GPR68 and invasive ductal breast carcinoma: Upon validation of this data with qPCR, the triple-negative adenocarcinoma MDA-MB-231 showed the highest expression of GPR68 at the mRNA level, followed by the luminal A MCF-7 cell line, followed by Her2+ SkBr3 and lastly the triple-negative invasive ductal carcinoma BT-549 (Figure 6B).