Nonsteroidal antiinflammatory drugs and progestins synergistically enhance cell death in ovarian epithelial cells.

OBJECTIVE: There is growing evidence that progestins and nonsteroidal antiinflammatory drugs (NSAIDs) may prevent ovarian cancer. Because both induce apoptosis, we investigated the potential for synergistic impact of combined drug treatment on cell death. STUDY DESIGN: Using normal and malignant human ovarian epithelial cells and an NSAID-sensitive human colon cancer cell line, we evaluated the effects of progestins and NSAIDs alone and in combination on apoptosis. RESULTS: Both progestins and NSAIDs dose dependently inhibited cell growth (P < .0001). Doses of NSAIDs or progestins that independently reduced cell viability by less than 30% synergistically reduced cell viability by 70-95% when combined. Similarly, the NSAID/progestin combination conferred 4- to 18-fold (P < .05) increased apoptosis over either treatment alone. CONCLUSION: Our results suggest it may be possible to combine progestins and NSAIDs to achieve ovarian cancer prevention at lower doses of each than are required for single administration, thereby lessening the risk of side effects posed by these agents.

Progestin Significantly Inhibits Carcinogenesis in the Mogp-TAg Transgenic Mouse Model of Fallopian Tube Cancer.

Recent studies suggest that the fallopian tube epithelium (FTE) harbors the precursor for high-grade ovarian cancer, creating opportunities for targeting the FTE for ovarian cancer prevention. Preclinical evidence supports progestins as ovarian cancer preventives, but the effect of progestins on the FTE is not well characterized. The murine oviduct-specific glycoprotein promotor-driven simian virus 40 large T-Antigen (mogp-TAg) transgenic mouse model develops neoplastic lesions in the fallopian tube in a manner similar to that described in human fallopian tube and ovarian cancers. In this study, we investigated the inhibitory effects of the progestin depo-medroxyprogesterone acetate (DMPA) on fallopian tube carcinogenesis following treatment for 3 and 7 weeks in 5-week-old mogp-TAg mice. Overall, compared with vehicle-treated mice, the fallopian tube of DMPA-treated mice was significantly smaller (P < 0.0005), accumulated fewer p53-positive cells, had normal distribution of ciliated cells, less nuclear pleomorphism and epithelial tufting, and had a significantly lower proliferative index (P = 0.001). Accumulation of p53 signatures and serous tubal intraepithelial carcinomas (STIC) in the fallopian tube was significantly reduced in the DMPA (P < 0.0005) treatment group. Moreover, the fallopian tube of the DMPA-treated mice developed significantly less adenocarcinoma compared with vehicle (P < 0.005) at both treatment time points. DMPA treatment significantly induced cleaved caspase-3 (P < 0.0005) in the FTE compared with vehicle suggesting that apoptosis is involved in DMPA-related clearance of abnormal cells from the fallopian tube. These data demonstrate that DMPA targets early events in fallopian tube carcinogenesis by clearing genetically damaged cells, leading to marked reduction in adenocarcinoma, supporting progestins as chemopreventive agents for fallopian tube and ovarian cancers. PREVENTION RELEVANCE: The fallopian tube is thought to harbor the cell of origin for most ovarian cancers. We show in a mouse model of fallopian tube cancer that progestin eradicates the earliest known precancerous lesions and markedly inhibits fallopian tube carcinogenesis, adding to growing preclinical evidence supporting progestins as potent ovarian cancer chemopreventive agents.

Progestin treatment induces apoptosis and modulates transforming growth factor-beta in the uterine endometrium.

BACKGROUND: Epidemiologic, animal, and human data suggest that progestins are potent endometrial cancer preventive agents. In the ovarian surface epithelium, progestins have been hypothesized to confer a cancer preventive effect via apoptosis and modulation of transforming growth factor-beta (TGF-beta). Given that the ovarian epithelium and endometrium share a common embryologic origin and similar reproductive and hormonal risk factors for malignancy, we tested the hypothesis that progestins confer biological effects in the endometrium similar to those in the ovary. METHODS: Postmenopausal female macaques (n = 78) were randomized into four groups to receive a diet for 36 months containing no hormone versus conjugated equine estrogen (CEE), medroxyprogesterone acetate (MPA), or CEE + MPA. The endometrium was then examined immunohistochemically for treatment-specific changes using antibodies to activated caspase-3 (for apoptosis), Ki-67 (proliferation), and the TGF-beta1, TGF-beta2, and TGF-beta3 isoforms. RESULTS: Percentages of caspase-positive endometrial glandular cells were 3- to 5-fold higher in CEE + MPA-treated animals compared with all others (P < 0.05). Caspase-expressing cells were six times more numerous in the endometrial stroma of animals treated with MPA alone relative to other groups (P < 0.0001). Induction of endometrial glandular cell apoptosis in the CEE + MPA-treated group was associated with a dramatic increase in expression of TGF-beta2 and TGF-beta3 in the stromal compartment of the endometrium (P < 0.0001). CONCLUSION: Progestin treatment activates chemopreventive biological effects in the endometrium that are similar to those in the ovarian surface epithelium. These data may facilitate identification of a chemopreventive approach that dramatically lessens the risk of both uterine and ovarian cancer.

