Abstract 4702: DNA methylation enhances apoptosis resistance of renal cancer cells through the control of mitochondria related gene expression

Many gene alterations have been identified in the onset of renal carcinogenesis. However, molecular alterations might be added to renal cancer cells during the progression. In order to uncover additional molecular alterations, we established highly malignant cancer cells which possess identical background to original cancer cells, and analyzed them in the present study. Since our previous works demonstrated that interaction with cancer microenvironment aids cancer cells with malignant trait through “education” and “selection”, serial orthotopic transplantation was utilized. First, parental human clear cell renal cell carcinoma cells, OS-RC-2, were subjected to serial orthotopic transplantation. Then, novel derivatives were obtained from resulting primary renal tumors. These derivatives formed primary renal tumor faster than parental cells and exhibited increased lung metastasis, suggesting that these derivatives were defined as “highly malignant cancer cells”. Next, we tried to identify the underlying molecular mechanism(s) for renal cancer progression through the characterization of highly malignant cancer cells. Gene expressions in each cell were profiled using RNA-sequencing, and these analyses revealed that expression of several genes associated with mitochondrial functions were dramatically down-regulated in highly malignant cancer cells. Since mitochondrial electron transport chain triggers apoptotic cell death, decrease of these genes may contribute to suppression of apoptosis of highly malignant cancer cells. Cell culture and in vivo experiments demonstrated that mitochondrial dysfunction is responsible for increased survival of renal cancer cells and cancer metastasis. Finally, regulatory mechanism of downregulation of these mitochondria-related genes was analyzed. Bisulfite sequencing analysis revealed that the downregulation may occur by DNA hypermethylation of CpG islands in the promoter regions in renal cancer cells.Taken together, these findings suggested that renal cancer cells acquire additional anti-apoptotic ability through the DNA methylation during the interactions with renal microenvironment, which may in turn lead to the cancer progression and metastasis. We are currently investigating whether the effect of anti-cancer reagent is enhanced in the presence of DNA methylation inhibitors. Citation Format: Kosuke Miyakuni, Jun Nishida, Shogo Ehata, Kohei Miyazono. DNA methylation enhances apoptosis resistance of renal cancer cells through