Aberrant promoter methylation may be responsible for the control of CD146 (MCAM) gene expression during breast cancer progression

The CD146 (also known as MCAM, MUC-18, Mel-CAM) was initially reported on in 1987, as a protein crucial for melanoma invasion. Recently, it has been confirmed that CD146 is involved in progression and poor overall survival of many other cancers, including breast cancer. Importantly, in independent studies, CD146 was reported to be a trigger of epithelial to mesenchymal transition in breast cancer cells. The goal of our current study was to verify possible involvement of an epigenetic mechanism behind regulation of the CD146 expression in breast cancer cells, as it has been previously reported for prostate cancer. First, we analysed the response of breast cancer cells, varying in the initial CD146 mRNA and protein content, to an epigenetic modifier, 5-aza-2-deoxycytidine, and subsequently the methylation status of CD146 gene promoter was investigated, using direct bisulfite sequencing. We observed that treatment with a demethylating agent led to induction of CD146 expression in all analysed breast cancer cell lines, both at the mRNA and protein levels, which was accompanied by an elevated expression of selected mesenchymal markers. Importantly, CD146 gene promoter analysis showed aberrant CpG island methylation in 2 out of 3 studied breast cancer cells lines, indicating epigenetic regulation of the CD146 gene expression. In conclusion, our study revealed for the first time that aberrant methylation may be involved in expression control of CD146, a very potent EMT inducer in breast cancer cells. Altogether, the data obtained may provide basis for novel therapies, as well as diagnostic approaches enabling sensitive and very accurate detection of breast cancer cells. v