Strong Cumulative Evidence of Associations of 6 Single Nucleotide Polymorphisms with Ovarian Cancer Risk: An Umbrella Review

Background: An increasing number of studies have reported associations between single nucleotide polymorphisms (SNPs) and ovarian cancer (OC) risk. However, some of the findings were inconsistent. The objective of this umbrella review was to evaluate the associations comprehensively and quantitatively. Methods: The protocol of this review was registered in PROSPERO (No. CRD42022332222). We searched the PubMed, Web of Science, and Embase databases to identify related systematic reviews and meta-analyses from inception to 15 October 2021. In addition to estimating the summary effect size by using fixed and random effects models and calculating the 95% prediction interval, we evaluated the cumulative evidence for associations with nominally statistical significance based on the Venice criteria and false positive report probability (FPRP). Results: Forty articles were included in this umbrella review, which referred to a total of 54 SNPs. The median number of original studies per meta-analysis was four, while the median number of total subjects was 3455. All included articles had greater than moderate methodological quality. A total of 18 SNPs were nominally statistically associated with OC risk; 6 SNPs (8 genetic models), 5 SNPs (7 genetic models), and 16 SNPs (25 genetic models) were identified as strong, moderate, and weak cumulative evidence, respectively. Conclusion: This umbrella review revealed associations between SNPs and OC risk and suggested strong cumulative evidence of associations of six SNPs (eight genetic models) with OC risk.

Characterization and Activation of Fas Ligand-Producing Mouse B Cells and Their Killer Exosomes

B lymphocytes make several contributions to immune regulation including production of antibodies with regulatory properties, release of immune suppressive cytokines, and expression of death-inducing ligands. A role for Fas ligand (FasL)-expressing "killer" B cells in regulating T helper (T_H) cell survival and chronic inflammation has been demonstrated in animal models of schistosome worm and other infections, asthma, autoimmune arthritis, and type 1 diabetes. FasL⁺ B cells were also capable of inducing immune tolerance in a male-to-female transplantation model. Interestingly, populations of B cells found in the spleen and lungs of naïve mice constitutively expresses FasL and have potent killer function against T_H cells that is antigen-specific and FasL-dependent. Epstein-Barr virus-transformed human B cells constitutively express FasL and package it into exosomes that co-express MHC Class II molecules and have killer function against antigen-specific T_H cells. FasL⁺ exosomes with markers of B-cell lineage are abundant in the spleen of naïve mice. Killer B cells therefore represent a novel target for immune modulation in many disease settings. Our laboratory has published methods of characterizing FasL⁺ B cells and inducing their proliferation in vitro. This updated chapter will describe methods of identifying and expanding killer B cells from mice, detecting FasL expression in B cells, extracting FasL⁺ exosomes from spleen and culture supernatants, and performing functional killing assays against antigen-specific T_H cells.

Long-term apoptosis-related protein expression in the diabetic mouse ovary

Emerging evidence has shown that oocytes from diabetic ovaries exhibit delayed maturation, mitochondrial dysfunction and meiotic defects, which are related increased apoptosis. The main objective of the present study was to analyze the apoptosis pathways activated during follicular loss at multiple time points in a diabetic mouse model. Twenty BALB/c mice were used in this study, and diabetes mellitus was induced by streptozotocin injection. Three diabetic and two control animals were sacrificed on days 15, 20, 70 and 80 posttreatment. The ovaries were then removed; one was used for follicular counting, TUNEL, immunohistochemistry and immunofluorescence, while the other was used for Western blot analysis. The proteins studied were BAX, BCL2, t-BID, FAS, FASL, active caspase 8, active caspase 9 and active caspase 3. Follicular apoptosis decreased over time, with the highest values observed at 15 days posttreatment. Granulosa cells were positive for active caspase 3, which showed constant expression levels at all time points. FAS, FASL, t-BID and active caspase 8 showed strong cytoplasmic immunostaining in the oocytes and granulosa cells of the diabetic mice, with significant increases observed at 15, 20 and 70 days posttreatment. BAX expression was slightly higher in the diabetic mouse ovaries than in the control ovaries at 15, 20 and 70 days posttreatment, whereas the highest active caspase 9 expression was at observed 20 days posttreatment. Low BCL2 protein levels were detected in the diabetic mouse ovaries at all time points. This study describes for the first time the behavior of apoptosis-related proteins in the diabetic mouse ovary and shows not only that the FAS/FASL pathway contributes to follicular loss but also that antral follicles are the most affected.

