Metaplastic potential of p53 down-regulation in ovarian surface epithelial cells affected by ovulation

Women who deliver twins are more likely to smoke and have high frequencies of specific SNPs: Results from a sample of African-American women who delivered preterm, low birth weight babies

OBJECTIVES

We examine if there are genetic and environmental differences between mothers of singleton and multiple pregnancies in a sample of African-American mothers.

METHODS

We focus on genomic areas suggested to increase or decrease the odds of multiple pregnancies. We computed the odds ratio (OR) and the 95% confidence interval (CI) for each SNP unadjusted or adjusted with smoking. SNPs' allelic differences between mothers of multiple pregnancies and singletons were also tested using Fisher's exact test. We considered additive terms for the SNPs' genotypes, smoking, and a multiplicative interaction term of two selected SNPs' genotypes.

RESULTS

We found significant interactions between smoking and SNPs of the CYP19A, MDM4, MTHFR and TP53 genes which correlated with higher odds of twinning. We also found a significant interaction between SNPs at the TP53 (rs8079544) and MTHFR gene (rs4846049), where the interaction between the homozygotes (TT for rs8079544, GG for rs4846049) correlated with lowered odds of multiple pregnancy.

CONCLUSIONS

We provide a mechanistic explanation and preliminary evidence for previous reports that mothers of twins are more likely to have smoked, despite seemingly conflicting evidence for the fertility-reducing effects of nicotine. Nicotine, as an aromatase inhibitor, inhibits estrogen synthesis and may allow for greater production of gonadotropins. While smoking may have deleterious effects on fertility across many genotypes, in women of specific genotypes it may raise their odds of producing twins. TP53 involvement suggests the necessity of future work examining relationships between women who bear multiples and cancer risk.

Ovarian morphometrics in TP53-deficient mice

The objective of these investigations was to characterize ovarian responses to hormonal stimulation in TP53-deficient mice. TP53-deficient (KO) and wild-type (WT) mice were induced to ovulate with pregnant mare serum gonadotropin followed by human chorionic gonadotropin. Effect of estradiol on ovarian morphology was determined in induced and control mice implanted with estradiol-containing or placebo pellets. Blood was collected and mice were killed 7 days following implantation. Preserved ovaries were serially sectioned and stained. Numbers of follicles (all classifications) decreased with ovulation induction, but did not differ between WT and KO mice. Numbers of corpora lutea (CL) were less in ovulation-induced KO mice treated with estradiol compared to WT mice. Area of individual CL and serum concentrations of progesterone were greater in ovulation-induced KO mice given estradiol compared to WT mice. Ovulation-induced KO mice had more, larger hemorrhagic follicles than similarly treated WT mice, but hemorrhagic follicles were not influenced by estradiol. Proliferation of ovarian surface epithelial cells did not differ between KO and WT mice induced to ovulate and given estradiol. Ovaries from TP53 gene knockout mice (n = 4) induced to ovulate and given a 21-day estradiol implant three times over 58 days were observed for precursor lesions. There was no indication of precursor lesions in any TP53 KO or WT mouse. TP53 status did not influence recruitment of follicles, but TP53 deficiency hindered the ability of human chorionic gonadotropin to cause ovulation.

Gonadotropin-induced superovulation drives ovarian surface epithelia proliferation in CD1 mice

The ovarian surface epithelium (OSE) is a monolayer of cells that surround the ovary and accommodate repeated tear and repair in response to ovulation. OSE cells are thought to be the progenitors of 90% of ovarian cancers. Currently, the total amount of proliferation of the OSE has not been reported in response to one ovulatory event. In this study, proliferation of the OSE was quantified in response to superovulation induced by ip injection of pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG) in immature 27-d-old CD1 mice using bromodeoxyuridine (BrdU). BrdU incorporation into the OSE cells was measured from the time of hCG injection for a total cumulative label of 12 h. BrdU incorporation was also measured from the time of PMSG injection for a total label of 60 h to correlate proliferation with specific gonadotropin stimulation. The OSE proliferation was significantly higher in superovulated animals compared with control mice at all time points. Proliferation was also analyzed in discrete anatomical sections and indicated that OSE covering antral follicles and corpora lutea proliferated more rapidly than OSE distal to follicular growth. Finally, apoptosis was assessed in response to ovulation, and virtually no cell death within the OSE was detected. These data demonstrate that the OSE, especially near antral follicles and corpora lutea, proliferates significantly in response to the gonadotropins PMSG and hCG. Therefore, ovarian surface cell division in response to ovulation could contribute to ovarian cancer by proliferation-induced DNA mutations and transformed cell progression.