Evidence of a chemopreventive effect of progestin unrelated to ovulation on reproductive tract cancers in the egg-laying hen.

Epidemiologic, laboratory, and animal evidence suggests that progestins and vitamin D may be potent ovarian cancer preventives. Our objectives were to evaluate progestins as reproductive tract cancer chemopreventives in the chicken, determine whether restricted ovulation affected the incidence of reproductive tract tumors, and assess whether vitamin D would confer cancer protection either alone or in addition to progestin. A total of 2,400 two-year-old Single Comb White Leghorns were randomized into six groups (400 each) with hormonal and dietary manipulation for 2 years as follows: (i) no intervention, regular feed/caloric intake, (ii) control, (iii) vitamin D, (iv) the progestin levonorgestrel, (v) vitamin D plus levonorgestrel, and (vi) the progestin Provera (medroxyprogesterone acetate). Groups 2 to 6 were caloric restricted to inhibit ovulation. Our results indicated that caloric restriction decreased egg production by more than 60%, and was associated with a greater than 70% decrease in reproductive tract cancers. Ovulatory events did not differ among the caloric-restricted groups (groups 2-6), except for the group receiving levonorgestrel, which had fewer ovulatory events than controls (P = 0.046). After correcting for egg production, birds receiving progestins had significantly fewer reproductive tract cancers [OR, 0.61; confidence interval (CI), 0.39-0.95; P = 0.03], with similar proportionate reductions in tumors arising in either the ovary or oviduct. Vitamin D did not significantly affect cancer incidence overall, or add to the cancer preventive effect of progestins. This study suggests a protective effect of progestins against ovarian and oviductal cancers. These data support the concept that progestins provide a chemopreventive effect unrelated to ovulation.

Progesterone enhances calcitriol antitumor activity by upregulating vitamin D receptor expression and promoting apoptosis in endometrial cancer cells.

Human studies suggest that progesterone and calcitriol may prove beneficial in preventing or inhibiting oncogenesis, but the underlying mechanism is not fully understood. The current study investigates the effects of progesterone, calcitriol, and their combination on immortalized human endometrial epithelial cells and endometrial cancer cells and identifies their targets of action. Combination treatment with both agents enhanced vitamin D receptor expression and inhibited cell proliferation through caspase-3 activation and induction of G0-G1 cell-cycle arrest with associated downregulation of cyclins D1 and D3 and p27 induction. We used mass spectrometry-based proteomics to measure protein abundance differences between calcitriol-, progesterone-, or combination-exposed endometrial cells. A total of 117 proteins showed differential expression among these three treatments. Four proteins were then selected for validation studies: histone H1.4 (HIST1H1E), histidine triad nucleotide-binding protein 2 (HINT2), IFN-induced, double-stranded RNA-activated protein kinase (EIF2AK2), and Bcl-2-associated X protein (BAX). Abundance levels of selected candidates were low in endometrial cancer cell lines versus the immortalized endometrial epithelial cell line. All four proteins displayed elevated expression in cancer cells upon exposure to calcitriol, progesterone, or the combination. Further BAX analysis through gain- or loss-of-function experiments revealed that upregulation of BAX decreased cell proliferation by changing the BAX:BCL-2 ratio. Knockdown of BAX attenuated progesterone- and calcitriol-induced cell growth inhibition. Our results showed that progesterone and calcitriol upregulate the expression of BAX along with other apoptosis-related proteins, which induce inhibition of endometrial cancer cell growth by apoptosis and cell-cycle arrest.

Effects of receptor tyrosine kinase inhibitor A47 on estrogen and growth factor-dependent breast cancer cell proliferation and apoptosis in vitro.

BACKGROUND AND OBJECTIVES: We propose that a growth factor receptor tyrosine kinase (RTK) inhibitor, such as tyrphostin A47, could serve as an adjunct to estrogen replacement therapy (ERT) for postmenopausal breast cancer survivors. Tyrphostins have been shown to block estrogen (E2)-induced proliferation in the human breast cancer MCF-7 cell line. Therefore, the effects of A47 on signal transduction, cell cycle progression, and apoptosis in E2-mediated breast cancer cell growth in vitro were investigated. METHODS: Cell growth was determined by MTT proliferation assay, cell cycle analysis assessed by flow cytometry, and RTK activation by Western blot. Apoptosis assays included nuclear staining, TdT-mediated dUTP-X nick end labeling, and caspase 3 activation. RESULTS: We find A47 selectively inhibits epidermal growth factor (EGF) and basic fibroblast growth factor but not insulin growth factor-1 proliferation. Although A47 inhibits EGF-induced phosphorylation of the EGF receptor in A431 cells, it does not consistently block MAP kinase phosphorylation. CONCLUSIONS: Taken together, A47 blocks E2/EGF-induced activation of EGFR and therefore interferes with the proximal EGFR signaling pathway. A47 also arrests the cells at the G1-S transition of the cell cycle and induces cell death by apoptosis. Thus, a growth factor RTK may be useful in blocking hormone-dependent tumor growth in an elevated E2 environment.