The expression of PMCA-type calcium pumps also undergoes significant isoform-specific changes during the differentiation of gastric and colon carcinoma cells [219,220,221], PMCA isoenzyme composition of various molecular and histological types of breast carcinoma displays tumor type-specific characteristics [222,223,224,225,226], the PMCA isoenzyme composition of estrogen receptor-positive breast cancer cells is modulated by estradiol [227], and normal breast epithelium also undergoes important changes in terms of PMCA isoenzyme expression during lactation [194,228,229,230,231,232,233]. This evidence concerns the gene ESR1 and breast cancer.