We conclude that progesterone acts via progesterone receptor to regulate ADAMTS 1 production and secretion by differentiated ovarian cancer cells (NIH-OVCAR-3) and in less differentiated cancer cells (ES-2), progesterone receptor inhibitor is able to decrease ADAMTS 1 and 4 in the cell lysate but not in the conditioned medium of ES-2 cells. The gene discussed is PGR; the disease is ovarian carcinoma.