Both MCF-7 and MDA-MB-231 cells, despite being invasive ductal/breast carcinoma cells, represent a conspicuous example as they have phenotypic/genotypic differences: while MCF-7 is hormone-dependent (negative for HER-2 receptor, positive for estrogen and progesterone receptor), MDA-MB-231 is triple negative [28]. This evidence concerns the gene PGR and breast carcinoma.