGF, IL-8, CXCL1, and Fibroblast growth factor 2 (FGF-2), to induce endothelial cell recruitment, proliferation, and maturation, forming new blood vessels to promote tumor growth (67, 93, 94). GPR35 on macrophages in colon cancer promotes new angiogenesis and increases MMPs activity through Na/K-ATPase-dependent ion pumps and Src activation (94). Additionally, multiple studies have shown that the number of TAMs in colon cancer correlates with vascular density and the number of lymphatic vessels (95–97). Macrophages on blood vessels emit attractive signals that assist colon cancer cells in migrating along collagen fibers toward the vessels, enabling their escape into the bloodstream. TAMs can also activate the EGFC/VEGFR3 axis, which supports primary colorectal cancer cells growth and metastasis by shaping the lymphatic vessels and providing a pathway for tumor cells to invade the lymphatic system (98) ( Figure 1C ).

During colon cancer progression, the body’s anti-tumor immunity is suppressed, and tumor cells effectively evade anti-tumor immunity by deriving a tumor-immunosuppressive microenvironment, which involves inducing deletion or functional impairment of tumor-reactive T-cells (99) and recruiting immunosuppressive cell populations such as regulatory T-cells (Tregs) and myeloid-derived suppressor cells (MDSCs) (100). TAMs participate in and regulate the tumor immunosuppressive microenvironment by secreting cytokines and altering their phenotype (predominantly M2 macrophages) (101).

TAMs exert immunosuppressive functions through the secretion of inhibitory factors, such as IL-10, TGF-β, and Indoleamine 2,3-Dioxygenase 1 (IDO1) (68, 102), some enzymes, such as COX2, Arginase 1 (ARG1), Inducible nitric oxide synthase (INOS), and MMPs (101), as well as the release of chemokines (e.g., CCL2, CCL3, CCL4, CCL5, and CCL20) (68, 103, 104). The release of these factors not only directly inhibits the activity of T cells (105), but also promotes the recruitment of Tregs and MDSCs in the TME. For example, TAMs promote the aggregation of CCR6+ Treg cells by secreting CCL20 (106), and secreted CCL5 inhibits the killing of HT29 cells by T cells by stabilizing PD-L1, which in turn promotes immune escape (107). In tissue samples from colon cancer patients, the number of Treg cells and macrophages was significantly higher in cancerous tissues than in precancerous tissues (108). The infiltration of a large number of M2 macrophages is associated with poor prognosis, while the infiltration of CD8+ T cells is associated with improved patient survival (109). It was found that cytotoxic T cell responses could be enhanced to prevent colon cancer metastasis by inhibiting TGF-β produced by M2 macrophages (110). In addition, infiltration of high-density CXCR6⁺ TAMs promote the overexpression of IL-6, which would inhibit the activation of CD8⁺ T cells, thus contributing to immunosuppression (111). Ding et al. demonstrated that targeted inhibition of MDSCs could improve the immune microenvironment of colon cancer, not only promoting the maturation of dendritic cells and tumor infiltration of CD8⁺ T cells, but also reducing the number of Tregs and M2 macrophages (112) ( Figure 1D ).

Macrophages, as “professional” phagocytes in the innate immune system, play the role of scavengers. However, to evade clearance, tumor cells usually overexpress anti-phagocytic membrane proteins with “don’t eat me” signals, such as CD47, CD24, MHC-I, and PD-L1. These antiphagocytic proteins may interact with receptors on macrophages (e.g., SIRPα, Siglec-10, LILRB1, and PD-1) to evade phagocytosis. The anti-phagocytic signals generated by these binding are known as “Phagocytosis checkpoints”. Targeting phagocytosis checkpoints such as CD47-SIRPα, CD24-Siglec-10, MHC-LILRB1, PD1-PDL1 and thereby modulating immune escape in colon cancer cells has also been demonstrated.

Studies have found that using blocking antibodies targeting CD47 overexpressed on colon cancer cells and SIRPα on TAMs can inhibit the migration of colon cancer cells (113–115). In addition, phagocytic activity of macrophages was enhanced after anti-SIRPα antibody treatment (116). Interestingly, under hypoxic conditions, TAMs showed decreased SIRPα expression accompanied by increased phagocytic activity, whereas colon cancer cells showed elevated expression of CD47 and exhibited greater invasiveness (117). Therefore, it can be hypothesized that the regulation of the CD47-SIRPα axis in colon cancer may be affected by hypoxia.

