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

Association between parity and pregnancy-associated tumor features in high-grade serous ovarian cancer

PURPOSE

High-grade serous ovarian cancer (HGSC) is the most common ovarian cancer subtype. Parity is an important risk-reducing factor, but the underlying mechanism behind the protective effect is unclear. Our aim was to study if the expression of hormones and proteins involved in pregnancy were affected by the woman's parity status, and if they may be associated with tumor stage and survival.

METHODS

We evaluated expression of progesterone receptor (PR), progesterone receptor membrane component 1 (PGRMC1), relaxin-2, and transforming growth factor beta 1 (TGFβ1) in tumor tissue from 92 women with HGSC parous (n = 73) and nulliparous (n = 19). Key findings were then evaluated in an independent expansion cohort of 49 patients. Survival rates by hormone/protein expression were illustrated using the Kaplan-Meier method. The independent prognostic value was tested by Cox regression, using models adjusted for established poor-prognostic factors (age at diagnosis, FIGO stage, type of surgery, and macroscopic residual tumor after surgery).

RESULTS

HGSC tumors from parous women were PR positive (≥ 1% PR expression in tumor cells) more often than tumors from nulliparous women (42% vs. 16%; p-value 0.04), and having more children was associated with developing PR positive tumors [i.e., ≥ 3 children versus nulliparity, adjusted for age at diagnosis and stage: OR 4.31 (95% CI 1.12-19.69)]. A similar result was seen in the expansion cohort. Parity status had no impact on expression of PGRMC1, relaxin-2 and TGFβ1. No associations were seen with tumor stage or survival.

CONCLUSION

Tumors from parous women with HGSC expressed PR more often than tumors from nulliparous women, indicating that pregnancies might possibly have a long-lasting impact on ovarian cancer development.

Toxicological Effects of Sewage Water on Chick Embryonic Development

For toxicity research, a total of 100 fertilized nonincubated eggs were used for this study. There were two trials in this experiment which were further divided into 2 phases based on a different days of sewage water treatment and observation days. In each trial, 50 eggs were used and divided into 5 groups. Group A, B, and C were treated with three different concentrations of pure and diluted sewage water (100%, 70%, and 30%), respectively. Control group D was given 0.3 ml saline solution (0.9% NaCl) and group E was uninjected. Different parameters such as the embryo's body weight, body length, forelimb length, hindlimb length, and head diameter were determined. In trial 1, eggs were treated with sewage water on 7th day of incubation and opened on 8th day (phase I) and 9th day (phase II). When the trial 1 (phase I) findings were compared to the control groups, it was observed that body weight, body length, forelimb length, and hindlimb length were highly statistically significant differences (p < 0.01), but the head diameter was not significant (p > 0.05). Phase II result showed embryo's head diameter was a highly statistically significant difference (p < 0.01), whereas forelimb length was significant (p < 0.05), and body weight, body length, and hindlimb length were nonsignificant (p > 0.05). In trial 2, eggs were treated with sewage water on 14th day of incubation and opened on 15th day (phase I) and 16th day (phase II). Results of 15th day showed a highly statistically significant (p < 0.01) difference in hindlimb length, while body weight, body length, forelimb length, and head diameter were nonsignificant (p > 0.05). Phase II of trial 2 showed that on 16th day, body weight, body length, forelimb length, hindlimb length, and head diameter showed a nonsignificant (p > 0.05) difference between experimental and control groups. Embryos were observed to be deforming on the 9th day (after 48 hours of exposure to sewage water). Other phases showed no signs of deformation. Except on 8th day of incubation, dose-related mortalities were present in experimental groups, while the control group showed no mortality.

