Paper Title
In-Vitro Determination of the Biological Basis of Protection by Progesterone in Melanoma based on Mouse and Human Melanoma Cell Models

Abstract
Melanoma is a fatal form of skin cancer. Epidemiological SEER data showed a higher mortality rate in males than in females. Clinical studies showed that menstruating females were better protected in melanoma than post-menopausal women and men of any age, suggesting the involvement of sex steroid hormones in the protection. But clinical studies did not show any direct effect of sex steroids on melanoma. Our previous studies with mouse and human melanoma cell lines showed a direct effect of progesterone in inhibiting the cell growth in-vitro significantly. This observation raised the question, whether androgens were responsible for increased male mortality in melanoma? But, dose curve studies of androgens (androstenedione and testosterone) showed a dose-dependent inhibition of mouse melanoma cells, suggesting androgens also inhibited melanoma cell growth. As inhibition of melanoma cell growth by progesterone was already known, co-incubation of progesterone (10 M) with androgens was carried out. It showed an additive effect on mouse melanoma cell growth inhibition. This result suggested that lack or deficiency of progesterone in males could be responsible for increased male mortality. Literature survey showed that progesterone level was very low (27-90 ng/dl) in males, the group which lacked protection in melanoma according to the clinical studies. In-vitro experiments along with literature survey and clinical studies prompted us to postulate that progesterone could be involved in the protection in melanoma. So the study was extended to human melanoma (BLM) cells. Androgens showed inhibition of human melanoma cell growth, though at higher concentrations (100 and 200 M). Addition of 10 M of progesterone to androgens showed an additive effect on human melanoma cell growth inhibition, indicating a protective function of progesterone. In order to further investigate the protective functions of progesterone, in-vitro adhesion and migration assays were carried after co-incubation of melanoma cells with androgens and progesterone. Protective effects were shown by the significant decrease in adhesion (61%) and migration (7%) functions of co-incubated cells compared to respective control cells (100%). Biochemical basis of this protective functions of progesterone was checked by carrying out an Elisarray, which showed a specific suppression of IL-8 cytokine secretion. Conclusion: Progesterone by suppressing IL-8 cytokine secretion, could be protecting menstruating females in melanoma by decreasing melanoma cell growth, adhesion and migration (essential for metastasis) functions.