CD24 serves as a critical “don’t eat me” signal molecule expressed by tumor cells. Several studies have indicated that its overexpression in colorectal cancer cells is associated with early-stage tumor metastasis (118). In colon cancer xenograft mouse models, treatment with anti-CD24 antibodies effectively suppressed the tumor growth (119, 120). Interestingly, Nersisyan et al. reported that reduced CD24 expression or gene loss in colon cancer patients was linked to shorter overall survival (121). These findings suggest that CD24 may function as a stage-specific driver during colorectal tumorigenesis—upregulated in early disease and potentially regulated later by shifts in immune cell activity. Zhao et al. further found a negative correlation between CD24 expression and multiple immune-related pathways, including TNF-α, NF-κB, and IFN-γ signaling (122). Siglec-10 has also been identified as an early driver gene in colorectal malignancies, with mutations observed in both multiple colonic adenomas and colorectal tumors (123). Single-cell RNA sequencing data revealed an enrichment of FOLR2⁺ LYVE1⁺ macrophages in KRAS/TP53 double-mutant colon cancer, where tumor cells appear to engage in immunosuppressive crosstalk with macrophages via the CD24–Siglec-10 axis. (124). Blocking the CD24–Siglec-10 anti-phagocytic axis effectively activates macrophage-mediated phagocytosis in the MC38 colon cancer model (125).

In colorectal cancer DLD1 cells, MHC-I expression suppresses macrophage-mediated phagocytosis and promotes immune evasion, primarily through its interaction with LILRB1 on TAMs. In vivo studies have shown that CRISPR-mediated knockout of MHC-I molecules in tumor cells suppresses tumor growth in a macrophage-dependent manner (126). However, in tumor tissues from patients with colon cancer liver metastases, high expression of MHC-I (β2m) on tumor cells has been associated with improved overall survival and increased T cell infiltration (126). The dual role of MHC-I in tumor immune evasion may stem from its capacity to engage both innate and adaptive immune responses. When functioning as an antigen-presenting molecule to cytotoxic T lymphocytes, MHC-I may no longer interact effectively with LILRB1. Additionally, some studies have reported that reduced MHC expression on tumor cell surfaces impairs antigen presentation, which may, in turn, enhance macrophage-mediated phagocytosis (127).

PD-1/PD-L1 inhibitors have been shown to effectively reverse T cell immune tolerance. In addition to T cells, PD-1 is also expressed on other immune cells, including macrophages, B cells, NK cells, and dendritic cells. Notably, increasing attention has been directed toward the functional role of PD-1/PD-L1 signaling in TAMs (128). Studies have reported that colon cancers with MSI-H tend to exhibit elevated PD-L1 expression, and that PD-1 levels on TAMs increase as the disease progresses (14, 129). PD-1 expression on macrophages has been implicated in promoting polarization toward the immunosuppressive M2 phenotype. In murine models of colorectal cancer, PD-1 blockade has been shown to reduce the infiltration of M2 macrophages within the TME (130). The PD-1/PD-L1 axis is considered part of an anti-phagocytic signaling pathway. In both colon cancer patients and mouse models, high PD-1 expression on TAMs has been associated with reduced phagocytic activity against tumor cells. Disruption of this axis can induce M1 polarization of macrophages and promote CD8⁺ T cell activation, thereby enhancing antitumor immunity (14). ( Figure 1D ).

In pro-inflammatory or anti-inflammatory TME, TAMs exhibit notable metabolic plasticity. They comprehensively reprogram their energy sources, metabolic pathways, and metabolites to adapt to tumor progression. In colon cancer, tumor cells undergoing rapid proliferation produce lactate through the Warburg effect. The resulting acidic environment facilitates TAM recruitment and induces their immunosuppressive functions.