Estrogen receptors in immunity and autoimmunity

Due to the female predominance of autoimmune diseases, the role of gender and sex hormones in the immune system is of long-term interest. Estrogen's primary effects are mediated via estrogen receptors alpha and beta (ER α/β) that are expressed on most immune cells. ERs are nuclear hormone receptors that can either directly bind to estrogen response elements in gene promoters or serve as cofactors with other transcription factors (i.e., NFkB/AP1). Cytoplasmic ER and membrane associated ER impact specific kinase signaling pathways. ERs have prominent effects on immune function in both the innate and adaptive immune responses. Genetic deficiency of ERα in murine models of lupus resulted in significantly decreased disease and prolonged survival, while ERβ deficiency had minimal to no effect in autoimmune models. The protective effect of ERα in lupus is multifactoral. In arthritis models, ERα agonists appears to mediate a protective effect. The modulation of ERα function appears to be a potential target for therapy in autoimmunity.

Genetic polymorphisms in the estrogen receptor beta (ESR2) gene and the risk of epithelial ovarian carcinoma

Ovarian cancer is influenced by exogenous and endogenous estrogens as suggested by experimental and epidemiological evidence. Estrogen receptor beta is a predominant estrogen receptor in the normal ovary. Polymorphisms in the estrogen receptor beta gene (ESR2) might influence epithelial ovarian risk through regulation of cell proliferation and apoptosis. This population-based case-control study included 313 women with epithelial ovarian carcinoma and 574 controls, frequency-matched on age and ethnicity. Unconditional logistic regression was used to test associations of rs1271572, rs1256030, rs1256031, and rs3020450 ESR2 genotypes with ovarian cancer risk. Compared to homozygous common allele carriers, homozygous carriers of variant alleles for rs1271572 [odds ratio (OR) = 1.79, 95% confidence interval (CI):1.15-2.79, p global = 0.01] and rs1256030 [OR = 1.67, CI: 1.08-2.59, p global = 0.04], and women with haplotypes, including variant alleles of rs1271572, rs1256030, and rs1256031 SNPs [OR = 1.75, CI: 1.17-2.63, p global = 0.007], had significantly increased risk of ovarian carcinoma. The association of the rs1271572 genotype was strongest among women who had never used contraceptive steroids (p for interaction = 0.04). Our data suggest that ESR2 might be a susceptibility marker for epithelial ovarian cancer.

Fas ligand expression in TM4 Sertoli cells is enhanced by estradiol "in situ" production

The testis is an immunologically privileged site of the body where Sertoli cells work on to favor local immune tolerance by testicular autoantigens segregation and immunosuppressive factors secretion. Fas/Fas Ligand (FasL) system, expressed prevalently in Sertoli cells, has been considered to be one of the central mechanisms in testis immunological homeostasis. In different cell lines it has been reported that the proapoptotic protein FasL is regulated by 17-beta estradiol (E2). Thus, using as experimental model mouse Sertoli cells TM4, which conserve a large spectrum of functional features present in native Sertoli cells, like aromatase activity, we investigated if estradiol "in situ" production may influence FasL expression. Our results demonstrate that an aromatizable androgen like androst-4-ene-3,17-dione (Delta4) enhanced FasL mRNA, protein content and promoter activity in TM4 cells. The treatment with N(6),2'-O-dibutyryladenosine-3'-5'-cyclic monophosphate [(Bu)(2)cAMP] (simulating FSH action), that is well known to stimulate aromatase activity in Sertoli cells, amplified Delta4 induced FasL expression. Functional studies of mutagenesis, electrophoretic mobility shift (EMSA) and chromatin immunoprecipitation (ChIP) assays revealed that the Sp-1 motif on FasL promoter was required for E2 enhanced FasL expression in TM4 cells. These data let us to recruit FasL among those genes whose expression is up-regulated by E2 through a direct interaction of ERalpha with Sp-1 protein. Finally, evidence that an aromatizable androgen is able to increase FasL expression suggests that E2 production by aromatase activity may contribute to maintain the immunoprivilege status of Sertoli cells.

Genistein attenuates postischemic ovarian injury in a rat adnexal torsion-detorsion model

OBJECTIVE

To investigate the effects of genistein on reperfusion injury in a rat ovarian torsion-detorsion model.

