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Methylation of CpG loci in 5′‐flanking region alters steady‐state expression of adenomatous polyposis coli gene in colon cancer cell lines
Author(s) -
Sakamoto Yoshio,
Kitazawa Riko,
Maeda Sakan,
Kitazawa Sohei
Publication year - 2000
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/1097-4644(20010301)80:3<415::aid-jcb150>3.0.co;2-5
Subject(s) - biology , adenomatous polyposis coli , epigenetics , microbiology and biotechnology , cpg site , methylation , carcinogenesis , dna methylation , northern blot , gene expression , gene , cancer research , cancer , genetics , colorectal cancer
The APC genetic locus has been linked to the tumorigenesis and progression of colorectal cancer, although the precise mechanism of its involvement in this disease remains unknown. We used high sensitivity mapping of the methylated cytosine, Northern blot analysis and immunocytochemical staining in six colorectal cancer cell lines (DLD‐1, SW480, Colo320, HT29, WiDr, and Colo201) to examine the relationship between the methylation status of the CpG loci in the 5′‐flanking region of the APC gene and its expression. APC mRNA expression levels determined by Northern blot analysis correlated well with APC protein levels visualized by immunocytochemistry. In these colorectal cancer cell lines, no major genetic alterations of the APC gene, such as amplification or deletion, were detected. Analysis of the epigenetic control of APC gene expression in these lines revealed that methylation of the CpG loci in the 5′‐untranslated region of APC mRNA repressed steady‐state expression of the gene. Furthermore, epigenetic alteration of the APC gene was independent of the APC protein truncation and CpG methylation of the hMLH1 promoter. Although less eminent than protein truncation by point mutation within the coding region of the APC gene, epigenetic alteration suppressing APC gene expression may significantly contribute to oncogenesis and the progression of colorectal cancer. J. Cell. Biochem. 80:415–423, 2001. © 2001 Wiley‐Liss, Inc.