For that, we selected three BC cell lines representative of the main BC subtypes: (i) MCF7 (ER+, PR+, HER-2–), corresponding to the most common BC type—Luminal A; (ii) SKBR3 (ER–, PR–, HER-2+), representing the HER-2 subtype; and (iii) MDA-MB-231, a triple-negative cell line (ER–, PR–, HER-2–), equivalent to TNBC [52,53]. This evidence concerns the gene PGR and breast cancer.