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 (FT) in a manner similar to that described in human fallopian and ovarian cancer. In this study, we investigated the inhibitory effects of the progestin Depo-medroxyprogesterone acetate (DMPA) on FT carcinogenesis following treatment for 3 and 7 weeks in 5-week-old mogp-TAg mice. Overall, compared to vehicle-treated mice, the FT 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 (STICs) in the FT was significantly reduced in the DMPA (p<0.0005) treatment group. Moreover, the FT of the DMPA-treated mice developed significantly less adenocarcinoma compared to vehicle (p<0.005) at both treatment time points. DMPA treatment significantly induced cleaved caspase-3 (p<0.0005) in the FTE compared to vehicle suggesting that apoptosis is involved in DMPA-related clearance of abnormal cells from the FT. These data demonstrate that DMPA targets early events in FT carcinogenesis by clearing genetically damaged cells, leading to marked reduction in adenocarcinoma, supporting progestins as chemopreventives for FT and ovarian cancer.

A Review of Principal Studies on the Development and Treatment of Epithelial Ovarian Cancer in the Laying Hen Gallus gallus

Often referred to as the silent killer, ovarian cancer is the most lethal gynecologic malignancy. This disease rarely shows any physical symptoms until late stages and no known biomarkers are available for early detection. Because ovarian cancer is rarely detected early, the physiology behind the initiation, progression, treatment, and prevention of this disease remains largely unclear. Over the past 2 decades, the laying hen has emerged as a model that naturally develops epithelial ovarian cancer that is both pathologically and histologically similar to that of the human form of the disease. Different molecular signatures found in human ovarian cancer have also been identified in chicken ovarian cancer including increased CA125 and elevated E-cadherin expression, among others. Chemoprevention studies conducted in this model have shown that decreased ovulation and inflammation are associated with decreased incidence of ovarian cancer development. The purpose of this article is to review the major studies performed in laying hen model of ovarian cancer and discuss how these studies shape our current understanding of the pathophysiology, prevention, and treatment of epithelial ovarian cancer.

What are the mechanisms of action of the different contraceptive methods to reduce the risk of ovarian cancer?

OBJECTIVE

Ovarian cancer (OvCa) is the deadliest gynaecologic malignancy. Knowing that OvCa, as a disease, has different origins has allowed us to relate them to the mechanisms of action of different contraceptive methods with the aim of evaluating the possibility of their use in reducing risk.

STUDY DESIGN

This commentary review article will instead focus on the recent findings on the role of contraceptive methods in preventing of OvCa.

RESULTS

Combined hormonal contraceptive (CHC) use is an effective method of chemoprevention for OvCa in the general population and in women with genetic disorders. Salpingectomy, better than tubal ligation, should be offered for ovarian/tubal/peritoneal cancer prevention. Progestogen-only methods can decrease the risk of OvCa via reduced menstrual bleeding and by changes in the hormonal environment that surrounds the ovary. IUDs of any type, through different mechanisms, decrease the risk of OvCa. Barrier methods prevent the passage of germs into the tubes and ovaries and the inflammatory state they produce.

CONCLUSIONS

Most contraceptive methods have a mechanism of action that may favour a reduction in the risk of OvCa. The theories of incessant ovulation, retrograde menstruation, and that the fallopian tubes are the site of origin of a proportion of high-grade serous OvCa, have led to the recommendation that anovulatory methods, those that decrease menstrual bleeding, and those that blocked tubes, or even better, 'opportunistic salpingectomy' are a current approach to prevent OvCa in the population general and, above all, in the population at risk.

The chicken model organism for epigenomic research

The chicken model organism has advanced the areas of developmental biology, virology, immunology, oncology, epigenetic regulation of gene expression, conservation biology, and genomics of domestication. Further, the chicken model organism has aided in our understanding of human disease. Through the recent advances in high-throughput sequencing and bioinformatic tools, researchers have successfully identified sequences in the chicken genome that have human orthologs, improving mammalian genome annotation. In this review, we highlight the importance of chicken as an animal model in basic and pre-clinical research. We will present the importance of chicken in poultry epigenetics and in genomic studies that trace back to their ancestor, the last link between human and chicken in the tree of life. There are still many genes of unknown function in the chicken genome yet to be characterized. By taking advantage of recent sequencing technologies, it is possible to gain further insight into the chicken epigenome.

