PTGS2 and breast adenocarcinoma: The model was tested in two different human cell lines: MCF-7, an estrogen responsive cell line derived from metastatic human breast adenocarcinoma, which is known to express PTGS2 (12), and HEK293FT, a highly transfectable clonal isolate derived from human embryonal kidney cells HEK293, which does not constitutively express PTGS2 (13).