Apoptosis: a link between cancer genetics and chemotherapy.

Mammalian ovaries consist of follicles as basic functional units. The total number of ovarian follicles is determined early in life, and the depletion of this pool leads to reproductive senescence. Each follicle develops to either ovulate or, more likely, to undergo degeneration. The dynamics of ovarian follicle development have interested endocrinologists and developmental biologists for many years. With the advent of assisted reproductive techniques in humans, the possibility of regulating follicle development in vivo and in vitro has gained clinical relevance. In this review, we focus upon key branching points during the development of ovarian follicles as well as factors involved in determining the eventual destiny of individual follicles. We discuss inconsistencies in the literature regarding the definitions of follicle recruitment and selection and propose to name the two major steps of follicle development as initial and cyclic recruitment, respectively. Because some of these disparities have arisen due to differences in the animal systems studied, we also compare the development of the ovarian follicles of both humans and rats. We also review the status of knowledge of several puzzling clinical issues that may provide important clues toward unlocking the mechanisms of follicle development.

https://redlara.com/images/arq/LOC1_recrutamento.pdf

Initial and cyclic recruitment of ovarian follicles.

Malignant cells are known to have accelerated metabolism, high glucose requirements, and increased glucose uptake. Transport of glucose across the plasma membrane of mammalian cells is the first rate-limiting step for glucose metabolism and is mediated by facilitative glucose transporter (GLUT) proteins. Increased glucose transport in malignant cells has been associated with increased and deregulated expression of glucose transporter proteins, with overexpression of GLUT1 and/or GLUT3 a characteristic feature. Oncogenic transformation of cultured mammalian cells causes a rapid increase of glucose transport and GLUT1 expression via interaction with GLUT1 promoter enhancer elements. In human studies, high levels of GLUT1 expression in tumors have been associated with poor survival. Studies indicate that glucose transport in breast cancer is not fully explained by GLUT1 or GLUT3 expression, suggesting involvement of another glucose transporter. Recently, a novel glucose transporter protein, GLUT12, has been found in breast and prostate cancers. In human breast and prostate tumors and cultured cells, GLUT12 is located intracellularly and at the cell surface. Trafficking of GLUT12 to the plasma membrane could therefore contribute to glucose uptake. Several factors have been implicated in the regulation of glucose transporter expression in breast cancer. Hypoxia can increase GLUT1 levels and glucose uptake. Estradiol and epidermal growth factor, both of which can play a role in breast cancer cell growth, increase glucose consumption. Estradiol and epidermal growth factor also increase GLUT12 protein levels in cultured breast cancer cells. Targeting GLUT12 could provide novel methods for detection and treatment of breast and prostate cancer.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/jcp.20166

Molecular and cellular regulation of glucose transporter (GLUT) proteins in cancer

Apoptosis is a form of programmed cell death that results in the orderly and efficient removal of damaged cells, such as those resulting from DNA damage or during development Apoptosis can be triggered by signals from within the cell, such as genotoxic stress, or by extrinsic signals, such as the binding of ligands to cell surface death receptors Deregulation in apoptotic cell death machinery is an hallmark of cancer Apoptosis alteration is responsible not only for tumor development and progression but also for tumor resistance to therapies Most anticancer drugs currently used in clinical oncology exploit the intact apoptotic signaling pathways to trigger cancer cell death Thus, defects in the death pathways may result in drug resistance so limiting the efficacy of therapies Therefore, a better understanding of the apoptotic cell death signaling pathways may improve the efficacy of cancer therapy and bypass resistance This review will highlight the role of the fundamental regulators of apoptosis and how their deregulation, including activation of anti-apoptotic factors (ie, Bcl-2, Bcl-xL, etc) or inactivation of pro-apoptotic factors (ie, p53 pathway) ends up in cancer cell resistance to therapies In addition, therapeutic strategies aimed at modulating apoptotic activity are briefly discussed

Apoptosis as anticancer mechanism: function and dysfunction of its modulators and targeted therapeutic strategies

Menopause is the final step in the process referred to as ovarian ageing. The age related decrease in follicle numbers dictates the onset of cycle irregularity and the final cessation of menses. The parallel decay in oocyte quality contributes to the gradual decline in fertility and the final occurrence of natural sterility. Endocrine changes mainly relate to the decline in the negative feedback from ovarian factors at the hypothalamo-pituitary unit. The declining cohort of antral follicles with age first results in graduallyelevatedFSHlevels,followedbysubsequentstagesofovertcycleirregularity.Thegradualdecline in the size of the antral follicle cohort is best represented by decreasing levels of anti-Mullerian hormone. The variability of ovarian ageing among women is evident from the large variation in age at menopause. The identificationofwomenwhohaveseverelydecreasedovarianreservefortheirageisclinicallyrelevant.Ovarian reserve tests have appeared to be fairly accurate in predicting response to ovarian stimulation in the assisted reproductive technology (ART) setting. The capacity to predict the chances for spontaneous pregnancy or pregnancy after ART appears very limited. As menopause and the preceding decline in oocyte quality seem to have a fixed time interval, tests that predict the age at menopause may be useful to assess individual reproductive lifespan. Especially genetic studies, both addressing candidate gene and genome wide association, have identified several interesting loci of small genetic variation that may determine fetal follicle pool development and subsequent wastage of his pool over time. Improved knowledge of the ovarian ageing mechanisms may ultimately provide tools for prediction of menopause and manipulation of the early steps of folliculogenesis for the purpose of contraception and fertility lifespan extension. (Endocrine Reviews 30: 465–493, 2009)

