HOXD13-mediated immune crosstalk between cancer cells and tumor-associated macrophages drives colorectal cancer progression

Background The complex tumor microenvironment (TME) of colorectal cancer (CRC), composed of diverse cellular components and dynamic interactions, constitutes a major barrier to effective immunotherapy and facilitates disease progression. There is a pressing need to elucidate CRC-intrinsic factors that induce the immunosuppressive TME. Here, we explored the role of homeobox D13 (HOXD13) in shaping the immune microenvironment of CRC and its contribution to immunosuppression. Methods The expression level of HOXD13 was assessed using quantitative real-time PCR, immunoblotting, and immunohistochemistry. The role of HOXD13 in CRC was investigated using orthotopic allograft models and azoxymethane/dextran sulfate sodium-induced spontaneous tumor models in intestine-specific HOXD13 knockout and knock-in mice. The immune landscape of the CRC microenvironment was characterized via flow cytometry and immunofluorescence. Results Our study revealed the upregulation mechanism of HOXD13 in CRC and its functional role in fostering an immunosuppressive TME. HOXD13 was upregulated in CRC, particularly in metastatic cases, and patients exhibiting high HOXD13 expression showed poorer clinical outcomes. Mechanistically, HOXD13 promoted M2-type polarization of tumor-associated macrophages (TAMs) and suppressed CD8 + T cells mediated antitumor immunity by transcriptionally upregulating amphiregulin (AREG) and paired immunoglobulin like type 2 receptor alpha (PILRA) in CRC cells. Concurrently, transforming growth factor beta 1 released from M2-polarized TAMs further augmented HOXD13 expression in CRC cells via activation of the Smad2/3 signaling pathway. This reciprocal interaction formed a self-reinforcing loop that sustained immunosuppression and thereby accelerated tumor progression. Notably, combined inhibition of AREG and programmed cell death ligand 1 effectively disrupted this crosstalk, restored antitumor immunity, and ultimately suppressed CRC progression. Conclusions Our study identified HOXD13 as a pivotal regulator in the establishment of an immunosuppressive TME and suggested that targeting the HOXD13 signaling axis represents a promising strategy to sensitize CRC to immunotherapy.