Similar to tumor cells, M1 macrophages rely on aerobic glycolysis and the pentose phosphate pathway (PPP), with upregulation of HIF-1α-related signaling, promoting the production of lactate and succinate (131). In contrast, M2 macrophages exhibit lower glucose consumption and primarily depend on fatty acid oxidation (FAO) and oxidative phosphorylation (OXPHOS) for energy supply. They express high levels of CD36, facilitating fatty acid uptake and β-oxidation. Additionally, FAO-induced mitochondrial stress and elevated ROS levels contribute to M2 polarization (132). It has been shown that the STING agonist GB2 can induce metabolic reprogramming of TAMs in colorectal cancer by upregulating the glycolysis–ROS–HIF-1α axis and downregulating OXPHOS, thereby promoting M1 polarization and enhancing phagocytic activity (133).

Increased glucose uptake leads to the accumulation of lactate in the TME. Zhang et al. were the first to reveal the role of histone lysine lactylation in the modification of macrophages, demonstrating that the level of lysine lactylation is positively correlated with intracellular lactate concentration (54). In colon cancer, elevated lactate levels promote M2 polarization and the secretion of signaling molecules that facilitate tumor progression. (76, 133). For example, lactate in the tumor microenvironment epigenetically upregulates the expression of VSIG4 in macrophages, which subsequently activates the JAK2/STAT3 pathway, enhances fatty acid oxidation and PPAR-γ expression, and drives polarization toward an immunosuppressive M2 phenotype (134).

In terms of amino acid metabolism, M1 macrophages primarily utilize arginine metabolism by upregulating iNOS to produce citrulline and NO, thereby enhancing antimicrobial and antitumor activity. In contrast, M2 macrophages upregulate ARG1, converting arginine into ornithine and polyamines, which contribute to immunosuppression (16). Increased expression of ARG1 has been identified as a key factor in rapid tumor growth and progression (16). Additionally, M2 macrophages metabolize tryptophan via IDO1 to generate kynurenine, which suppresses T cell function and promotes immune tolerance. It has been shown that inhibiting ARG1 while activating iNOS can effectively increase the number of M1 macrophages and suppress colon tumor growth (135).

Autocrine and paracrine signaling mediated by cytokines and chemokines plays a pivotal role in the communication between tumor cells and TAMs. Both tumor cells and TAMs are capable of internalizing exosomes secreted by one another, thereby releasing their endosomal contents. This exchange contributes to the regulation of macrophage polarization and influences key tumor behaviors, including invasion, metastasis, and immune evasion ( Table 2 ) ( Figure 2 ).

In colon cancer, exosomes released by TAMs and colon cancer cells jointly contribute to the regulation of tumor immunity. Specifically, colon cancer cells can secrete exosomes containing various non-coding RNAs—including microRNAs (miRNAs), long non-coding RNAs, and circular RNAs, which influence TAM polarization. For instance, exosomal miR-1246 and miR-92a-3p derived from tumor cells have been shown to activate STAT3 and ERK signaling pathways in TAMs, promoting their polarization toward an immunosuppressive M2 phenotype (137, 149). Similarly, circ_0020095 facilitates tumor cell invasion and migration by downregulating IRAK1 expression and suppressing M1 polarization (139). In addition to RNA cargo, tumor-derived exosomes can also transport specific proteins that modulate the immune response. HSP90B1, delivered via exosomes from colorectal cancer cells, has been associated with poor prognosis in advanced colorectal cancer and contributes to liver metastasis by promoting the conversion of M1 to M2 macrophages (141). Notably, treatment targeting HSP70-positive exosomes produced by colorectal cancer cells has been reported to enhance antitumor immune responses, suggesting that TAMs possess functional plasticity (142).

On the other hand, TAMs can also influence tumor progression through the transfer of RNA and protein molecules encapsulated within exosomes. For example, M2 macrophages have been shown to promote colon cancer cell proliferation by delivering ferritin heavy chain (FTH1) protein via exosomes (148). Additionally, TAM-derived exosomes exhibit high levels of miR-21-5p and miR-155-5p, which target and suppress the expression of BRG1 in tumor cells, thereby enhancing their malignant properties and facilitating immune evasion (143).