Ovarian Aging: Mechanisms and Clinical Consequences

Cisplatin-centeredchemotherapy is a key treatment for ovarian cancer, but resistance to chemotherapeutic agents remains a major cause of treatment failure. Multiple factors are known to contribute to the development of this chemoresistance. Although it has been demonstrated that X-linked inhibitor of apoptosis protein (Xiap) prevents apoptosis by inhibiting effector caspases, if and how it is important in chemoresistance in ovarian cancer has not been studied. The effects of Xiap down-regulation and/or restoration of wild type p53 by recombinant adenovirus infection were examined on four ovarian epithelial cancer cell lines [C13*, A2780-s (wild type p53), A2780-cp (mutant p53), and SKOV3 (null p53)]. Apoptosis and protein expression ( e.g., Xiap, caspase-3, p53, MDM2, and p21waf1) were assessed by Hoechst 33258 stain and Western blot, respectively. We demonstrated that Xiap down-regulation following adenoviral antisense expression induces apoptosis in the wild-type p53 cells, but not in the mutated or null cells. Xiap down-regulation resulted in caspase-3 activation, caspase-mediated MDM2 processing, and p53 accumulation. Restoration of wild type p53 in the p53-mutated or -null cells significantly enhanced the proapoptotic effect of Xiap antisense expression. Down-regulation of Xiap induced apoptosis in chemoresistant ovarian cancer cells, a process dependent on p53 status.

https://cancerres.aacrjournals.org/content/canres/60/20/5659.full.pdf

Down-Regulation of X-linked Inhibitor of Apoptosis Protein Induces Apoptosis in Chemoresistant Human Ovarian Cancer Cells

The preantral-early antral follicle transition is the penultimate stage of follicular development in terms of gonadotropin dependence and follicle destiny (growth versus atresia). Follicular growth during this period is tightly regulated by oocyte-granulosa-theca cell interactions. Formation of the theca cell layer is a key event that occurs during this transitional stage. Granulosal factor(s) stimulates the recruitment of theca cells from cortical stromal cells, while oocyte-derived growth differentiation factor-9 (GDF-9) is involved in the differentiation of theca cells during this early stage of follicular development. The preantral to early antral transition is most susceptible to follicular atresia. GDF-9 promotes follicular survival and growth during transition from preantral stage to early antral stage by suppressing granulosa cell apoptosis and follicular atresia. GDF-9 also enhances preantral follicle growth by up-regulating theca cell androgen production. Thecal factor(s) promotes granulosa cell proliferation and suppress granulosa cell apoptosis. Understanding the intraovarian mechanisms in the regulation of follicular growth and atresia during this stage may be of clinical significance in the selection of the best quality germ cells for assisted reproduction. In addition, since certain ovarian dysfunctions, such as polycystic ovarian syndrome and gonadotropin poor-responsiveness, are consequences of dysregulated follicle growth at this transitional stage, understanding the molecular and cellular mechanisms in the control of follicular development during the preantral-early antral transition may provide important insight into the pathophysiology and rational treatment of these conditions.

/pdf/oocyte-granulosa-theca-cell-interactions-during-preantral-4kcv23uo36.pdf

Oocyte-granulosa-theca cell interactions during preantral follicular development

Ovarian follicular atresia represents a selection process that ensures the release of only healthy and viable oocytes during ovulation. The transition from preantral to early antral stage is the penultimate stage of development in terms of gonadotropin dependence and follicle destiny (survival/growth vs. atresia). We have examined whether and how oocyte-derived growth differentiation factor 9 (GDF-9) and FSH regulate follicular development and atresia during the preantral to early antral transition, by a novel combination of in vitro gene manipulation (i.e. intraoocyte injection of GDF-9 antisense oligos) and preantral follicle culture. Injection of GDF-9 antisense suppressed basal and FSH-induced preantral follicle growth in vitro, whereas addition of GDF-9 enhanced basal and FSH-induced follicular development. GDF-9 antisense activated caspase-3 and induced apoptosis in cultured preantral follicles, a response attenuated by exogenous GDF-9. GDF-9 increased phospho-Akt content in granulosa cells of early antral follicles. Although granulosa cell apoptosis induced by ceramide was attenuated by the presence of GDF-9, this protective effect of GDF-9 was prevented by the phosphatidylinositol 3-kinase inhibitor LY294002 and a dominant negative form of Akt. Injection of GDF-9 antisense decreased FSH receptor mRNA levels in cultured follicles, a response preventable by the presence of exogenous GDF-9. The data suggest that GDF-9 is antiapoptotic in preantral follicles and protects granulosa cells from undergoing apoptosis via activation of the phosphatidylinositol 3-kinase/Akt pathway. An adequate level of GDF-9 is required for follicular FSH receptor mRNA expression. GDF-9 promotes follicular survival and growth during the preantral to early antral transition by suppressing granulosa cell apoptosis and follicular atresia.

