Epigenetic inactivation of COL4A4 orchestrates JAK2/STAT3-driven progression and microenvironment reprogramming in renal cell carcinoma.

BACKGROUND: Renal cell carcinoma (RCC) is a common urinary malignancy that lacks reliable early biomarkers. Although epigenetic silencing of tumor suppressor genes mediated by DNA methylation is common in RCC, the specific role and regulation of the basement membrane component COL4A4 remain unclear. METHODS: Bulk and single-cell RNA sequencing (scRNA-seq), DNA methylation analysis, The Cancer Genome Atlas data and in-house clinical RCC cohorts were integrated to characterize COL4A4 expression, epigenetic regulation, clinical significance, and associations with tumor microenvironment (TME) features. The biological functions of COL4A4 were evaluated using in vitro functional assays and in vivo xenograft models. Mechanistic studies included 5-Aza demethylation treatment and JAK2/STAT3 pathway inhibition. RESULTS: COL4A4 was downregulated in RCC, and its downregulation is associated with promoter hypermethylation, serving as an independent prognostic factor. Functionally, COL4A4 inhibited RCC cell proliferation, migration, and invasion in vitro, and suppressed tumor growth in vivo. Mechanistically, COL4A4 negatively modulated the JAK2/STAT3 signaling pathway. scRNA-seq revealed that COL4A4 was predominantly enriched in epithelial cells. Low COL4A4 expression is associated with altered extracellular matrix-receptor interactions and an immunosuppressive TME. CONCLUSIONS: COL4A4 acts as a methylation-silenced RCC tumor suppressor that negatively modulates JAK2/STAT3 signaling and correlates with TME features, representing a potential epigenetic therapeutic target.