DESIGN

Controlled experimental study.

SETTING

University animal research laboratory.

SUBJECT(S)

Thirty-two Wistar-Albino rats.

INTERVENTION(S)

The rats were divided into four groups. Sham operation was performed in group I. In group II, 5 mg/kg genistein was given intraperitoneally (IP) during laparotomy, and right ovaries were removed 4 hours later. In group III, right ovaries were subjected to 4 hours of adnexal ischemia by use of vascular clips, and after ischemic insult, 4 hours of reperfusion was maintained by removing the clips. In group IV, after the ischemic period, 5 mg/kg genistein was given IP, and 4 hours of reperfusion was maintained. Right ovaries were surgically removed at the end of the procedure in each group.

MAIN OUTCOME MEASURE(S)

Ovarian histopathologic findings were scored and compared among study groups. Serum and ovarian tissue malondialdehyde (MDA), glutathione peroxidase, and superoxide dismutase, levels were measured.

RESULT(S)

Ovarian tissue damage scores were significantly different among groups and were seen to correlate with ovarian tissue MDA levels. Genistein significantly decreased the tissue damage scores, ovarian tissue MDA levels, and serum MDA levels.

CONCLUSION(S)

Genistein attenuates ischemia-reperfusion injury in rat adnexal torsion-detorsion model.

Apoptosis of bovine ovarian surface epithelial cells by Fas antigen/Fas ligand signaling

Ovarian surface epithelial cells (OSEs), a single layer of cells that cover the surface of the ovary, undergo turnover at the site of follicular rupture at ovulation. Greater than 90% of ovarian cancers arise from the OSEs. The objective of this study was to determine whether OSEs have the capacity to regulate their own demise through expression of Fas antigen (Fas) and Fas ligand (FasL) and activation of Fas-mediated apoptosis. In initial experiments, primary cultures of bovine OSEs responded to treatment with recombinant FasL by undergoing apoptosis. The percentage of cell death was not affected by the presence or absence of serum in the media or by co-treatment with interferon-γ, a treatment shown to potentiate Fas-mediated apoptosis in a number of cell types. Subsequent experiments tested the ability of stress-inducing drugs, anisomycin and daunorubicin, to promote apoptosis by stimulating an endogenous Fas–FasL pathway in OSEs. Treatment with FasL, anisomycin or daunorubicin induced cell death and this was suppressed by co-treatment with a peptide inhibitor of caspases, ZVAD. Treatment with anisomycin or daunorubicin in the presence of ZVAD increased expression of FasL mRNA and protein but did not alter expression of Fas mRNA or protein. Treatment of OSEs with a recombinant protein that blocks interaction of FasL with Fas (Fas:Fc) reduced apoptosis in response to anisomycin and daunorubicin, indicating that drug-induced apoptosis was mediated at least partially through endogenous Fas–FasL interactions. In summary, OSEs undergo apoptosis in response to stress-inducing drugs through activation of an endogenous Fas pathway.

Estrogen-induced spermatogenic cell apoptosis occurs via the mitochondrial pathway: role of superoxide and nitric oxide

The detrimental effects of estrogen on testicular function provide a conceptual basis to examine the speculative link between increased exposure to estrogens and spermatogenic cell death. Using an in vitro model, we provide an understanding of the events leading to estrogen-induced apoptosis in cells of spermatogenic lineage. Early events associated with estrogen exposure were up-regulation of FasL and increased generation of H(2)O(2), superoxide, and nitric oxide. The ability of anti-FasL antibodies to prevent several downstream biochemical changes and cell death induced by 17beta-estradiol substantiates the involvement of the cell death receptor pathway. Evidence for the amplification of the death-inducing signals through mitochondria was obtained from the transient mitochondrial hyperpolarization observed after estradiol exposure resulting in cytochrome c release. A combination of nitric oxide and superoxide but not H(2)O(2) was responsible for the mitochondrial hyperpolarization. Mn(III) tetrakis(4-benzoic acid)porphyrin chloride, an intracellular peroxynitrite scavenger, was able to reduce mitochondrial hyperpolarization and cell death. Although nitric oxide augmentation occurred through an increase in the expression of inducible nitric-oxide synthase, superoxide up-regulation was a product of estradiol metabolism. All of the above changes were mediated through an estrogen receptor-based mechanism because tamoxifen, the estrogen receptor modulator, was able to rescue the cells from estrogen-induced alterations. This study establishes the importance of the independent capability of cells of the spermatogenic lineage to respond to estrogens and most importantly suggests that low dose estrogens can potentially cause severe spermatogenic cellular dysfunction leading to impaired fertility even without interference of the hypothalamo-hypophyseal axis.

