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Hypermethylation of calcitonin gene regulatory sequences in human breast cancer as revealed by genomic sequencing
Author(s) -
Hakkarainen Mika,
Wahlfors Jarmo,
Myöhänen Sanna,
Hiltunen Mikko O.,
Eskelinen Matti,
Johansson Risto,
Jänne Juhani
Publication year - 1996
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/(sici)1097-0215(19961220)69:6<471::aid-ijc9>3.0.co;2-1
Subject(s) - dna methylation , methylation , biology , cancer research , epigenetics , cancer , breast cancer , gene , gene expression , genetics
DNA methylation has been studied intensively during the past years in order to elucidate its role in the regulation of gene expression, gene imprinting and cancer progression. Earlier studies have shown that a general genomic under‐methylation is associated with chronic lymphocytic leukemia and metastatic prostate cancer. Site‐specific methylation changes, as revealed by the use of methylation‐sensitive restriction enzymes, have been reported to occur in the promotor region of the calcitonin gene in chronic myeloid leukemia as it progresses from the chronic phase to blast crisis, in non‐Hodgkin's lymphoid neoplasms and in non‐lymphocytic leukemia. We have now explored possible methylation changes associated with benign and malignant breast tumors. Two approaches were employed: (i) chemical determination of general genomic methylation status and (ii) base‐specific analysis of the methylation changes in the promoter of the calcitonin gene with the aid of genomic sequencing. The results did not reveal any changes of total DNA 5‐methylcytosine content in ductal carcinoma of breast in comparison with benign tumors. There was a small, yet significant, increase in 5‐methylcytosine content in lobular carcinoma. Genomic sequencing of the promoter region of the calcitonin gene, however, revealed a striking hypermethylation at or around the transcription start site of the gene in ductal carcinomas. In benign tumors and lobular carcinomas, this region was either entirely unmethylated or only slightly methylated. The latter changes may reflect a regional hypermethylation of the short arm of chromosome II, which harbors, in addition to the calcitonin gene, a number of putative or established tumor‐suppressor genes. Our results demonstrate that genomic sequencing in its present form can be used for a reliable and precise DNA methylation analysis of primary human tumors. © 1996 Wiley‐Liss, Inc.