Abstract 102: Hypermethylation ofKeap1promoter and expression of the downstream genes in human colorectal cancer cell lines

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Nrf2-Keap1 system is a master regulator of phase 2 detoxifying and antioxidant genes including NAD(P)H-quinon oxidoreductase 1[NQO-1] and aldo-keto reductase C1 (AKRC1). Somatic mutation of Keap1 gene and aberrant hypermethylation of Keap1 gene promoter region was found in human lung cancer. Loss of keap1 function activates Nrf2 activity and enhanced the lung cancer cell growth in vitro and in vivo. However, there has not been studied Keap1 gene status in colorectal cancer. In this study, we investigated status of keap1 gene in 10 human colorectal cancer cell lines. No somatic mutation of keap1 gene was found in all 10 cell lines. Hypermethylation of Keap1 promoter region was found in 8 cell lines. Keap1 mRNA and protein expression tended to be lower in these hypermethylated cell lines. The keap1 mRNA in a methylated cell line (HT29) was re-expressed by treatment with the DNA methylation inhibitor 5-aza-2’-deoxycytidine (5-azadC) and Trichostatin A (TSA). mRNA of the downstream genes, such as NQO-1 and AKRC1, were over expressed in the methylated cell line (HT29) compared to a nonmethylated cell line (Colo320DM) in Real time PCR analysis. In addition, we examined the methylation status of keap1 promoter region in primary tumors of 30 patients with colorectal cancer using methylation-specific PCR. An aberrant methylation in keap1 promoter was detected in 16 of 30 (53%). These findings suggest that hypermethylation of Keap1 promoter region in human colorectal cancer upregulates the expression of the downstream genes of keap1/nrf2 system which can be associated with the advantage for cancer progression and resistance to the anticancer agents. 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 102. doi:10.1158/1538-7445.AM2011-102