Abstract
Hypomethylation of the global genome, considered to be composed mainly of repetitive sequences, is consistently observed in cancers, and aberrant hypo‐ and hypermethylation of CpG islands (CGIs) in promoter regions are also observed. Since methylation alterations in unique promoter sequences and in other genomic regions have distinct consequences, we analyzed the relationship between the global hypomethylation and the hypomethylation of unique promoter CGIs using human gastric cancers. Seven of ten gastric cancer cell lines showed marked decreases in 5‐methylcytosine content, which correlated with hypomethylation of the LINE1 repetitive sequence. Six of the seven cell lines showed hypomethylation in five or all of the six normally methylated CGIs in promoter regions of six genes, and this was associated with induction of aberrant expression. The remaining three cell lines without global hypomethylation showed promoter hypomethylation in one or none of the six CGIs. Frequent promoter hypomethylation, however, did not correlate with frequent promoter hypermethylation. In primary gastric cancers too, global hypomethylation was associated with hypomethylation of LINE1 repetitive sequence and promoter hypomethylation. Of 93 gastric cancers, 33 cancers with frequent promoter hypomethylation and 27 cancers with frequent promoter hypermethylation constituted different groups. These findings represent experimental evidence that frequent hypomethylation of normally methylated promoter CGIs is associated with global hypomethylation, and that these hypomethylations occur independently of frequent promoter CGI hypermethylation. (Cancer Sci 2004; 95: 58–64)
References
- 1. Gama‐Sosa MA, Slagel VA, Trewyn RW, Oxenhandler R, Kuo KC, Gehrke CW, Ehrlich M. The 5‐methylcytosine content of DNA from human tumors. Nucl Acids Res 1983; 11: 6883–94. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2. Feinberg AP, Vogelstein B. Hypomethylation distinguishes genes of some human cancers from their normal counterparts. Nature 1983; 301: 89–92. [DOI] [PubMed] [Google Scholar]
- 3. Jurgens B, Schmitz‐Drager BJ, Schulz WA. Hypomethylation of L1 LINE sequences prevailing in human urothelial carcinoma. Cancer Res 1996; 56: 5698–703. [PubMed] [Google Scholar]
- 4. Takai D, Yagi Y, Habib N, Sugimura T, Ushijima T. Hypomethylation of LINE1 retrotransposon in human hepatocellular carcinomas, but not in surrounding liver cirrhosis. Jpn J Clin Oncol 2000; 30: 306–9. [DOI] [PubMed] [Google Scholar]
- 5. Dunn BK. Hypomethylation: one side of a larger picture. Ann N Y Acad Sci 2003; 983: 28–42. [DOI] [PubMed] [Google Scholar]
- 6. Lander ES, Linton LM, Birren B, Nusbaum C, Zody MC, Baldwin J, Devon K, Dewar K, Doyle M, FitzHugh W, Funke R, Gage D, Harris K, Heaford A, Howland J, Kann L, Lehoczky J, LeVine R, McEwan P, McKernan K, Meldrim J, Mesirov JP, Miranda C, Morris W, Naylor J, Raymond C, Rosetti M, Santos R, Sheridan A, Sougnez C et al. Initial sequencing and analysis of the human genome. Nature 2001; 409: 860–921. [DOI] [PubMed] [Google Scholar]
- 7. de Smet C, Lurquin C, Lethe B, Martelange V, Boon T. DNA methylation is the primary silencing mechanism for a set of germ line‐ and tumor‐specific genes with a CpG‐rich promoter. Mol Cell Biol 1999; 19: 7327–35. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8. van der Bruggen P, Traversari C, Chomez P, Lurquin C, De Plaen E, Van den Eynde B, Knuth A, Boon T. A gene encoding an antigen recognized by cy‐tolytic T lymphocytes on a human melanoma. Science 1991; 254: 1643–7. [DOI] [PubMed] [Google Scholar]