Evidence suggests that chronic low-grade inflammation due to gut microbial dysbiosis as well as impaired intestinal barriers are important factors driving colon cancer development (150–152). Infiltrating bacterial products can construct an immunosuppressive TME by shaping TAMs (153). Fewer macrophages were found in the intestinal wall of germ-free mice compared to SPF mice (154, 155). Enrichment of Fusobacterium nucleatum, Bacteroides fragilis, Escherichia coli, and Enterococcus faecalis has been observed in the feces or tumor tissues of colorectal cancer patients (156–159). The establishment of chronic inflammation promotes colorectal cancer development. In APCmin/+ mice, Fusobacterium nucleatum facilitates the recruitment and infiltration of specific myeloid cell subsets into tumor tissue, producing NF-kB-related pro-inflammatory characteristics (160, 161). In a mouse model infected with Citrobacter rodentium, macrophage-derived ornithine decarboxylase promotes M1 macrophages activation, leading to increased mucosal inflammation in the colon (162). Gut microbes also promote colon carcinogenesis by modulating macrophage immunoreactivity. In Fusobacterium nucleatum-fed mouse models with intestinal tumors, M2-like macrophage accumulation has been observed within tumor tissues, showing significant suppressive activity against CD4+ T cells (160). Additionally, bacterial products such as muramyl peptides activate NOD1, maintaining ARG-1 overexpression and promoting colorectal tumor formation by modulating the immunosuppressive activity of MDSCs and TAMs (153). However, most current studies have focused on the crosstalk between tumorigenic bacteria and TAMs, and the role of some beneficial bacterial species is easily overlooked. For example, Akkermansia muciniphila, a probiotic with strong adhesion to the intestinal epithelial cell surface, can mediate M1 macrophages accumulation in a TLR2/NLRP3-dependent manner to inhibit colorectal tumorigenesis (163) ( Figure 1E ).

Studies have confirmed that botanical compounds exhibit significant pharmacological and biological activities in the treatment of colon cancer (164, 165). Among these, polysaccharides, polyphenols, saponins, quinones, and terpenoids have been found to exert anti-tumor effects by modulating TAMs. The specific mechanisms of action are summarized in the table below ( Table 3 ).

Natural compounds face limitations in clinical applications, such as unstable efficacy, poor solubility, and challenges in standardization. To overcome these issues, synthetic modifications can be employed to create novel drug formulations by knocking out or altering certain unstable structures of the compounds. We summarize the role and mechanisms of existing synthetic formulations based on natural products targeting TAMs in colon cancer ( Table 4 ).

Aspirin, derived from salicylic acid, is a classic non-steroidal anti-inflammatory drug. Long-term low-dose administration of aspirin (25 mg/kg daily in healthy mice, equivalent to 100 mg in human subjects) significantly reduces macrophage infiltration in colon tumors, shrinks tumor size, and decreases the formation of prostaglandin E2 (PGE2) in the colon (193).Modified mannose β-cyclodextrin (Man-MβCD) can be recognized by mannose receptors (MR) on TAMs, enhancing the cytotoxic activity of M2 macrophages while promoting tumor cell autophagy (196).Plinabulin, a microtubule inhibitor synthesized from a natural product isolated from marine Fusarium fungi through structural optimization, is undergoing global Phase III clinical trials for tumor treatment. In vivo studies have shown that Plinabulin (7 mg/kg) induces M1 polarization in macrophages through the JNK signaling pathway, effectively inhibiting tumor growth in MC38 colon cancer-bearing mice (195).The synthetic retinoid derivative fenretinide demonstrates advantages in chemoprevention, significantly reducing tumor occurrence in APCmin/+ mice by inhibiting STAT6 signaling and decreasing M2 macrophage-driven angiogenesis in tumor tissues (194).Blocking CSF-1/CSF-1R signaling to regulate TAM polarization is a promising therapeutic approach. A synthesized compound 21 from a series of (Z)-1-(3-((1H-pyrrol-2-yl)methylene)-2-oxoindolin-6-yl)-3-(isoxazol-3-yl)urea derivatives exhibits excellent CSF-1R inhibitory activity (IC50 = 2.1nM), promoting M1 macrophage infiltration and enhancing anti-tumor immune responses (197).

While synthetic formulations effectively improve the efficacy and stability of natural products, the high research and development costs, along with complex clinical trial processes, remain significant obstacles to their widespread application. Improving the production methods of synthetic formulations, such as utilizing advanced techniques like computer-aided drug design, can aid in the development of synthetic formulations based on natural products.

