Loss-of-function mutations in the Transcription Factor 7 (T cell factor-1) gene in hepatogastrointestinal cancers

Molecular & Cellular Toxicology

Kang Jun Yoon¹  Won Sang Park¹  Jeong Kyu Kim¹  Jung Woo Eun¹  Jang Eun Lee¹  Su Young Kim¹  Sung Hak Lee¹  Suk Woo Nam¹  Jung Young Lee¹  Kwang Hwa Jung¹  Jae Hwi Song¹  Myung Gyu Choi¹  Hyun Jin Bae¹  Sang Woo Kim¹  Ji Heon Noh¹ 

[1] The Catholic University of Korea$$

关键词: Alimentary tract cancers;   

DOI  :  10.1007/s13273-010-0037-y

学科分类：分子生物学，细胞生物学和基因

来源: Korean Society of Toxicogenomics and Toxicoproteomics

【 摘 要 】

Inappropriate activation of the Wnt signaling pathway has been repeatedly implicated in the tumorigenesis of colon, liver, and gastric cancers. There is accumulating evidences that transcriptional factor 7 (TCF7; also called T cell factor 1) might also be one of the tumor suppressor genes in the Wnt pathway. We performed PCR-based sequencing analysis of the TCF7 gene in 234 alimentary tract cancers. The TCF7 mutants detected in this study were functionally analyzed after they were generated by a QuickChange site-directed mutagenesis kit. We detected 7 somatic mutations in the TCF7 gene, including 4 missense, 2 frameshift, and one 28-bp deletion. In a yeast two-hybrid assay, most of the mutants showed varying degrees of decreased binding to an amino-terminal enhancer of split (AES), a truncated form of Groucho-related protein lacking WD40 repeats. To determine whether mutant TCF7 proteins had decreased DNA binding, we performed electrophoretic mobility shift assays, and the 2 frameshift mutants were shown to have no DNA binding activity. Furthermore, luciferase reporter assays revealed that TCF7 mutants in the presence of AES failed in the AES-dependent transcriptional repression of the reporter gene. In addition, human embryonic kidney 293 cells transfected with TCF7 mutants expressed high levels of cyclin D1, up to 6 times more than cells transfected with wild-type TCF7. Therefore, the TCF7 mutations detected in this study seem to be “loss-of-function mutations�? caused by loss of TCF7 repressor activity through decreased binding to Groucho-related protein and/or DNA, thereby contributing to neoplastic transformation by causing accumulation of cylin D1.

【 授权许可】

Unknown