Phase II Trial of Chemopreventive Effects of Levonorgestrel on Ovarian and Fallopian Tube Epithelium in Women at High Risk for Ovarian Cancer: An NRG Oncology Group/GOG Study

A large body of epidemiologic evidence has shown that use of progestin-containing preparations lowers ovarian cancer risk. The purpose of the current study was to gather further preclinical evidence supporting progestins as cancer chemopreventives by demonstrating progestin-activation of surrogate endpoint biomarkers pertinent to cancer prevention in the genital tract of women at increased risk of ovarian cancer. There were 64 women enrolled in a multi-institutional randomized trial who chose to undergo risk-reducing bilateral salpingo-oophorectomy (BSO) and to receive the progestin levonorgestrel or placebo for 4 to 6 weeks prior to undergoing BSO. The ovarian and fallopian tube epithelia (FTE) were compared immunohistochemically for effects of levonorgestrel on apoptosis (primary endpoint). Secondary endpoints included TGFβ isoform expression, proliferation, and karyometric features of nuclear abnormality. In both the ovary and fallopian tube, levonorgestrel did not confer significant changes in apoptosis or expression of the TGFβ1, 2, or 3 isoforms. In the ovarian epithelium, treatment with levonorgestrel significantly decreased the proliferation index. The mean ovarian Ki-67 value in the placebo arm was 2.027 per 100 cells versus 0.775 per 100 cells in the levonorgestrel arm (two-sided P value via Mann-Whitney U test = 0.0114). The karyometric signature of nuclei in both the ovarian and FTE deviated significantly from normal controls (women at average risk of ovarian cancer), but was significantly less abnormal in women treated with levonorgestrel. These karyometric data further support the idea that progestins may clear genetically abnormal cells and act as chemopreventive agents against ovarian and fallopian tube cancer.

The role of menopausal hormone therapy in women with or at risk of ovarian and breast cancers: Misconceptions and current directions

For women who are candidates for menopausal hormone therapy (MHT), estrogen can provide relief from symptomatic menopause, decrease rates of chronic illnesses, and improve health-related quality of life. However, confusion surrounds the evidence regarding the impact of exogenous estrogen and progesterone on the breast and ovary. Available data regarding the risks of MHT (estrogen and/or progestin) related to the development of breast and ovarian cancer are often inconsistent or incomplete. Modern molecular and genetic techniques have improved our understanding of the heterogeneity of breast and ovarian cancer. This enhanced understanding of the disease has impacted our understanding of carcinogenesis. Treatment options have evolved to be more targeted toward hormonal therapy for certain subtypes of disease, whereas cytotoxic chemotherapy remains the standard for other histological and molecular subtypes. The role of MHT in the breast and ovarian cancer survivor, as well as women who are at high risk for the development of hereditary breast and ovarian cancer, remains controversial despite evidence that this treatment can improve quality of life and survival outcomes. Through this article, we examine the evidence for and against the use of MHT with a focus on women who have or are at high risk for breast and ovarian cancer.

Preterm delivery is associated with an increased risk of epithelial ovarian cancer among parous women

