Methylation of the <it>BIN1 </it>gene promoter CpG island associated with breast and prostate cancer

• Main Authors: Kuznetsova Ekaterina B, Kekeeva Tatiana V, Larin Sergei S, Zemlyakova Valeria V, Khomyakova Anastasiya V, Babenko Olga V, Nemtsova Marina V, Zaletayev Dmitry V, Strelnikov Vladimir V
• Format: Article
• Language: English
• Published: Wolters Kluwer Medknow Publications 2007-05-01
• Series: Journal of Carcinogenesis
• Online Access: http://www.carcinogenesis.com/content/6/1/9

<p>Abstract</p> <p>Background</p> <p>Loss of BIN1 tumor suppressor expression is abundant in human cancer and its frequency exceeds that of genetic alterations, suggesting the role of epigenetic regulators (DNA methylation). <it>BIN1 </it>re-expression in the DU145 prostate cancer cell line after 5-aza-2'-deoxycytidine treatment was recently reported but no methylation of the <it>BIN1 </it>promoter CpG island was found in DU145.</p> <p>Methods</p> <p>Methylation-sensitive arbitrarily-primed PCR was used to detect genomic loci abnormally methylated in breast cancer. <it>BIN1 </it>CpG island fragment was identified among the differentially methylated loci as a result of direct sequencing of the methylation-sensitive arbitrarily-primed PCR product and subsequent BLAST alliance. <it>BIN1 </it>CpG island cancer related methylation in breast and prostate cancers was confirmed by bisulphite sequencing and its methylation frequency was evaluated by methylation sensitive PCR. Loss of heterozygosity analysis of the BIN1 region was performed with two introgenic and one closely adjacent extragenic microsatellite markers.<it>BIN1 </it>expression was evaluated by real-time RT-PCR.</p> <p>Results</p> <p>We have identified a 3'-part of <it>BIN1 </it>promoter CpG island among the genomic loci abnormally methylated in breast cancer. The fragment proved to be methylated in 18/99 (18%) and 4/46 (9%) breast and prostate tumors, correspondingly, as well as in MCF7 and T47D breast cancer cell lines, but was never methylated in normal tissues and lymphocytes as well as in DU145 and LNCaP prostate cancer cell lines. The 5'-part of the CpG island revealed no methylation in all samples tested. <it>BIN1 </it>expression losses were detected in MCF7 and T47D cells and were characteristic of primary breast tumors (10/13; 77%), while loss of heterozygosity was a rare event in tissue samples (2/22 informative cases; 9%) and was ruled out for MCF7.</p> <p>Conclusion</p> <p><it>BIN1 </it>promoter CpG island is composed of two parts differing drastically in the methylation patterns in cancer. This appears to be a common feature of cancer related genes and demands further functional significance exploration. Although we have found no evidence of the functional role of such a non-core methylation in <it>BIN1 </it>expression regulation, our data do not altogether rule this possibility out.</p>