MAL2 drives hepatocellular carcinoma progression by recruiting regulatory T cells via CCL22 and inducing the immunosuppressive microenvironment

Hepatocellular carcinoma (HCC) remains a leading cause of cancer-related mortality worldwide, necessitating the identification of novel therapeutic targets. The transmembrane protein MAL2 has been implicated in various cancers, but its functional role and mechanistic underpinnings in HCC are not fully understood. To comprehensively understand its role in HCC, we analyze public single-cell RNA sequencing (scRNA-seq) data and find that MAL2 is significantly enriched in malignant HCC cells. In vitro, MAL2 is stably knocked down by shRNA in Hep-3B and HCC-LM3 cell lines, and functional experiments including colony formation, EdU, transwell, and wound healing assays demonstrate that MAL2 depletion markedly suppresses proliferation, invasion, and migration of HCC cell lines. In vivo, a subcutaneous tumor model using H22 cells reveals that MAL2 knockdown inhibits tumor growth, accompanied by reduced Ki-67 level and increased apoptosis. Further analysis via mass cytometry indicates that MAL2 downregulation reshapes the immune microenvironment, notably reducing CD4⁺ T cells, Tregs, CD8⁺ T cells, and exhaustion markers (PD-L1, PD1, and TIGIT) while increasing B cells and myeloid-derived suppressor cells (MDSCs). Mechanistically, ELISA and immunofluorescence staining validate that MAL2 knockdown impairs the secretion of CCL22, a chemokine known for recruiting Tregs, leading to reduced Treg recruitment and decreased production of the immunosuppressive cytokines IL-10 and TGF-β. In conclusion, MAL2 drives HCC progression by promoting tumor cell proliferation, invasion, and immunosuppression through CCL22-mediated Treg recruitment, positioning MAL2 as a promising therapeutic target to counteract tumor growth and remodel the immunosuppressive microenvironment in HCC.