Epithelial ovarian cancer is a fatal disease of largely unknown etiology. Higher parity is associated with reduced risk of ovarian cancer. However, among parous women, the impact of pregnancy-related factors on risk is not well understood. This population-based case-control study included all parous women with epithelial ovarian cancer in Denmark, Finland, Norway and Sweden during 1967-2013 (n = 10,957) and up to 10 matched controls (n = 107,864). We used conditional logistic regression to estimate odds ratios (ORs) with 95% confidence intervals (CIs) for pregnancy-related factors and ovarian cancer risk by histological subtype. Preterm delivery was associated with an increased risk [pregnancy length (last pregnancy) ≤30 vs. 39-41 weeks, OR 1.33 (95% CI 1.06-1.67), adjusted for number of births]; the OR increased as pregnancy length decreased (p for trend < 0.001). Older age at first and last birth was associated with a decreased risk [first birth: 30-39 vs. <25 years: adjusted OR 0.76 (95% CI 0.70-0.83); last birth 30-39 vs. <25 years: adjusted OR 0.76 (95% CI 0.71-0.82)]. Increasing number of births was protective [≥4 births vs. 1; OR 0.63 (95% CI 0.59-0.68)] for all subtypes, most pronounced for clear-cell tumors [OR 0.30, (95% CI 0.21-0.44), p_{heterogeneity}  < 0.001]. No associations were observed for multiple pregnancies, preeclampsia or offspring size. In conclusion, in addition to high parity, full-term pregnancies and pregnancies at older ages were associated with decreased risk of ovarian cancer. Our findings favor the cell clearance hypothesis, i.e. a recent pregnancy provides protection by clearing of precancerous cells from the epithelium of the ovary/fallopian tubes, mediated by placental or ovarian hormones.

Ovarian Cancer Prevention in High-risk Women

Ovarian carcinoma is the most lethal malignancy of the female genital tract. Population-based trials in the general population have not demonstrated that screening improves early detection or survival. Therefore, application of prevention strategies is vital to improving outcomes from this disease. Surgical prevention reduces risk and prophylactic risk-reducing salpingo-oophorectomy is the most effective means to prevent ovarian carcinoma in the high-risk patient although the risks do not outweigh the benefits in average risk patients. Other surgical and medical options have unknown or limited efficacy in the high-risk patient. In this review, we define the patient at high risk for ovarian cancer, discuss how to identify these women and weigh their available ovarian cancer prevention strategies.

Chemoprevention of spontaneous ovarian cancer in the domestic hen

The hen is an attractive animal model for in vivo testing of agents that thwart ovarian carcinogenesis because ovarian cancer in the domestic hen features clinical and molecular alterations that are similar to ovarian cancer in humans, including a high incidence of p53 mutations. The objective of the study was to test the potential ovarian cancer chemopreventive effect of the p53 stabilizing compound CP-31398 on hens that spontaneously present the ovarian cancer phenotype. Beginning at 79 wk of age, 576 egg-laying hens (Gallus domesticus) were randomized to diets containing different amounts of CP-31398 for 94 wk, 5 d, comprising a control group (C) (n = 144), which was fed a diet containing 0 ppm (mg/kg) of CP-31398; a low-dose treatment (LDT) group (n = 144), which was fed a diet containing 100 ppm of CP-31398; a moderate-dose treatment (MDT) group (n = 144) which was fed a diet containing 200 ppm of CP-31398; and a high-dose treatment (HDT) group (n = 144), which was fed a diet containing 300 ppm of CP-31398. Hens were killed at 174 wk of age to determine the incidence of ovarian and oviductal adenocarcinomas. Whereas the incidence of localized and metastatic ovarian cancers in the MDT and HDT groups was significantly lower (up to 77%) compared to levels in the C and LDT groups (P < 0.05), the incidence of oviductal cancer was unaffected by CP-31398. CP-31398 appears to be an effective tool for chemoprevention against ovarian malignancies, but does not appear to affect oviductal malignancies.

Progestins inhibit calcitriol-induced CYP24A1 and synergistically inhibit ovarian cancer cell viability: An opportunity for chemoprevention

OBJECTIVES

Previously we have shown in endometrial cells that progesterone (P4) and calcitriol (CAL, 1,25(OH)2D3) synergistically promote apoptosis and that progestins induce expression of the vitamin D receptor. In the current study we examined the progestin/vitamin D combination in ovarian cells and searched for other progestin-related effects on vitamin D metabolism that may underlie the novel interaction between progestins and vitamin D, including whether progestins inhibit CYP24A1, the enzyme that renders CAL inactive.

