CA-125 as a Biomarker in Renal Medullary Carcinoma: Integrated Molecular Profiling, Functional Characterization, and Prospective Clinical Validation [RNA-Seq]

Purpose: Renal medullary carcinoma (RMC) is a highly aggressive malignancy defined by the loss of the SMARCB1 tumor suppressor. It mainly affects young individuals of African descent with sickle cell trait, and it is resistant to conventional therapies used for other renal cell carcinomas. This study aimed to identify potential biomarkers for early detection and disease monitoring of RMC. Experimental Design: Integrated profiling of primary untreated RMC tumor tissues and paired adjacent kidney controls was performed using RNA-sequencing (RNA-seq) and histone Chromatin Immunoprecipitation Sequencing (ChIP-seq). The expression of serum cancer antigen 125 (CA-125), was prospectively evaluated in 47 patients with RMC. Functional studies were conducted in RMC cell lines to assess the effects of SMARCB1 re-expression and MUC16 knockdown. Results: MUC16, encoding for CA-125, was identified as one of the top upregulated genes in RMC tissues, with concomitant enrichment of active histone marks H3K4me3 and H3K27ac at its promoter. Elevated serum CA-125 levels were found in 31 of 47 (66%) RMC patients and correlated significantly with metastatic tumor burden (p = 0.03). SMARCB1 re-expression significantly reduced MUC16 expression in RMC cell lines. Functional studies in RMC cell lines demonstrated that SMARCB1 re-expression significantly reduced MUC16 expression, and that MUC16 knockdown induced apoptosis and reduced cell proliferation. Conclusions: The correlation between serum CA-125 levels and metastatic burden suggests that CA-125 is a clinically relevant biomarker for RMC. These findings support further exploration of CA-125 for disease monitoring and targeted therapeutics in RMC.