Carcinogenic potential of ovulatory genotoxicity

Ovulation is a rate-limiting event for the perpetuation of a species; unfortunately, it imparts a cancer risk. Reactive oxidants generated during the mechanics of ovulatory follicular rupture damage the DNA of ovarian surface epithelial cells that are located within a limited diffusion radius. Those cells that survive the trauma of ovulation, along the margins of a ruptured follicle, proliferate and migrate to reconcile the discontinuity within the ovarian epithelium created at the site of oocyte release. It is conceivable that clonal expansion of an ovarian surface epithelial cell with unrepaired DNA, but not committed to death, could be an initiating factor in the etiology of common ovarian cancer. In fact, the majority of cancers of the ovary are derived from the surface epithelium; and circumstances that avert ovulation (oral contraceptive use, pregnancy/lactation) protect against ovarian adenocarcinoma. Not surprisingly, the genotoxic potential of ovulation is exacerbated by malfunctions in tumor suppressor/cell-cycle arrest and base-excision repair mechanisms. Recent experimental evidence indicates that vitamin E and progesterone protect against ovarian metaplasia by negating the oxidative stress of ovulation and by enhancing the repair capacity (genomic integrity) of the surface epithelium, respectively. Ovarian cancer of surface epithelial origin is a deadly insidious disease because it characteristically remains asymptomatic until it has metastasized throughout the abdominal cavity; therefore, prevention is a high priority.

Endometriotic Cells Exhibit Metaplastic Change and Oxidative DNA Damage as Well as Decreased Function, Compared to Normal Endometrium

A widely accepted theory of the etiology of endometriosis is that it originates from the implantation and invasion of cells from retrograde menstruation to various sites in the body particularly the pelvic peritoneal cavity. Little is known of the function of these cells in ectopic sites. Normal endometrium was compared with endometriotic tissue using an antibody to Placental Cadherin (P Cadherin), a recently studied cadherin that is implicated in metaplasia and early neoplasia and also 8-hydroxyguanine, an indicator of oxidative DNA damage. Comparisons of endometrial tissue function were made using expression of transforming growth factor beta-1 (TGFbeta-1) and insulin-like growth factor-I (IGF-I). There was no labelling for anti-P Cadherin or anti-8-hydroxydeoxyguanosine in normal endometrium but marked labelling for both on the apical surface of the endometriotic epithelium. Studies of markers of normal endometrial function were all de-expressed in endometriosis. This study indicates that endometriosis cells are abnormal and exhibit oxidative DNA damage, metaplasia and markedly reduced function compared to normal endometrium.

Intraperitoneal serous adenocarcinoma: a critical appraisal of three hypotheses on its cause

OBJECTIVE

Serous ovarian, Fallopian tube, and peritoneal adenocarcinomas are remarkably similar, both in their morphology, as well as in their clinical behavior. Despite extensive clinical and fundamental research, controversy still exists on the origin of serous female adnexal tumors. Difficulties in identification of site of origin at late stage the of disease at detection, when ovary, Fallopian tube, and the abdominal cavity are usually all involved, in addition to their macroscopic and microscopic resemblance, are major causes of this debate. In 3 hypotheses, 3 possible tissues of origin are proposed: the ovarian surface epithelium, the Fallopian tube epithelium, and the secondary Mullerian system.

STUDY DESIGN

We searched for all peer-reviewed articles and reviews that examined "serous ovarian carcinoma," "Fallopian tube carcinoma," "Mullerian system," "ovarian surface epithelium," "tubal epithelium," and "peritoneal." We included only articles that could give information on the origin of serous carcinomas. Additional articles were added by examining references of overview articles in relevant fields.

RESULTS

Discussed are the experimental data underlying these hypotheses.

CONCLUSION

An attempt is made to integrate the 3 hypotheses into a comprehensive model of serous intraperitoneal adenocarcinogenesis. It can be concluded that the Fallopian tubes play a major role in the development of female serous cancer.

Oxidative damage to DNA of ovarian surface epithelial cells affected by ovulation: carcinogenic implication and chemoprevention

The majority of cancers of the ovary are thought to originate from a surface epithelial cell perturbed by ovulation. Outgrowth of a follicle destined to ovulate brings it into apposition with the ovarian epithelium. Ovarian surface cells are consequently exposed, within a limited diffusion radius, to inflammatory agents and reactive oxidants generated during periovulatory processes. Cells that overlie the formative site of follicular rupture suffer irreparable damages and undergo apoptosis. Potentially mutagenic 8-oxoguanine modifications were detected in (surviving) cells circumjacent to postovulatory ovine and human follicles. It is conceivable that clonal expansion of a cell with unrepaired DNA, but not committed to death, could be an initiating factor in the etiology of malignancy, insofar as proliferative ovulatory wound-repair responses may propagate mutations. Since the prognosis for ovarian cancer patients with invasive disease is so poor, and early detection has proven elusive, it is imperative that prospective methods of chemo-prevention be explored. Ovulation-induced oxidative base damages to the ovarian epithelium of ewes were prevented by vitamin E. Oxoguanine adducts persisted and CA-125 (a phenotype of metaplastic transformation) was expressed in cultures of cells that were distressed by ovulation in which p53 synthesis was inhibited. Vitamin E negated this reaction. Ovarian cyclicity and fertility were not altered in vitamin-treated ewes. A prophylactic benefit of a supplemental antioxidant is suggested in "ovulating" individuals designated at risk (e.g., due to a tumor suppressor malfunction) for the development of ovarian cancer.