Establishment of Patient-Derived Tumor Xenograft Models of Epithelial Ovarian Cancer for Preclinical Evaluation of Novel Therapeutics.

Purpose: Ovarian cancer is the leading cause of death from gynecologic malignancy in the United States, with high rates of recurrence and eventual resistance to cytotoxic chemotherapy. Model systems that allow for accurate and reproducible target discovery and validation are needed to support further drug development in this disease.Experimental Design: Clinically annotated patient-derived xenograft (PDX) models were generated from tumor cells isolated from the ascites or pleural fluid of patients undergoing clinical procedures. Models were characterized by IHC and by molecular analyses. Each PDX was luciferized to allow for reproducible in vivo assessment of intraperitoneal tumor burden by bioluminescence imaging (BLI). Plasma assays for CA125 and human LINE-1 were developed as secondary tests of in vivo disease burden.Results: Fourteen clinically annotated and molecularly characterized luciferized ovarian PDX models were generated. Luciferized PDX models retain fidelity to both the nonluciferized PDX and the original patient tumor, as demonstrated by IHC, array CGH, and targeted and whole-exome sequencing analyses. Models demonstrated diversity in specific genetic alterations and activation of PI3K signaling pathway members. Response of luciferized PDX models to standard-of-care therapy could be reproducibly monitored by BLI or plasma markers.Conclusions: We describe the establishment of a collection of 14 clinically annotated and molecularly characterized luciferized ovarian PDX models in which orthotopic tumor burden in the intraperitoneal space can be followed by standard and reproducible methods. This collection is well suited as a platform for proof-of-concept efficacy and biomarker studies and for validation of novel therapeutic strategies in ovarian cancer. Clin Cancer Res; 23(5); 1263-73. ©2016 AACR.

Drug-induced death signaling strategy rapidly predicts cancer response to chemotherapy.

There is a lack of effective predictive biomarkers to precisely assign optimal therapy to cancer patients. While most efforts are directed at inferring drug response phenotype based on genotype, there is very focused and useful phenotypic information to be gained from directly perturbing the patient's living cancer cell with the drug(s) in question. To satisfy this unmet need, we developed the Dynamic BH3 Profiling technique to measure early changes in net pro-apoptotic signaling at the mitochondrion ("priming") induced by chemotherapeutic agents in cancer cells, not requiring prolonged ex vivo culture. We find in cell line and clinical experiments that early drug-induced death signaling measured by Dynamic BH3 Profiling predicts chemotherapy response across many cancer types and many agents, including combinations of chemotherapies. We propose that Dynamic BH3 Profiling can be used as a broadly applicable predictive biomarker to predict cytotoxic response of cancers to chemotherapeutics in vivo.

An in-tumor genetic screen reveals that the BET bromodomain protein, BRD4, is a potential therapeutic target in ovarian carcinoma.

High-grade serous ovarian carcinoma (HGSOC) is the most common and aggressive form of epithelial ovarian cancer, for which few targeted therapies exist. To search for new therapeutic target proteins, we performed an in vivo shRNA screen using an established human HGSOC cell line growing either subcutaneously or intraperitoneally in immunocompromised mice. We identified genes previously implicated in ovarian cancer such as AURKA1, ERBB3, CDK2, and mTOR, as well as several novel candidates including BRD4, VRK1, and GALK2. We confirmed, using both genetic and pharmacologic approaches, that the activity of BRD4, an epigenetic transcription modulator, is necessary for proliferation/survival of both an established human ovarian cancer cell line (OVCAR8) and a subset of primary serous ovarian cancer cell strains (DFs). Among the DFs tested, the strains sensitive to BRD4 inhibition revealed elevated expression of either MYCN or c-MYC, with MYCN expression correlating closely with JQ1 sensitivity. Accordingly, primary human xenografts derived from high-MYCN or c-MYC strains exhibited sensitivity to BRD4 inhibition. These data suggest that BRD4 inhibition represents a new therapeutic approach for MYC-overexpressing HGSOCs.

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.

Profiles of genomic instability in high-grade serous ovarian cancer predict treatment outcome.

