Down-regulation of MutS homolog 3 by hypoxia in human colorectal cancer.

Abstract

Down-regulation of hMSH3 is associated with elevated microsatellite alterations at selected tetranucleotide repeats and low levels of microsatellite instability in colorectal cancer (CRC). However, the mechanism that down-regulates hMSH3 in CRC is not known. In this study, a significant association between over-expression of glucose transporter 1, a marker for hypoxia, and down-regulation of hMSH3 in CRC tissues was observed. Therefore, we examined the effect of hypoxia on the expression of hMSH3 in human cell lines. When cells with wild type p53 (wt-p53) were exposed to hypoxia, rapid down-regulation of both hMSH2 and hMSH3 occurred. In contrast, when null or mutated p53 (null/mut-p53) cells were exposed to hypoxia, only hMSH3 was down-regulated, and at slower rate than wt-p53 cells. Using a reporter assay, we found that disruption of the two putative hypoxia response elements (HREs) located within the promoter region of the hMSH3 abrogated the suppressive effect of hypoxia on reporter activity regardless of p53 status. In an EMSA, two different forms of HIF-1α complexes that specifically bind to these HREs were detected. A larger complex containing HIF-1α predominantly bound to the HREs in hypoxic null/mut-p53 cells whereas a smaller complex predominated in wt-p53 cells. Finally, HIF-1α knockdown by siRNA significantly inhibited down-regulation of hMSH3 by hypoxia in both wt-p53 and mut-p53 cells. Taken together, our results suggest that the binding of HIF-1α complexes to HRE sites is necessary for down-regulation of hMSH3 in both wt-p53 and mut-p53 cells.

• Authors: Jie Li, Junichi Koike, Hiroyuki Kugoh, Michitsune Arita, Takahito Ohhira, Yoshinori Kikuchi, Kimihiko Funahashi, Ken Takamatsu, C Richard Boland, Minoru Koi, Hiromichi Hemmi
• Journal: Biochimica et biophysica acta (Biochim Biophys Acta) Vol. 1823 Issue 4 Pg. 889-99 (Apr 2012) ISSN: 0006-3002 [Print] Netherlands
• PMID: 22343000 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2012 Elsevier B.V. All rights reserved.

Chemical References

• DNA-Binding Proteins
• Glucose Transporter Type 1
• Hypoxia-Inducible Factor 1, alpha Subunit
• MSH3 protein, human
• MutS Homolog 3 Protein
• SLC2A1 protein, human
• Tumor Suppressor Protein p53

Topics

• Base Sequence
• Cell Hypoxia (genetics)
• Cell Line, Tumor
• Colorectal Neoplasms (genetics, pathology)
• DNA-Binding Proteins (genetics, metabolism)
• Down-Regulation (genetics)
• Gene Expression Regulation, Neoplastic
• Genes, Reporter
• Glucose Transporter Type 1 (metabolism)
• Humans
• Hypoxia-Inducible Factor 1, alpha Subunit (metabolism)
• Molecular Sequence Data
• MutS Homolog 3 Protein
• Promoter Regions, Genetic (genetics)
• Protein Binding (genetics)
• Response Elements (genetics)
• Tumor Suppressor Protein p53 (metabolism)