Progestin-induced apoptosis in the Macaque ovarian epithelium: differential regulation of transforming growth factor-beta
BACKGROUND: Oral contraceptive (OC) use is associated with a reduced risk of ovarian cancer. An OC component, progestin, induces apoptosis in the primate ovarian epithelium. One regulator of apoptosis is transforming growth factor-beta (TGF-beta). We determined the effect of progestin on TGF-beta expression in the primate ovarian epithelium and examined the relationship between TGF-beta expression and apoptosis. METHODS: Female cynomolgus macaques were randomly assigned to receive a diet for 35 months containing no hormones (n = 20); the OC Triphasil (n = 17); or each of its constituents, ethinyl estradiol (estrogen, n = 20) or levonorgestrel (progestin, n = 18 ), alone. Ovarian sections were immunostained with monoclonal antibodies against TGF-beta1 or TGF-beta2 plus TGF-beta3 (TGF-beta2/3) isoforms. The expression of TGF-beta isoforms in four ovarian compartments (epithelium, oocytes, granulosa cells, and hilar vascular endothelium) was compared among treatment groups. The association between TGF-beta expression and apoptosis, as determined by morphology and histochemistry, was examined in ovarian epithelium. All statistical tests were two-sided. RESULTS: Compared with ovaries from the control and estrogen-only-treated monkeys, the ovaries of progestin-treated monkeys showed 1) a marked decrease in the expression of TGF-beta1 and a concomitant increase in the expression of the TGF-beta2/3 isoforms in the ovarian epithelium (P<.001), 2) an increase in the expression of TGF-beta2/3 in the hilar vascular endothelium (P<.001), and 3) a marked decrease in TGF-beta2/3 expression in granulosa cells (P<.001). The apoptotic index of the ovarian epithelium was highly associated with the change in expression from TGF-beta1 (P<.001) to TGF-beta2/3 (P</=.002) induced by progestin treatment. CONCLUSIONS: Progestin induces differential regulation in the ovarian epithelium of TGF-beta, a change in the expression of which is highly associated with apoptosis. These data suggest a possible biologic mechanism for the protective association between OC use and reduced ovarian cancer risk
Rodriguez, GC., Nagarsheth, NP., Lee, KL., Bentley, RC., Walmer, DK., Cline, M., ... Hughes, C. (2002). Progestin-induced apoptosis in the Macaque ovarian epithelium: differential regulation of transforming growth factor-beta. Journal of the National Cancer Institute, 94(1), 50-60.