The Pathogenetic Study Of Endometrial And Ovarian Carcinomas

Endometrial carcinoma is diagnosed in approximately 39,080 women yearly in the United States and causes approximately 7,400 deaths, with a worldwide incidence and mortality of 142,000 and 42,000, respectively. A dualistic model of endometrial carcinogenesis has been proposed since 1980s based on light microscopic appearance, clinical behavior, and epidemiology, which includes type I and type II cancers. In the last decade, progress has been greatest in molecular and histologic resolution of precursor of type I cancer, resulting in a cohesive model of endometrial carcinogenesis encompassing both genetic and hormonal factors, revised precancer diagnostic criteria, and novel prevention strategies. In contrast to type I precancer, studies on the type II cancer, which is typical of endometrial serous carcinoma (ESC), are very much limited.Ovarian cancer remains the fourth most common cancer death in women in the United States and is the most lethal among gynecologic malignancies. The vast majority (80-90%) originate from ovarian surface epithelium (OSE). As is clear that OSE consists of only a single layer of flat-to-cuboidal epithelial cells with few distinguished features, but little is known about the mechanisms of its malignant transformation. Therfefore, there is a certain need to understand its pathogenesis with a hope to find an effective way to control the cancer development.Accordingly, this study was designed with the purpose to further define the pathogenesis involved in ESC and ovarian epithelial carcinoma (OEC), which is divided into the following two parts:1. P53 analysis favoring endometrial glandular dysplasia as a precancer for endometrial serous carcinoma2. The balancing process between gonadotropins in ovarian carcinogenesis via prohibitin PART ONE: P53 ANALYSIS FAVOURING ENDOMETRIAL GLANDULAR DYSPLASIA AS A PRECANCER FOR ENDOMETRIAL SEROUS CARCINOMABackground and Purpose: Endometrial serous carcinoma (ESC) is an uncommon but aggressive subtype of endometrial carcinoma that is associated with dismal prognosis. Endometrial glandular dysplasia (EmGD) has been recently proposed to be a putative precursor to ESC. The purpose of this study is to determine if EmGD is genetically linked to ESC and it can be used for early detection.Materials and Methods: The tumor suppressor p53 gene was sequenced from serial samples of benign and neoplastic endometria with serous differentiation. The study group contained 15 neoplastic uteri including 9 pure ESC, 2 mixed serous and clear cell carcinoma, 3 serous endometrial intraepithelial carcinoma (E1C) and 1 EmGD alone. The control group had 12 age-matched benign uteri. A total of 115 informative samples were obtained including 31 resting endometrium (RE), 37 EmGD, 25 serous EIC, and 22 ESC. An additional 24 RE samples were retrieved from the 12 benign uteri. At least one representative section from each uterus was used for p53 immunohistochemical staining to correlate p53 overexpression with gene mutation status.Results: The mutations of p53 were detected in 0, 43.2%, 72.0%, and 95.5% in RE, EmGD, serous EIC and ESC, respectively. Among the 15 neoplastic uteri, 11 uteri contained multiple EmGDs, ESC and/or serous EIC. In six (55%) at least one identical p53 gene mutant was shared by EmGD, serous EIC and/or ESC. Majority lesions showed overexpression of p53 protein, which was significantly correlated with p53 gene mutation (P < 0.01). Conclusions: This genetic evidence strongly supports that EmGD represents the precancer of ESC or serous EIC. Mutation of p53 gene is probably one of the most important factors to initiate the endometrial serous carcinogenesis. Correct identification of EmGD will provide us an opportunity of early diagnosis and a potential effective therapeutic modality to control ESC.PART TWO: THE BALANCING PROCESS BETWEEN GONADOTROPINS IN OVARIAN CARCINOGENESIS VIA PROHIBITINBackground and Purpose: Ovarian carcinoma remains the leading cause of death from gynecological malignancies. Despite its clinical significance, the factors that regulate the development and progression of ovarian carcinoma are the least understood among all major human malignancies. The roles of gonadotropins in ovarian epithelial cancer (OEC) have received increasing attention. We have previously found that the stimulatory effect of ovarian epithelial tumor (OET) growth induced by follicle-stimulating hormone (FSH) could be blocked by luteinizing hormone (LH). The aim of this study is designed to elucidate the potential molecular mechanism(s) underlying this phenomenon.Materials and Methods: OET cells (MCV152) were treated with LH and FSH or vehicle and total proteins were analyzed by two-dimensional gel electrophoresis (2DGE). Then liquid chromatography tandem mass spectrometry (LC-MS/MS) was used to identify significantly altered proteins. Further Western blot and immunohistochemistry were used to validate the target protein (prohibitin). After silencing prohibitin by RNA interference, the cellular growth/inhibitory effects of prohibitin were examined by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) and fluorescence-activated cell sorting (FACS) analysis.Results: Prohibitin expression in OET cells was specifically up-regulated by LH, not by FSH. An extra 1.5-fold prohibitin was induced when LH was used simultaneously with FSH. LH induced prohibitin increment was in a dose-dependent manner with a maximum response at 24 hrs of stimulation with the optimal LH concentration of 50 mIU/mL. 40% increased cell numbers were observed after prohibitin silencing and subsequent FACS showed an apparent shift of cells from G0/G1 to S and G2/M phases. In ovarian tissue, prohibitin expression was basically unanimous in benign ovarian tissues with the highest expression in luteinized ovarian stromal cells, follicular cells, ovarian surface epithelium, and ovarian epithelial inclusions with serous differentiation. The level of prohibitin expression is progressively lost in the process of OET development and reversely associated with OEC grade.Conclusions: These results show that LH and FSH play an opposing role in OET cell growth. Up-regulation of prohibitin expression by LH is likely part of the mechanism of LH blocking the stimulating effect of FSH on OET cells. Gradual loss of prohibitin expression from OSE and OEI to OEC may be indicative of an imbalance of FSH and LH contributing to the OEC development and progression. Universal expression of prohibitin in the putative precursors of OEC may be critical to maintain their inactive growth status in normal situation. It is important to further investigate the combined effects of gonadotropins in OEC development, the knowledge of which may ultimately be used for OEC prevention. In summing up, the study shed light on the pathogenesis involved in ESC and OEC, with a new precancer entity demonstrated and a new hypothesis proposed individually. Both of them are carried out on the prelimitary investigations as evidence by several published papers. The current in-deep study is characterized by the following key points:1. EmGD, which was first established by our group, shows much better evidence as a precursor lesion of ESC, instead of the previous serous EIC. This study provides genetic evidence to support its role as a precancer to ESC.2. Another novel finding is prohibitin, whose normal expression could protect against OEC, while the decreased and loss of expression increased the risk of ovarian carcinogenesis.3. "Gonadotropin balancing theory", stating that during the ovarian carcinogenesis, there is a balancing process between LH and FSH, is also a new accomplishment. Up-regulation of prohibitin expression by LH is likely part of the mechanisms of LH blocking the stimulating effect by FSH on OET cells.