Inhibition of human ovarian cancer cell proliferation in vitro by neuroendocrine hormones.

Direct inhibitory effects of neuroendocrine hormones on human ovarian cancer cell proliferation in vitro were examined. Except for melatonin, all neuroendocrine hormones used in this study inhibited proliferation of KF cells derived from human serous cystadenocarcinoma of the ovary in a dose-dependent manner. The degree of inhibition of prostaglandin D2 was most marked being comparable to that of 5-fluorouracil and followed by beta-endorphin, alpha-endorphin, and Met-enkephalin. More than 200 microM melatonin stimulated the cell proliferation. The inhibitory effects by endorphins were partially reversible by 20 microM naloxone. From analyses of uptakes of radiolabeled precursors by the KF cell, endorphins were considered to inhibit protein and RNA syntheses but not DNA synthesis. These results suggest that neuroendocrine hormones may play an important role in regulation of tumor growth.