Currently, immune checkpoint inhibitors (ICIs, immune checkpoint inhibitors) are working in microsatellite instable/mismatch repair deficient patients that account for about 5-10% of CRC cases. Optimized combination therapy strategies could expand the use of anti-PD-1/PD-L1-based immunotherapy in colon cancer. Although current immunotherapies are mostly centered on T cells, more and more reports support that the effector function of innate immunity is also important for cancer treatment ( Table 4 ).

Several studies have explored the synergistic effects of natural products combined with anti-PD-1 (aPD-1) immunotherapy in colon cancer, primarily through the inhibition of TAMs’ M2 polarization and the activation of T-cell immune responses. For example, Astragaloside IV (AS-IV) from Astragalus membranaceus, sesquiterpene lactones from Arctium lappa, and the natural Chinese yam polysaccharide (CYP) have been shown to shift TAMs from the immune-suppressive M2 phenotype to the anti-tumor M1 phenotype. When used in combination with aPD-1, these natural products enhance the tumor immune response, increase the infiltration of CD8+ T cells, and inhibit tumor growth (184, 198, 200). Additionally, CYP has been found to effectively regulate the disruption of gut microbiota and metabolic products associated with aPD-1 treatment (200).

Another promising strategy involves combining natural compounds with conventional chemotherapy agents such as 5-FU. While 5-FU is a cornerstone in the treatment of colon cancer, its efficacy is limited due to the development of chemoresistance. 7S,15R-Dihydroxy-16S,17S-Epoxy-Docosapentaenoic Acid (diHEP-DPA), a DHA derivative, has been shown to overcome 5-FU resistance when used in combination, inhibiting TAM infiltration, reducing the accumulation of cancer stem cells (CSCs), and suppressing EMT (201, 202). Similarly, Ovatodiolide enhances anti-tumor effects when combined with 5-FU by inhibiting the YAP1 oncogenic pathway and preventing M2 TAM polarization (203).

The combination of natural products with existing cancer therapies (such as ICIs and chemotherapy) offers multiple advantages, particularly in enhancing current therapeutic efficacy, overcoming resistance, and reducing side effects. However, current research has primarily focused on the combination of natural products with anti-PD-1 immunotherapy, with limited studies on the use of other immunotherapies in combination with natural products for colon cancer treatment. Future research should explore the synergistic effects of different immune checkpoint inhibitors with natural products to provide more treatment options for clinical practice.

Nanomedicines have shown great potential in cancer treatment and have become a promising strategy to overcome the pharmacokinetic limitations of natural compounds. Despite substantial evidence supporting the superior antitumor effects of natural products, their clinical application remains limited due to issues such as poor solubility, low bioavailability, and insufficient systemic stability. The rapid development of functional nanomaterials has enabled nanomedicines to effectively address these challenges by facilitating accurate drug release, enhancing tumor penetration, and improving retention through the enhanced permeability and retention (EPR) effect, all while reducing toxicity and side effects (204). Common carriers include biomimetic delivery platforms (e.g., erythrocyte membranes, leukocyte membranes, stem cell membranes, and extracellular vesicles), liposomes, polymeric particles, and inorganic nanoparticles. Preclinical studies suggest that TAM-targeting nanomedicines exhibit good safety, enhanced stability, and improved anticancer performance in colon cancer treatment ( Table 5 ).

Traditional Chinese medicines effectively inhibit the development of colon cancer through various pathways, such as enhancing immune response and inhibiting tumor proliferation and metastasis. Garcinia yunnanensis, a traditional Chinese medicine, has anticancer and anti-inflammatory effects, and after Garcinia yunnanensis treatment of APCmin/+ colon cancer model mice, JNK, STAT3 and ERK signaling were inhibited, M2 macrophage infiltration in the TME was reduced, and the size of tumors was reduced (219). Yi-Yi-Fu-Zi-Bai-Jiang-San (YYFZBJS) is a commonly used traditional Chinese medicine formula for treating inflammatory diseases. YYFZBJS can alter the pro-tumor effects of M2 macrophages by inhibiting inflammation-related signaling pathways in colon cancer and delay the development of the disease by reshaping the gut microbiota (220). Si-Jun-Zi Decoction (SJZ) is a well-known Chinese herbal formula that can regulate human immunity. After 3 weeks of treatment with full dose (45 g/kg) of modified SJZ in mice with colorectal cancer, the expression level of GM-CSF in plasma and the number of splenic macrophages were significantly increased, and the nude mice had better body defenses and colorectal cancer survival rate, and the modified SJZ also reduced the hepatic metastasis of colorectal cancer by activating the innate immunity (221).

