Next, the relative HIF-1α expression levels were determined by western blotting in five human breast cancer cell lines including MCF-7, T47D, SKBR3, MDA-MB-231 (two strains stored in different laboratories) and BT549, of which MCF-7 and T47D are characterized as ER-positive/PgR-positive luminal mammary carcinoma, MDA-MB-231 and BT-549 are characterized as triple-negative/basal-B mammary carcinoma (TNBC), and SKBR3 is a cell line that overexpresses the Her2 (Neu/ErbB-2) gene product. Here, PGR is linked to breast cancer.