Since our set of breast tissue samples contained only one tumor of a triple negative subtype, we determined the methylation status of CDKN2A exon 2 in MDA-MB-231, a triple negative breast cancer cell line and compared it with the methylation status of the ER positive cell lines MCF-7 (luminal A) and ZR-75-1 (luminal B). Here, ESR1 is linked to breast carcinoma.