FOXM1-mediated transcriptional activation of CILP2 promotes malignant phenotypes and EMT-associated remodeling in clear cell renal cell carcinoma

Background Clear cell renal cell carcinoma (ccRCC) is the most common histological subtype of renal cancer and remains associated with aggressive progression and poor clinical outcomes. Cartilage intermediate layer protein 2 (CILP2), an extracellular matrix-associated secreted protein, has been implicated in tumor-related processes, but its biological role and regulatory mechanism in ccRCC remain unclear.Methods CILP2 expression and its association with clinical outcomes were evaluated using multiple public datasets and further examined in clinical specimens. Gain- and loss-of-function assays were performed in A498 and 786-O cells to assess the effects of CILP2 on proliferation, migration, invasion, and colony formation. Xenograft experiments were conducted to evaluate tumor growth in vivo. The transcriptional regulation of CILP2 by FOXM1 was examined by ChIP-PCR and dual-luciferase reporter assays. Gene set enrichment analysis, RT-qPCR, western blotting, and immunofluorescence were used to investigate downstream pathways. Associations between CILP2 and the immune microenvironment were also analyzed.Results CILP2 was significantly upregulated in ccRCC and its high expression was associated with advanced clinicopathological features and poor survival. Functionally, CILP2 knockdown suppressed proliferation, migration, invasion, and clonogenicity of ccRCC cells, whereas CILP2 overexpression exerted the opposite effects. In vivo, CILP2 depletion reduced xenograft growth. Mechanistically, FOXM1 directly bound to the CILP2 promoter and positively regulated its transcription. Transcriptomic and experimental analyses indicated that CILP2 promoted an EMT-associated malignant phenotype, accompanied by decreased epithelial markers and increased mesenchymal markers. Exploratory bioinformatic analyses further showed that elevated CILP2 expression was associated with computationally inferred Treg abundance and CAF-related stromal features.Conclusions These findings support CILP2 as a candidate prognostic marker and a contributor to malignant phenotypes in ccRCC. FOXM1-mediated transcriptional regulation of CILP2 is associated with EMT-related remodeling, whereas the observed immune- and stromal-related associations remain exploratory. The clinical utility and therapeutic targetability of the FOXM1/CILP2 axis require validation in larger prospective cohorts and more physiologically relevant models.