Effect of progestins on immunity: medroxyprogesterone but not norethisterone or levonorgestrel suppresses the function of T cells and pDCs.

OBJECTIVES: The potential effect of hormonal contraception on HIV-1 acquisition and transmission represents an important public health issue. Several observational studies have suggested an association between the use of hormonal contraception, in particular injectable depot medroxyprogesterone acetate (DMPA), and an increased risk of HIV-1 acquisition and transmission. We and others have previously demonstrated that DMPA acts as a potent inhibitor of innate and adaptive immune mechanisms. The study presented here addresses the immunomodulatory properties of several common progestins with a potential to replace DMPA. STUDY DESIGN: To identify safe alternatives to DMPA, we tested the effect of commonly used progestins on the function of human primary T cells and plasmacytoid dendritic cells (pDCs) obtained from the blood of healthy premenopausal women. RESULTS: Medroxyprogesterone acetate (MPA) inhibited the activation of T cells and pDCs in response to T cell receptor- and Toll-like receptor-mediated activation at physiological concentrations. Etonogestrel exerted a partial suppressive activity at high concentrations. In sharp contrast, norethisterone (NET) and levonorgestrel (LNG) did not exhibit detectable immunosuppressive activity. CONCLUSION: Evidence indicating the immunosuppressive properties of DMPA strongly suggests that DMPA should be discontinued and replaced with other forms of long-term contraception. Since NET and LNG do not exert immunosuppressive properties at physiological concentrations, these progestins should be considered as alternative contraceptives for women at high risk for HIV-1 infection. IMPLICATIONS: The presented data suggest that, at physiological levels, the progestins NET and LNG do not suppress cytokine production by immune cells and should be considered as alternatives to DMPA; however, more in vivo testing is needed to confirm this data.

Apigenin induces apoptosis and blocks growth of medroxyprogesterone acetate-dependent BT-474 xenograft tumors.

Recent clinical and epidemiological evidence shows that hormone replacement therapy (HRT) containing both estrogen and progestin increases the risk of primary and metastatic breast cancer in post-menopausal women while HRT containing only estrogen does not. We and others previously showed that progestins promote the growth of human breast cancer cells in vitro and in vivo. In this study, we sought to determine whether apigenin, a low molecular weight anti-carcinogenic flavonoid, inhibits the growth of aggressive Her2/neu-positive BT-474 xenograft tumors in nude mice exposed to medroxyprogesterone acetate (MPA), the most commonly used progestin in the USA. Our data clearly show that apigenin (50 mg/kg) inhibits progression and development of these xenograft tumors by inducing apoptosis, inhibiting cell proliferation, and reducing expression of Her2/neu. Moreover, apigenin reduced levels of vascular endothelial growth factor (VEGF) without altering blood vessel density, indicating that continued expression of VEGF may be required to promote tumor cell survival and maintain blood flow. While previous studies showed that MPA induces receptor activator of nuclear factor kappa-B ligand (RANKL) expression in rodent mammary gland, MPA reduced levels of RANKL in human tumor xenografts. RANKL levels remained suppressed in the presence of apigenin. Exposure of BT-474 cells to MPA in vitro also resulted in lower levels of RANKL; an effect that was independent of progesterone receptors since it occurred both in the presence and absence of the antiprogestin RU-486. In contrast to our in vivo observations, apigenin protected against MPA-dependent RANKL loss in vitro, suggesting that MPA and apigenin modulate RANKL levels differently in breast cancer cells in vivo and in vitro. These preclinical findings suggest that apigenin has potential as an agent for the treatment of progestin-dependent breast disease.

Mifepristone inhibits MPA-and FGF2-induced mammary tumor growth but not FGF2-induced mammary hyperplasia.

We have previously demonstrated a crosstalk between fibroblast growth factor 2 (FGF2) and progestins inducing experimental breast cancer growth. The aim of the present study was to compare the effects of FGF2 and of medroxyprogesterone acetate (MPA) on the mouse mammary glands and to investigate whether the antiprogestin RU486 was able to reverse the MPA- or FGF2-induced effects on both, mammary gland and tumor growth. We demonstrate that FGF2 administered locally induced an intraductal hyperplasia that was not reverted by RU486, suggesting that FGF2-induced effects are progesterone receptor (PR)-independent. However, MPA-induced paraductal hyperplasia was reverted by RU486 and a partial agonistic effect was observed in RU486-treated glands. Using C4-HD tumors which only grow in the presence of MPA, we showed that FGF2 administered intratumorally was able to stimulate tumor growth as MPA. The histology of FGF2-treated tumors showed different degrees of gland differentiation. RU486 inhibited both, MPA or FGF2 induced tumor growth. However, only complete regression was observed in MPA-treated tumors. Our results support the hypothesis that stromal FGF2 activates PR inducing hormone independent tumor growth.

