Ovarian Cancer Pathogenesis: A Model in Evolution

Ovarian cancer is a deadly disease for which there is no effective means of early detection. Ovarian carcinomas comprise a diverse group of neoplasms, exhibiting a wide range of morphological characteristics, clinical manifestations, genetic alterations, and tumor behaviors. This high degree of heterogeneity presents a major clinical challenge in both diagnosing and treating ovarian cancer. Furthermore, the early events leading to ovarian carcinoma development are poorly understood, thus complicating efforts to develop screening modalities for this disease. Here, we provide an overview of the current models of ovarian cancer pathogenesis, highlighting recent findings implicating the fallopian tube fimbria as a possible site of origin of ovarian carcinomas. The ovarian cancer model will continue to evolve as we learn more about the genetics and etiology of this disease

The new face of ovarian cancer modeling: better prospects for detection and treatment

Ovarian cancer has a disproportionately high mortality rate because patients typically present with late-stage metastatic disease. The vast majority of these deaths are from high-grade serous carcinoma. Recent studies indicate that many of these tumors arise from the fallopian tube and subsequently metastasize to the ovary. This may explain why such tumors have not been detected at early stage as detection efforts have been focused purely on the ovary. In keeping with this leap in understanding other advances such as the development of ex-vivo models and immortalization of human fallopian tube epithelial cells, and the use of integrated genomic analyses to identify hundreds of novel candidate oncogenes and tumor suppressors potentially involved in tumorigenesis now engender hope that we can begin to truly define the differences in pathogenesis between fallopian tube and ovarian-derived tumors. In doing so, we can hopefully improve early detection, treatment, and outcome

Role of miR-182 in response to oxidative stress in the cell fate of human fallopian tube epithelial cells

High grade serous ovarian carcinoma (HGSC) is a DNA instable tumor and its precursor is commonly found originating from the fimbriated end of the fallopian tube secretory epithelial (FTSE) cells. The local stresses via ovulation and related inflammation are risks for HGSC. In this study, we examined the cellular and molecular responses of FTSE cells to stress. We found that excess intracellular reactive oxygen species (ROS) in normal FTSE cells upregulated a subset of microRNA expression (defined as ROSmiRs). Most ROSmiRs' expression and function were influenced and regulated by p53, and together they drove the cells into stress-induced premature senescence (SIPS). However, ROS-induced miR-182 is regulated by β-catenin, not by p53. In normal FTSE cells, miR-182 overexpression triggers cellular senescence by p53-mediated upregulation of p21. Conversely, in cells with p53 mutations, miR-182 overexpression no longer enhances p21 but functions as an “Onco-miR”. p53 dysfunction is a prerequisite for miR-182-mediated tumorigenesis. In addition, we found that human follicular fluid could significantly induce intracellular ROS in normal FTSE cells. These findings suggest that ROS and p53 mutations may trigger a series of events, beginning with overexpressing miR-182 by ROS and β-catenin, impairing the DNA damage response, promoting DNA instability, bypassing senescence and eventually leading to DNA instable tumors in FTSE cells

Cis-eQTL analysis and functional validation of candidate susceptibility genes for high-grade serous ovarian cancer

Genome-wide association studies have reported 11 regions conferring risk of high-grade serous epithelial ovarian cancer (HGSOC). Expression quantitative trait locus (eQTL) analyses can identify candidate susceptibility genes at risk loci. Here we evaluate cis-eQTL associations at 47 regions associated with HGSOC risk (PPeer reviewe

Cis-eQTL analysis and functional validation of candidate susceptibility genes for high-grade serous ovarian cancer

Genome-wide association studies have reported 11 regions conferring risk of high-grade serous epithelial ovarian cancer (HGSOC). Expression quantitative trait locus (eQTL) analyses can identify candidate susceptibility genes at risk loci. Here we evaluate cis-eQTL associations at 47 regions associated with HGSOC risk (P≤10−5). For three cis-eQTL associations (P<1.4 × 10−3, FDR<0.05) at 1p36 (CDC42), 1p34 (CDCA8) and 2q31 (HOXD9), we evaluate the functional role of each candidate by perturbing expression of each gene in HGSOC precursor cells. Overexpression of HOXD9 increases anchorage-independent growth, shortens population-doubling time and reduces contact inhibition. Chromosome conformation capture identifies an interaction between rs2857532 and the HOXD9 promoter, suggesting this SNP is a leading causal variant. Transcriptomic profiling after HOXD9 overexpression reveals enrichment of HGSOC risk variants within HOXD9 target genes (P=6 × 10−10 for risk variants (P<10−4) within 10 kb of a HOXD9 target gene in ovarian cells), suggesting a broader role for this network in genetic susceptibility to HGSOC

Stathmin 1 and p16(INK4A) are sensitive adjunct biomarkers for serous tubal intraepithelial carcinoma.

