ESR1 and breast cancer: Subsequently, we measured both mRNA and protein levels of PRSS23 in 8 different human cell lines: 3 ERα-positive breast cancer cell lines (MCF-7, BT-474, T-47D), 2 ERα-negative breast cancer lines (Hs.578t, MDA-MB-231), 1 mammary epithelial cell line (MCF-10A), 1 endometrial cell line (RL95-2), and 1 cervical cancer line (Ca-SKi).