/pdf/growth-differentiation-factor-9-is-antiapoptotic-during-zbfpxf55mj.pdf

Growth Differentiation Factor 9 Is Antiapoptotic during Follicular Development from Preantral to Early Antral Stage

Regulation of mammalian follicular development is tightly regulated by both cell death and survival signals, including endocrine (e.g. gonadotropin) and intra-ovarian regulators (e.g. Nodal and GDF9). The destiny of the individual follicle (growth/ovulation or atresia) is dependent on a delicate balance in the expression and action of factors promoting follicular cell proliferation, growth and differentiation, and of those promoting programmed cell death (apoptosis). Development of the follicle from the primordial to preantral stage is regulated by oocyte-derived factors including GDF9 and BMP15, and is not dependent on gonadotropin support (gonadotropin-independent stage). As the follicle transits into the early antral stage it becomes responsive to gonadotropin (gonadotropin-responsive stages) and further development renders the follicle completely dependent on the presence of gonadotropin while modulated by intra-ovarian regulators (gonadotropin-dependent). Follicle fate is also regulated by pro-apoptotic factors such as the intraovarian regulator Nodal, which is secreted by the theca and promotes apoptosis of differentiated granulosa cells through a mechanism involving Smad2 signaling and suppression of the PI3K/Akt pathway. The intracellular protein prohibitin (PHB) appears to have a dual role during folliculogenesis; acting as a cell survival factor in undifferentiated cells, and as a pro-apoptotic factor following differentiation. Further investigations of the interplay between these endocrine and ovarian regulators will lead to a better understanding into the regulation of follicular development and atresia, allowing development of new techniques for assisted reproduction.

Gonadotropin and intra-ovarian signals regulating follicle development and atresia: the delicate balance between life and death.

We evaluated whether tracer FDG uptake, quantified as an SUV by PET in ovarian epithelial tumors, correlates with clinical stage, tumor grade, cell proliferation and glucose metabolism, all of which are biomarkers for response to chemotherapy, prognosis and overall survival in ovarian cancer patients. Seventeen patients suspected of having ovarian cancer by physical examination, tumor marker analysis and anatomic imaging (such as sonography, CT and/or MRI) underwent whole-body FDG-PET within the 2 weeks prior to surgery. Seventeen epithelial ovarian tumor specimens (13 malignant tumors, 5 at stage I, 2 at stage II, 6 at stage III; 2 borderline tumors; and 2 benign lesions) were available for pathologic evaluation. They were graded histopathologically, and immunohistochemistry for MIB-1 (proliferation index marker) and GLUT-1 was performed. Correlation between FDG uptake and clinical stage, GLUT-1 expression, MIB-1 LI and histologic grading score was determined. No positive correlation was observed between FDG uptake and clinical stage (p=0.14). Intensity of GLUT-1 expression (r=0.76, p=0.001), MIB-1 LI (r=0.457, p=0.014) and histologic grading score (r=0.692, p=0.005) showed statistically significant positive correlations with FDG uptake. Stepwise logistic regression analysis revealed that expression of GLUT-1 transporters was the strongest parameter (r=0.760, p=0.0004) by which to predict positive FDG uptake. Therefore, glucose consumption, as determined by analysis of SUVs in FDG-PET, may be a noninvasive biomarker for ovarian epithelial tumors.

Expression of GLUT‐1 glucose transfer, cellular proliferation activity and grade of tumor correlate with [F‐18]‐fluorodeoxyglucose uptake by positron emission tomography in epithelial tumors of the ovary

Fumikazu Kotsuji

Papers

Down-Regulation of X-linked Inhibitor of Apoptosis Protein Induces Apoptosis in Chemoresistant Human Ovarian Cancer Cells

Oocyte-granulosa-theca cell interactions during preantral follicular development

Growth Differentiation Factor 9 Is Antiapoptotic during Follicular Development from Preantral to Early Antral Stage

Gonadotropin and intra-ovarian signals regulating follicle development and atresia: the delicate balance between life and death.

Expression of GLUT‐1 glucose transfer, cellular proliferation activity and grade of tumor correlate with [F‐18]‐fluorodeoxyglucose uptake by positron emission tomography in epithelial tumors of the ovary