Abstract 1343: Protective effect of catechol-O-methyltransferase in human renal cell carcinogenesis

Abstract

Abstract Exposure to carcinogenic catechol estrogens plays a role in the development of kidney cancer. Catechol-O-methyltransferase (COMT) neutralizes the genotoxic effects of these compounds by methoxylation. Although reduced activity of COMT has been suggested as a risk factor for estrogen-associated cancers, its critical role in kidney cancer and underlying mechanisms of renal cell carcinogenesis are largely unknown. To address the role and function of COMT in renal cell carcinomas (RCC), we initially determined levels of COMT in normal kidney and clear cell RCC. The expression of COMT mRNA was down-regulated in clear cell RCC tissues as determined by quantitative PCR. Low expression of COMT protein in clear cell RCC tissues was also confirmed by immunohistochemical counting of staining score (2.5 vs. 0.5 in normal kidney and clear cell RCC, respectively, p<0.001). Since COMT expression is reduced in clear cell RCC compared to normal cells, we explored the function of COMT by transiently over-expressing it in the Caki-1 clear cell RCC cell line with low levels of COMT compared to HK-2 normal renal cells. A significant increase of COMT expression in Caki-1 cells (Caki-1/COMT) compared to parent cells transfected with vector control (Caki-1/pCMV6) was confirmed by both quantitative PCR and Western blot. We investigated the role of COMT on cell proliferation and found that proliferation of Caki-1/COMT cells was decreased by 8 to 15 % in a time dependent manner (from 24 hours to 72 hours, p<0.05). We also assessed the effect of COMT on cell cycle progression by flow cytometry. Over-expression of COMT led to an increase (8 ± 1.6%) in the G0/G1 phase population, whereas the number of cells in S-phase decreased from 5.5 % to 2.6 % (p<0.05). These data indicate that COMT over-expression ameliorate the proliferation of Caki-1 renal cancer cell line by G0/G1 phase arrest. In addition, we analyzed whether COMT expression affects apoptosis of Caki-1 cells by flow cytometry using annexin V-FITC/7-AAD (7-amino actinomycin D) dye. COMT expression resulted in a higher percentage of cells undergoing both early and late apoptosis compared to vector controls (2.3% vs. 0.4 %, respectively for early apoptosis, and 5.5 % vs. 0.8 %, respectively for late apoptosis, p<0.05). Our study indicates that COMT plays a protective role in renal cell carcinogenesis by preventing cellular proliferation and enhancing apoptosis of RCC cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1343. doi:10.1158/1538-7445.AM2011-1343