Involvement of estrogen receptor beta in ovarian carcinogenesis

Knockout and expression studies suggest that estrogen receptor beta (ERbeta) plays a prominent role in ovarian function and pathology. Moreover, ovarian cancers are characterized by high morbidity and low responsiveness to anti-estrogens. Here we demonstrate, using quantitative PCR to measure ERalpha and ERbeta levels in 58 ovarian cancer patients, that ERbeta expression decreased in cysts and ovarian carcinomas as compared with normal ovaries and that this decrease is attributable only to a selective loss in ERbeta expression during cancer progression. To address the question of a possible involvement of ERbeta in ovarian cancers, we restored ERalpha and ERbeta expression in two human ovarian cancer cell lines PEO14 (ERalpha-negative) and BG1 (ERalpha-positive) using adenoviral delivery. ERalpha, but not ERbeta, could induce progesterone receptor and fibulin-1C. Moreover, ERalpha and ERbeta had opposite actions on cyclin D1 gene regulation, because ERbeta down-regulated cyclin D1 gene expression, whereas ERalpha increased cyclin D1 levels. Interestingly, ERbeta expression strongly inhibited PEO14 and BG1 cell proliferation and cell motility in a ligand-independent manner, whereas ERalpha had no marked effect. Induction of apoptosis by ERbeta also contributed to the decreased proliferation of ovarian cancer cells, as shown by Annexin V staining. This study shows that ERbeta is an important regulator of proliferation and motility of ovarian cancer and provides the first evidence for a proapoptotic role of ERbeta. The loss of ERbeta expression may thus be an important event leading to the development of ovarian cancer.

Progesterone-induced apoptosis in immortalized normal and malignant human ovarian surface epithelial cells involves enhanced expression of FasL

Progesterone (P4) has been implicated as a protective factor for epithelial ovarian cancers, yet little is known about its mechanism of action. We previously reported that pregnancy-equivalent doses of P4 inhibited the growth of normal and malignant human ovarian surface epithelial (HOSE) cells. Here, we investigated how P4-induced cell death in two immortalized normal (HOSE 642, HOSE 12-12) and two malignant (OVCA 429, OVCA 432) HOSE cell lines. The exposure of HOSE or OVCA cell cultures to 10(-6) M P4 induced time-dependent increases in early and late apoptotic cells and activation of caspase-8 and -3, but not that of caspase-9. A general caspase inhibitor Z-VAD effectively blocked the P4-induced cell death in a dose-dependent manner. Comparable levels of Fas mRNA and protein were expressed in HOSE and OVCA cell lines, and these levels were unaffected by P4. In contrast, levels of FasL mRNA and protein were higher in OVCA cells than in HOSE cells. Interestingly, the hormone enhanced levels of FasL mRNA and protein in HOSE cells, but lowered their levels in OVCA cells. The exposure of HOSE or OVCA cells to an activating anti-Fas antibody induced cell loss, whereas treatment of cells with a blocking anti-FasL antibody reduced the P4-induced cell loss. Cotreatment of cells with the activating anti-Fas antibody and P4 produced additive effects on cell loss. These results reveal for the first time that P4 induces apoptosis in HOSE and OVCA cells via activation of a caspase-8-initiated Fas/FasL signaling pathway. They also demonstrate differential P4-regulation of FasL expression between HOSE and OVCA cells.

Phenoxodiol--an isoflavone analog--induces apoptosis in chemoresistant ovarian cancer cells

Interference with the innate apoptotic activity is a hallmark of neoplastic transformation and tumor formation. In this study we characterize the cytotoxic effect of phenoxodiol, a synthetic anticancer drug analog of genestein, and demonstrate the mechanism of action by which phenoxodiol affects the components of the Fas apoptotic pathway on ovarian cancer cells. Primary ovarian cancer cells, isolated from ascitic fluids of ovarian cancer patients, resistant to conventional chemotherapy, undergo apoptosis following phenoxodiol treatment. This effect is dependent upon the activation of the caspase system, inhibiting XIAP, an inhibitor of apoptosis, and disrupting FLICE inhibitory protein (FLIP) expression through the Akt signal transduction pathway. We suggest that phenoxodiol is an efficient inducer of cell death in ovarian cancer cells and sensitizes the cancer cells to Fas-mediated apoptosis. We identified FLIP and XIAP signalling pathways as key factors regulating the survival of ovarian cancer cells. These findings demonstrate a novel nontoxic drug that controls FLIP/XIAP function and has the potential to eliminate tumor cells through Fas-mediated apoptosis.

