In order to evaluate whether the vitamin D treatment correlates with the Cdx2 status and presence/absence of ER, we selected 6 representative ER(–) breast cancer cell lines characterized by different polymorphisms: AA (SK-BR3 and MDA-MB-468), AG (MDA-MB-231 and SUM159PT), GG (BT20 and HCC1954) and two ER(+) breast cancer cell lines with AG status of Cdx2 (MCF7 and T47-D). Here, ESR1 is linked to breast cancer.