- 9. Takahashi K, Shichijo S, Noguchi M, Hirohata M, Itoh K. Identification of MAGE‐1 and MAGE‐4 proteins in spermatogonia and primary spermatocytes of testis. Cancer Res 1995; 55: 3478–82. [PubMed] [Google Scholar]
- 10. Feinberg AP, Gehrke CW, Kuo KC, Ehrlich M. Reduced genomic 5‐methylcytosine content in human colonic neoplasia. Cancer Res 1988; 48: 1159–61. [PubMed] [Google Scholar]
- 11. Gillespie AM, Coleman RE. The potential of melanoma antigen expression in cancer therapy. Cancer Treat Rev 1999; 25: 219–27. [DOI] [PubMed] [Google Scholar]
- 12. Jones PA, Baylin SB. The fundamental role of epigenetic events in cancer. Nat Rev Genet 2002; 3: 415–28. [DOI] [PubMed] [Google Scholar]
- 13. Shim YH, Kang GH, Ro JY. Correlation of p16 hypermethylation with p16 protein loss in sporadic gastric carcinomas. Lab Invest 2000; 80: 689–95. [DOI] [PubMed] [Google Scholar]
- 14. Fleisher AS, Esteller M, Wang S, Tamura G, Suzuki H, Yin J, Zou TT, Abraham JM, Kong D, Smolinski KN, Shi YQ, Rhyu MG, Powell SM, James SP, Wilson KT, Herman JG, Meltzer SJ. Hypermethylation of the hMLH1 gene promoter in human gastric cancers with microsatellite instability. Cancer Res 1999; 59: 1090–5. [PubMed] [Google Scholar]
- 15. Baylin SB, Herman JG, Graff JR, Vertino PM, Issa JP. Alterations in DNA methylation: a fundamental aspect of neoplasia. Adv Cancer Res 1998; 72: 141–96. [PubMed] [Google Scholar]
- 16. Narayan A, Ji W, Zhang XY, Marrogi A, Graff JR, Baylin SB, Ehrlich M. Hypomethylation of pericentromeric DNA in breast adenocarcinomas. Int J Cancer 1998; 77: 833–8. [DOI] [PubMed] [Google Scholar]
- 17. Kaneda A, Kaminishi M, Yanagihara K, Sugimura T, Ushijima T. Identification of silencing of nine genes in human gastric cancers. Cancer Res 2002; 62: 6645–50. [PubMed] [Google Scholar]
- 18. Ochiai A, Yasui W, Tahara E. Growth‐promoting effect of gastrin on human gastric carcinoma cell line TMK‐1. Jpn J Cancer Res 1985; 76: 1064–71. [PubMed] [Google Scholar]
- 19. Kuo KC, McCune RA, Gehrke CW, Midgett R, Ehrlich M. Quantitative reversed‐phase high performance liquid chromatographic determination of major and modified deoxyribonucleosides in DNA. Nucleic Acids Res 1980; 8: 4763–76. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 20. Gehrke CW, McCune RA, Gama‐Sosa MA, Ehrlich M, Kuo KC. Quantitative reversed‐phase high‐performance liquid chromatography of major and modified nucleosides in DNA. J Chromatogr 1984; 301: 199–219. [DOI] [PubMed] [Google Scholar]
- 21. Ramsahoye BH. Measurement of genome‐wide DNA cytosine‐5 methylation by reversed‐phase high‐pressure liquid chromatography. Methods Mol Biol 2002; 200: 17–27. [DOI] [PubMed] [Google Scholar]
- 22. Herman JG, Graff JR, Myohanen S, Nelkin BD, Baylin SB. Methylation‐specific PCR: a novel PCR assay for methylation status of CpG islands. Proc Natl Acad Sci USA 1996; 93: 9821–6. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 23. Diala ES, Cheah MS, Rowitch D, Hoffman RM. Extent of DNA methylation in human tumor cells. J Natl Cancer Inst 1983; 71: 755–64. [PubMed] [Google Scholar]
- 24. de Smet C, de Backer O, Faraoni I, Lurquin C, Brasseur F, Boon T. The activation of human gene MAGE‐1 in tumor cells is correlated with genome‐wide demethylation. Proc Natl Acad Sci USA 1996; 93: 7149–53. [DOI] [PMC free article] [PubMed] [Google Scholar]