PTGS2 and breast carcinoma: Researchers also found high expression of COX-2 in highly invasive estrogen independent breast cancer cell lines, (MDA-MB-231 (MDA-231) and Hs578T) as well as 12, 0-tetradecanoylphorbol-13-acetate (TPA)-induced COX-2 expression, while a poorly invasive and estrogen dependent cell line (MCF-7) did not express COX-2 [2,2,3].