Abstract 2091: DNA methylation enhances apoptosis resistance of renal cancer cells

Epigenetic modifications are important not only for carcinogenesis but also for metastasis of clear cell renal cell carcinoma (ccRCC). We previously reported that inflammation-related signaling is constitutively activated in advanced ccRCC through the formation of super enhancer. In addition to histone modification, methylation of the primary structure of DNA is implicated in the progression of ccRCC. Recent studies revealed that DNA hypermethylation was frequently observed in ccRCC and correlated with poor prognosis. However, unlike in other cancers, methylated genes responsible for cancer progression is still unclear in ccRCC. In this study, we tried to identify a target(s) for DNA methyltransferases (DNMTs) in ccRCC cells based on the genome-wide analysis. Its function for the regulation of cellular survival was examined. Our preclinical model of ccRCC using the serial orthotopic inoculation model exhibited the up-regulation of DNMT3B in advanced ccRCC. Pre-treatment of advanced ccRCC with 5-aza-dC attenuated a formation of a primary tumor through the induction apoptosis. DNA methylated sites were analyzed using methylation array in reference to RNA-sequencing data. As a result, ubiquinol cytochrome c reductase hinge protein (UQCRH), one of the components of mitochondrial complex III, was extracted as a methylation target in advanced ccRCC. Immunohistochemical analysis revealed that the expression of UQCRH in human ccRCC tissue was lower than normal adjacent tissue. Silencing of UQCRH attenuated the cytochrome c release in response to apoptotic stimuli and resulted in enhancement of primary tumor formation in vivo. Our results imply that DNA methylation induces the decreased expression of potential tumor suppressor gene UQCRH, which is essential for the completion of apoptotic process of ccRCC cells. These findings may contribute to the understanding of molecular mechanisms involved in the drug resistance of ccRCC cells and provide an important insight for the improvement of the efficacy of existing medicines. Citation Format: Kosuke Miyakuni, Jun Nishida, Shogo Ehata, Kohei Miyazono. DNA methylation enhances apoptosis resistance of renal cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2091.