Abstract 318: Identification of FERM domain-containing protein 5 (FRMD5) as a novel target of β-catenin/TCF7L2 complex

Abstract

Abstract Deregulated Wnt signaling is one of the earliest steps in colorectal tumorigenesis. The impairment results most frequently from APC mutations, which leads to the accumulation of β-catenin and subsequent activation of TCF7L2. Although previous studies have identified a number of target genes of the activated β-catenin/TCF7L2 transcriptional complex such as cMYC and CCND1, the comprehensive effect of the activation on tumorigenesis remains to be elucidated. To understand the precise molecular mechanisms underlying colorectal cancer, we searched for novel genes regulated by the complex in colorectal tumors. We performed expression profile analysis of HCT116 and SW480 colon cancer cells treated with β-catenin siRNAs, and combined these data with public microarray data of LS174 cells treated with a dominant-negative form of TCF7L2. As a result, we identified a total of 134 genes that were regulated by both β-catenin and TCF7L2. Subsequent ChIP-sequence with TCF7L2 antibody selected 11 genes from the 134 genes as candidates of direct target genes. In this study, we focused on FERM domain-containing protein 5 (FRMD5) among the 11 candidates. Quantitative PCR confirmed that its expression was reduced by β-catenin siRNA in HCT116 and SW480 cells. ChIP-quantitative PCR analysis with ant-TCF7L2 antibody also corroborated the interaction of TCF7L2 with a region (hg19; chr15:44,449,680-44,450,487) within intron 1 of FRMD5. Reporter assay with plasmids containing this region revealed that the reporter activity was down-regulated by the knockdown of β-catenin. These data suggested that FRMD5 is a direct target of β-catenin/TCF7L2 complex, and that the region is involved in the transcriptional activation through an interaction with the complex. Consistently, its expression was elevated in colorectal tumors compared to normal colonic mucosa in public microarray data. To uncover the role of FRMD5 in colorectal carcinogenesis, we analyzed expression profile of HCT116 cells treated with FRMD5 siRNA, and combined the data with profile with β-catenin siRNA. Gene set analysis with 53 commonly up-regulated and 36 commonly down-regulated genes by both FRMD5 and β-catenin disclosed that the gene sets of DNA replication, cell cycle, and extracellular matrix (ECM) were altered by FRMD5. These data may be useful for the future studies of colorectal carcinogenesis. Citation Format: Yoichi Furukawa, Chi Zhu, Tomoyuki Ohsugi, Yumi Terakado, Rei Noguchi, Tsuneo Ikenoue, Kiyoshi Yamaguchi. Identification of FERM domain-containing protein 5 (FRMD5) as a novel target of β-catenin/TCF7L2 complex [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 318. doi:10.1158/1538-7445.AM2017-318