Abstract 272: Transcriptional regulation of REG4, a novel diagnostic marker of gastrointestinal cancer, by CDX2

Abstract

Regenerating gene family, member 4 (REG4, encodes Reg IV), was originally identified from cDNA library of inflammatory bowel disease tissues, and is specifically expressed in gastrointestinal tract. We have identified REG4 as an overexpressed gene in gastric cancer from SAGE analysis in gastric cancer tissues and noticed as a novel serum marker of cancer. The expression of Reg IV is associated with intestinal mucin differentiation, and RegIV is expressed in CDX2-positive cells. CDX2, the intestine-specific caudal-related homeobox transcription factor, plays a key role in intestinal development and differentiation. In the present study, we investigated whether CDX2 induce RegIV expression. Western blot analysis indicated that forced expression of CDX2 in HT29 colon cancer cell line induced Reg IV expression. In silico analysis of 2-kilobase upstream region of REG4 revealed at least four putative CDX2 consensus sequences. To assess the role of these putative CDX2 consensus sequences in regulating REG4 transcription, we performed luciferase assay into HSC39 gastric cancer cell line, in which CDX2 is highly expressed. Reporter gene constructs containing 2-kilobase of 5’-flanking region from the REG4 gene showed strong reporter activity. Significant change of reporter activity was not observed between 2.0 and 0.65-kilobase upstream region of REG4 constructs, apart from that significant lower expression level at 0.1-kilobase. These results suggest that expression of REG4 is regulated by CDX2, and upstream region of REG4 has enhancer sequences at proximal region at 0.1-kilobase upstream region. Based on the analysis of single mutation in the putative CDX2 consensus sequences in the 5’-flanking region of the REG4 gene, two putative CDX2 consensus sequences were found to activate REG4 expressions. Therefore, RegIV may be a key factor mediating CDX2 function in intestinal determination. To identify the CDX2-binding site in detail, ChIP assay and mutagenesis with multiple mutations in the putative CDX2 consensus sequences must be carried out. 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 272. doi:10.1158/1538-7445.AM2011-272