Diethylstilbestrol induces rat spermatogenic cell apoptosis in vivo through increased expression of spermatogenic cell Fas/FasL system

The significant role that estrogens play in spermatogenesis has opened up an exciting area of research in male reproductive biology. The realization that estrogens are essential for proper maintenance of spermatogenesis, as well as growing evidence pointing to the deleterious effects of estrogen-like chemicals on male reproductive health, has made it imperative to dissect the role estrogens play in the male. Using a model estrogen, diethylstilbestrol (DES), to induce spermatogenic cell apoptosis in vivo in the male rat, we provide a new insight into an estrogen-dependent regulation of the Fas-FasL system specifically in spermatogenic cells. We show a distinct increase in Fas-FasL expression in spermatogenic cells upon exposure to diethylstilbestrol. This increase is confined to the spermatid population, which correlates with increased apoptosis seen in the haploid cells. Testosterone supplementation is able to prevent DES-induced Fas-FasL up-regulation and apoptosis in the spermatogenic cells. DES-induced germ cell apoptosis does not occur in Fas-deficient lpr mice. One other important finding is that spermatogenic cells are type II cells, as the increase in Fas-FasL expression in the spermatogenic cells is followed by the cleavage of caspase-8 to its active form, following which Bax translocates to the mitochondria and precipitates the release of cytochrome c that is accompanied by a drop in mitochondrial potential. Subsequent to this, activation of caspase-9 occurs that in turn activates caspase-3 leading to the cleavage of poly(ADP-ribose) polymerase. Taken together, the data indicate that estrogen-like chemicals can precipitate apoptotic death in spermatogenic cells by increasing the expression of spermatogenic cell Fas-FasL, thus initiating apoptosis in the same lineage of cells through the activation of the apoptotic pathway chosen by type II cells.

Interaction of the estrogen receptors with the Fas ligand promoter in human monocytes

The predominance of autoimmune diseases among women suggests that estrogen may modulate immune function. Monocytes and macrophages are important in initiating, maintaining, and resolving inflammatory responses through cell-signaling molecules, which control immune cell survival. One important mechanism of cell survival is mediated by the Fas/Fas ligand (FasL) system. In this study, the link between estrogen, monocytes/macrophages, and the Fas/FasL system was investigated. Estrogen treatment increased FasL expression in monocytes through the binding of the estrogen receptors (ER) to the estrogen recognizing elements and AP-1 motifs present at the FasL promoter. Furthermore, estrogen induced apoptosis in monocytes expressing ERbeta, but not in monocyte-differentiated macrophages expressing ERalpha. The expression of either ERalpha or ERbeta and their response to estrogen in monocytes was found to be dependent on the their stage of cell differentiation. Previously, we have shown that estrogen replacement therapy in postmenopausal women decreased the number of circulating monocytes. In this study, we have characterized the molecular mechanism by which estrogen regulates monocytes homeostasis. These findings indicate that estrogen may regulate immune cell survival through the Fas/FasL system. There is biological relevance to these findings in view of studies showing that accumulation of activated monocytes is involved in the pathogenesis of conditions such as vasculititis, arteriosclerosis, and rheumatoid arthritis.

Role of the Fas/Fas ligand system in female reproductive organs: survival and apoptosis

For centuries, the question of "whether there is life after death" has intrigued the mind of philosophers and the same question fascinates researchers in the field of apoptosis today. The death of a cell is by no means the end of the story. On the contrary, growing evidence suggests that the clearance of apoptotic bodies by macrophages is an important regulatory component in tissue renewal. Without death by apoptosis, the life of reproductive tissues and their function would not be possible. The survival signals that counteract cell death also prepare the cells for apoptosis, and dead cells are important stimuli for tissue survival. The Fas/Fas ligand system is an important mediator of apoptosis and is an excellent example of this apparently contradictory phenomenon.