The development of malignant tumors can have a deleterious effect on the patient’s mood and even accelerate tumor metastasis, and some traditional Chinese medicines can slow down this process. Xiao-Yao-San, is widely used clinically for the relief of symptoms associated with depression. Treatment of colorectal model mice with Xiao-Yao-San reduced the recruitment of M2 macrophages and MDSCs, and inhibited the expression of TGF-β, IL-6, MMP-9 and VEGF. Not only that, Xiao-Yao-San can also effectively inhibit liver metastasis of chronic stress colon tumors (222). Hereby, the natural products, with their excellent activity, safety and novel structures, offer more possibilities for the development of novel anti-colon cancer drugs.

Probiotics are defined by the World Health Organization (WHO) as “active microorganisms that, when ingested in sufficient quantities, are beneficial to the health of the host”. Probiotics stabilize the intestinal barrier and modulate intestinal immunity. Extensive research has shown that the consumption of probiotics (e.g. Lactobacillus plantarum, Lactobacillus acidophilus, and Bacillus subtilis) can alter the distribution of cellular junctional proteins, reduce the absorption of potentially cancer-causing compounds, and improve the poor prognosis of colon cancer (223–226).

lactobacilli, a probiotic used with high frequency in the treatment of diseases. Hradicka et al. found that Lactobacillus has immunomodulatory activity, remodels macrophage polarization, and reduces colon tumor tissue volume and total tumor number (227). Lactobacillus acidophilus lysate in combination with CTLA-4 helps to enhance anti-tumor immune response in colon cancer mice by decreasing Treg and M2 macrophage infiltration, and increasing the number of CD8+ T cells in the TME (228). Saccharomyces cerevisiae (S. cerevisiae) is a conventional yeast used in food products and a probiotic that maintains intestinal homeostasis. Beta-glucan, a major component of the cell wall of S. cerevisiae, inhibits colon tumor activity by suppressing intestinal ecological dysregulation and activating macrophages (229). Loigolactobacillus coryniformis NA-3 induces NO, IL-6, TNF-α, and ROS production in colonic TAMs and significantly inhibits the proliferation of colonic tumor cells (230). Notably, appropriate dosage and sufficient intestinal residence time are crucial for probiotics to exert anticancer immune effects (231). In addition, several studies have confirmed that the use of probiotics can help alleviate gastrointestinal adverse reactions such as diarrhea and nausea caused by chemotherapeutic drugs and improve patients’ treatment tolerance (231–233).

Dietary intervention is an emerging strategy for disease prevention and treatment. A Western diet characterized by high intake of red meat and high fat has been shown to significantly increase the risk of colorectal cancer (234). In contrast, diets rich in dietary fiber have a protective effect on the gut, not only providing an energy source for gut microbes, but also helping to maintain gut homeostasis and barrier integrity. Compared to normal-diet colon cancer model mice, ketogenic diet induces oxidative stress within colon tumors, promotes conversion of M2 macrophages to M1-type, and downregulates MMP expression to inhibit colon tumor progression (235). In addition, some dietary intake can also alleviate colon cancer progression to some extent. Feeding a diet rich in Oleuropein-Rich Leaf Extract to colon cancer model rats abrogated the overexpression of iNOS in rat tumors and inhibited the pro-inflammatory behaviors of macrophages in rats with loaded tumors, suppressing tumor proliferation (190). 3-Hydroxybutyrate (3HB) has various utilities as an oral food supplement, such as energy supply, anti-inflammation, neuroprotection, and can be used to improve alcoholic fatty liver, osteoporosis, and Alzheimer’s disease. Li et al. found that 3HB could regulate colon TME, modulate the proportion of infiltrating macrophages, and reduce the level of MDSCs, as well as inhibit the NF-κB pathway that reduces inflammatory factor release (236). Sea cucumber, a marine animal rich in bioactive molecules, is a dietary nutrient with anti-inflammatory and antibacterial effects. Adding sea cucumber extract Frondanol A5 to the feed fed to APCmin/+mice significantly reduced the volume of colon tumors, increased the phagocytosis efficiency of mouse peritoneal macrophages, and provided prevention for intestinal tumorigenesis (237).