METHODS

We investigated the impact of P4 on CAL-induced CYP24A1 expression in cancer cell lines expressing progesterone receptors (PRs), [OVCAR-5, OVCAR-3-PGR (PR-transfected OVCAR-3 ovarian line), and T47D-WT, T47D-A and T47D-B (breast lines expressing PRs or individual PR isoforms)] or lines that do not express PRs (OVCAR-3 and T47D-Y). We examined CYP24A1 expression using RT-PCR and western blotting, and apoptosis by TUNEL. We also investigated P4 inhibition of Cyp24a1 in ovaries from CAL-treated mice.

RESULTS

CAL treatment induced CYP24A1 expression. When co-treated with P4, cell lines expressing PRs showed marked inhibition of CYP24A1 expression (p<0.001), along with increased apoptosis (p<0.01); cells not expressing PRs did not. Mouse ovaries showed a significant reduction in CAL-induced Cyp24a1 mRNA (p<0.001) and protein (p<0.01) in response to P4.

CONCLUSIONS

We show for the first time that progestins and vitamin D synergistically reduce cell viability and induce apoptosis in ovarian cells and that progestins PR-dependently inhibit CAL-induced CYP24A1, thus extending CAL activity. The combination of progestins and vitamin D deserves further consideration as a strategy for inhibiting ovarian carcinogenesis.

The role of reproductive hormones in epithelial ovarian carcinogenesis

Epithelial ovarian cancer comprises ∼85% of all ovarian cancer cases. Despite acceptance regarding the influence of reproductive hormones on ovarian cancer risk and considerable advances in the understanding of epithelial ovarian carcinogenesis on a molecular level, complete understanding of the biologic processes underlying malignant transformation of ovarian surface epithelium is lacking. Various hypotheses have been proposed over the past several decades to explain the etiology of the disease. The role of reproductive hormones in epithelial ovarian carcinogenesis remains a key topic of research. Primary questions in the field of ovarian cancer biology center on its developmental cell of origin, the positive and negative effects of each class of hormones on ovarian cancer initiation and progression, and the role of the immune system in the ovarian cancer microenvironment. The development of the female reproductive tract is dictated by the hormonal milieu during embryogenesis. Intensive research efforts have revealed that ovarian cancer is a heterogenous disease that may develop from multiple extra-ovarian tissues, including both Müllerian (fallopian tubes, endometrium) and non-Müllerian structures (gastrointestinal tissue), contributing to its heterogeneity and distinct histologic subtypes. The mechanism underlying ovarian localization, however, remains unclear. Here, we discuss the role of reproductive hormones in influencing the immune system and tipping the balance against or in favor of developing ovarian cancer. We comment on animal models that are critical for experimentally validating existing hypotheses in key areas of endocrine research and useful for preclinical drug development. Finally, we address emerging therapeutic trends directed against ovarian cancer.

The chicken model of spontaneous ovarian cancer

The chicken is a unique experimental model for studying the spontaneous onset and progression of ovarian cancer (OVC). The prevalence of OVC in chickens can range from 5 to 35% depending on age, genetic strain, reproductive history, and diet. Furthermore, the chicken presents epidemiological, morphological, and molecular traits that are similar to human OVC making it a relevant experimental model for translation research. Similarities to humans include associated increased risk of OVC with the number of ovulations, common histopathological subtypes including high-grade serous, and molecular-level markers or pathways such as CA-125 expression and p53 mutation frequency.  Collectively, the similarities between chicken and human OVC combined with a tightly controlled genetic background and predictable onset window provides an outstanding experimental model for studying the early events and progression of spontaneous OVC tumors under controlled environmental conditions. This review will cover the existing literature on OVC in the chicken and highlight potential opportunities for further exploitation (e.g. biomarkers, prevention, treatment, and genomics).