ObjectiveTo credential Stathmin 1 (STMN1) and p16(INK4A) (p16) as adjunct markers for the diagnosis of serous tubal intraepithelial carcinoma (STIC), and to compare STMN1 and p16 expression in p53-positive and p53-negative STIC and invasive high-grade serous carcinoma (HGSC).MethodsImmunohistochemistry (IHC) was used to examine STMN1 and p16 expression in fallopian tube specimens (n=31) containing p53-positive and p53-negative STICs, invasive HGSCs, and morphologically normal FTE (fallopian tube epithelium). STMN1 and p16 expression was scored semiquantitatively by four individuals. The semiquantitative scores were dichotomized, and reported as positive or negative. Pooled siRNA was used to knockdown p53 in a panel of cell lines derived from immortalized FTE and HGSC.ResultsSTMN1 and p16 were expressed in the majority of p53-positive and p53-negative STICs and concomitant invasive HGSCs, but only scattered positive cells were present in morphologically normal FTE. Both proteins were expressed consistently across multiple STICs from the same patient and in concomitant invasive HGSC. Knockdown of p53 in immortalized FTE cells and in four HGSC-derived cell lines expressing different missense p53 mutations did not affect STMN1 protein levels.ConclusionsThis study demonstrates that STMN1 and p16 are sensitive and specific adjunct biomarkers that, when used with p53 and Ki-67, improve the diagnostic accuracy of STIC. The addition of STMN1 and p16 helps to compensate for practical limitations of p53 and Ki-67 that complicate the diagnosis in up to one third of STICs

YAP Induces High-Grade Serous Carcinoma in Fallopian Tube Secretory Epithelial Cells

Accumulating evidence indicates that ovarian high-grade serous carcinoma (HGSC) originates from Fallopian tube secretory epithelial cells (FTSECs). However, the molecular mechanisms underlying the initiation and progression of HGSC derived from FTSECs remains unclear. In the present study, we found that the Hippo/YAP signaling pathway plays a critical role in the initiation and progression of Fallopian tube and ovarian HGSC. Importantly, YAP was overexpressed in inflammatory and cancerous Fallopian tube tissues. Further, overexpression of wild-type YAP, or constitutively active YAP in immortalized FTSECs, induced cell proliferation, migration, colony formation, and tumorigenesis. Moreover, the Hippo/YAP and the fibroblast growth factor (FGF) signaling pathways formed an autocrine/paracrine positive feedback loop to drive the progression of the FTSECs-derived HGSC. Evidence in this study strongly suggests that combined therapy with inhibitors of YAP (such as verteporfin) and FGFRs (such as BGJ398) can provide a novel therapeutic strategy to treat Fallopian tube and ovarian HGSC

Mesenchymal gene program-expressing ovarian cancer spheroids exhibit enhanced mesothelial clearance.

Metastatic dissemination of ovarian tumors involves the invasion of tumor cell clusters into the mesothelial cell lining of peritoneal cavity organs; however, the tumor-specific factors that allow ovarian cancer cells to spread are unclear. We used an in vitro assay that models the initial step of ovarian cancer metastasis, clearance of the mesothelial cell layer, to examine the clearance ability of a large panel of both established and primary ovarian tumor cells. Comparison of the gene and protein expression profiles of clearance-competent and clearance-incompetent cells revealed that mesenchymal genes are enriched in tumor populations that display strong clearance activity, while epithelial genes are enriched in those with weak or undetectable activity. Overexpression of transcription factors SNAI1, TWIST1, and ZEB1, which regulate the epithelial-to-mesenchymal transition (EMT), promoted mesothelial clearance in cell lines with weak activity, while knockdown of the EMT-regulatory transcription factors TWIST1 and ZEB1 attenuated mesothelial clearance in ovarian cancer cell lines with strong activity. These findings provide important insights into the mechanisms associated with metastatic progression of ovarian cancer and suggest that inhibiting pathways that drive mesenchymal programs may suppress tumor cell invasion of peritoneal tissues