Curcumin inhibits MPA-induced secretion of VEGF from T47-D human breast cancer cells.

OBJECTIVE: Recent clinical trials show that women who receive combined estrogen and progestin hormone therapy (HT) have a higher risk of breast cancer than women who receive estrogen alone or placebo. We have shown that progestins stimulate expression of vascular endothelial growth factor (VEGF), a potent angiogenic factor, in human breast cancer cells that express the progesterone receptors and mutant p53 protein. Because increased levels of VEGF promote tumor progression, compounds that prevent progestin-induced expression of VEGF could be clinically useful. The objective of this study was to examine whether the polyphenol compound curcumin has the capacity to block progestin-induced secretion of VEGF from T47-D human breast cancer cells. DESIGN: The estrogen and progesterone receptor containing T47-D human breast cancer cells was exposed to 10 nM progesterone or synthetic progestins and varying concentrations of curcumin to determine whether curcumin blocks progestin-dependent production of VEGF from tumor cells. RESULTS: Curcumin (0.001-10 microM for 18 h) reduced medroxyprogesterone acetate (MPA)-induced secretion of VEGF from T47-D cells in a dose-dependent manner. Secretion of VEGF from cells treated with progesterone or progestins other than MPA was unaffected by curcumin. CONCLUSIONS: MPA is the most widely used progestin in HT. Curcumin may therefore provide a clinically useful tool for the suppression of MPA-induced elaboration of VEGF by tumor cells. We propose therefore that clinical trials to assess the beneficial effects of curcumin in postmenopausal women are warranted.

Disparate effects of relaxin and TGFbeta1: relaxin increases, but TGFbeta1 inhibits, the relaxin receptor and the production of IGFBP-1 in human endometrial stromal/decidual cells.

BACKGROUND: The purpose of this study was to determine the effect of progestin, relaxin (RLX) and transforming growth factor beta1 (TGFbeta1) on the content of relaxin receptor (LGR7) mRNA. The effect of RLX on insulin-like growth factor binding protein-1 (IGFBP-1) production was determined to evaluate the biological function of RLX/receptor in human endometrial cells. METHODS AND RESULTS: The levels of LGR7 mRNA and the effect of hormones were determined by real-time PCR in endometrial cells. LGR7 mRNA was found to be relatively abundant in endometrial glands and decidual cells and much less in endometrial stromal cells. In stromal cells, medroxyprogesterone acetate (MPA), or MPA plus RLX, significantly increased the LGR7 mRNA and RLX alone had little effect. In decidual cells, RLX increased LGR7 mRNA in a dose- and time-dependent fashion. TGFbeta1 reduced the LGR7 mRNA. In stromal cells, MPA alone caused a slight increase (2-4-fold) of the production rate of IGFBP-1 whereas MPA plus RLX synergistically increased (>40-fold) the IGFBP-1 production. In decidual cells in which the basal production rate was already approximately 50-fold higher than in stromal cells, RLX alone caused an additional increase (>30-fold) on the production rate. TGFbeta1 inhibited the IGFBP-1 production. CONCLUSION: The present study showed that in undifferentiated endometrial stromal cells, progestin increases the RLX receptor content to enhance the effect of RLX on the target gene (IGFBP-1). In decidual cells, RLX alone up-regulates its receptor, resulting in a large scale induction of IGFBP-1. TGFbeta1 has an inhibitory effect on LGR7 and IGFBP-1.

Receptor density dictates the behavior of a subset of steroid ligands in glucocorticoid receptor-mediated transrepression.

By co-expressing glucocorticoid receptor (GR) and transcriptional reporter systems in GR-deficient Cos-7 cells, we profiled potency and efficacy of a panel of GR ligands as a function of GR expression levels (density). Our results show that potency and efficacy for GR full agonists, such as dexamethasone, in these transrepression assays are affected by receptor density. Intriguingly, receptor density dramatically influenced the behavior of the GR antagonist RU486 or the GR agonist medroxyprogesterone acetate (MPA). At high receptor density, both MPA and RU486 behaved as full agonists in transrepression: reducing GR density, however, resulted in conversion of these ligands from full agonist to full antagonists. In contrast, varying GR density could not convert cortisol and budesonide from GR agonists to antagonists. These results have clearly demonstrated, for the first time, an effect of receptor density on the agonist and antagonist properties of RU486 and MPA in GR-mediated transrepression.