Keith Wilson
Faculty Member
Last active: 12/19/2020

Distinct methylation patterns of two APC gene promoters in normal and cancerous gastric epithelia.

Tsuchiya T, Tamura G, Sato K, Endoh Y, Sakata K, Jin Z, Motoyama T, Usuba O, Kimura W, Nishizuka S, Wilson KT, James SP, Yin J, Fleisher AS, Zou T, Silverberg SG, Kong D, Meltzer SJ
Oncogene. 2000 19 (32): 3642-6

PMID: 10951570 · DOI:10.1038/sj.onc.1203704

The adenomatous polyposis coli (APC) tumor suppressor gene is mutationally inactivated in both familial and sporadic forms of colorectal cancers. In addition, hypermethylation of CpG islands in the upstream portion of APC, a potential alternative mechanism of tumor suppressor gene inactivation, has been described in colorectal cancer. Because a subset of both gastric and colorectal cancers display the CpG island methylator phenotype, we hypothesized that epigenetic inactivation of APC was likely to occur in at least some gastric cancers. APC exhibits two forms of transcripts from exons 1A and 1B in the stomach. Therefore, we investigated CpG island methylation in the sequences upstream of exons 1A and 1B, i.e., promoters 1A and 1B, respectively. We evaluated DNAs from 10 gastric cancer cell lines, 40 primary gastric cancers, and 40 matching non-cancerous gastric mucosae. Methylated alleles of promoter 1A were present in 10 (100%) of 10 gastric cancer cell lines, 33 (82.5%) of 40 primary gastric cancers, and 39 (97.5%) of 40 noncancerous gastric mucosae. In contrast, promoter 1B was unmethylated in all of these same samples. APC transcripts from exon 1A were not expressed in nine of the 10 methylated gastric cancer cell lines, whereas APC transcripts were expressed from exon 1B. Thus, expression from a given promoter correlated well with its methylation status. We conclude that in contrast to the colon, methylation of promoter 1A is a normal event in the stomach; moreover, promoter 1B is protected from methylation in the stomach and thus probably does not participate in this form of epigenetic APC inactivation.

MeSH Terms (15)

Adolescent Base Sequence DNA, Neoplasm DNA Methylation Female Gastric Mucosa Gene Expression Genes, APC Humans Molecular Sequence Data Promoter Regions, Genetic RNA, Messenger RNA, Neoplasm Stomach Neoplasms Tumor Cells, Cultured

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