PURPOSE: High-grade serous cancer (HGSC) is the most common cancer of the ovary and is characterized by chromosomal instability. Defects in homologous recombination repair (HRR) are associated with genomic instability in HGSC, and are exploited by therapy targeting DNA repair. Defective HRR causes uniparental deletions and loss of heterozygosity (LOH). Our purpose is to profile LOH in HGSC and correlate our findings to clinical outcome, and compare HGSC and high-grade breast cancers. EXPERIMENTAL DESIGN: We examined LOH and copy number changes using single nucleotide polymorphism array data from three HGSC cohorts and compared results to a cohort of high-grade breast cancers. The LOH profiles in HGSC were matched to chemotherapy resistance and progression-free survival (PFS). RESULTS: LOH-based clustering divided HGSC into two clusters. The major group displayed extensive LOH and was further divided into two subgroups. The second group contained remarkably less LOH. BRCA1 promoter methylation was associated with the major group. LOH clusters were reproducible when validated in two independent HGSC datasets. LOH burden in the major cluster of HGSC was similar to triple-negative, and distinct from other high-grade breast cancers. Our analysis revealed an LOH cluster with lower treatment resistance and a significant correlation between LOH burden and PFS. CONCLUSIONS: Separating HGSC by LOH-based clustering produces remarkably stable subgroups in three different cohorts. Patients in the various LOH clusters differed with respect to chemotherapy resistance, and the extent of LOH correlated with PFS. LOH burden may indicate vulnerability to treatment targeting DNA repair, such as PARP1 inhibitors.

A comprehensive analysis of PAX8 expression in human epithelial tumors.

PAX8 is a paired-box gene important in embryogenesis of the thyroid, Müllerian, and renal/upper urinary tracts, and expression of PAX8 has been previously described in carcinomas from each of these sites. However, a large study including a wide variety of epithelial neoplasms from multiple organ sites other than the thyroid, kidney, or Müllerian system has not been performed. The goal of this study was to evaluate the utility of PAX8 immunostaining based on the evaluation of a wide range of epithelial tumors. PAX8 immunohistochemistry was performed on 1357 tumors (486 tumors in whole-tissue sections and 871 tumors in tissue microarrays, predominantly epithelial) from multiple organs. Only nuclear staining was scored as positive, and tumors were evaluated for the extent and intensity of staining. Western blot analysis with PAX8 was also performed on multiple tumor cell lines. Nuclear PAX8 staining was present in 91% (60 of 66) of thyroid tumors, 90% (158 of 176) of renal cell carcinomas (RCCs), 81% (13 of 16) of renal oncocytomas, 99% (164 of 165) of high-grade ovarian serous carcinomas, 71% (32 of 49) of nonserous ovarian epithelial neoplasms, 91% (10 of 11) of cervical epithelial lesions, and 98% (152 of 155) of endometrial adenocarcinomas. Of the remaining 719 evaluated tumors, only 30 cases (4%), including 12 thymic neoplasms, 3 bladder urothelial carcinomas, 4 lung squamous cell carcinomas, 2 esophageal adenocarcinomas, 1 pancreatic adenocarcinoma, 2 cholangiocarcinomas, 1 ovarian Sertoli-Leydig cell tumor, 1 ovarian sex cord stromal tumor, 3 testicular mixed germ cell tumors, and 1 acinic cell carcinoma, showed at least weak or focal PAX8 positivity. The unexpected finding was diffuse, moderate staining of PAX8 in a subset of thymomas and thymic carcinomas. The 689 remaining tumors, including but not limited to those from the prostate, colon, stomach, liver, adrenal gland, and head and neck, and small cell carcinomas from the lung, cervix, and ovary, were PAX8 negative. PAX8 specificity was confirmed by Western blot analysis, as expression was detected only in ovarian and RCC cell lines. These results show that PAX8 is a highly sensitive marker for thyroid, renal, Müllerian, and thymic tumors. Importantly, all lung adenocarcinomas, breast and adrenal neoplasms, and the majority of gastrointestinal tumors were negative for PAX8. Therefore, PAX8 is an excellent marker for confirming primary tumor site. In a subset of cases, additional markers, including but not limited to thyroid transcription factor-1, RCC, and Wilms tumor-1, may be needed to distinguish between the 3 most common PAX8-positive tumors.

An activated ErbB3/NRG1 autocrine loop supports in vivo proliferation in ovarian cancer cells.

Ovarian cancer is a leading cause of death from gynecologic malignancies. Treatment for advanced-stage disease remains limited and, to date, targeted therapies have been incompletely explored. By systematically suppressing each human tyrosine kinase in ovarian cancer cell lines by RNAi, we found that an autocrine signal-transducing loop involving NRG1 and activated ErbB3 operates in a subset of primary ovarian cancers and ovarian cancer cell lines. Perturbation of this circuit with ErbB3-directed RNAi decreased cell growth in three-dimensional culture and resulted in decreased disease progression and prolonged survival in a xenograft mouse model of ovarian cancer. Furthermore, a monoclonal ErbB3-directed antibody (MM-121) also significantly inhibited tumor growth in vivo. These findings identify ErbB3 as a potential therapeutic target in ovarian cancer.

Overexpression of elafin in ovarian carcinoma is driven by genomic gains and activation of the nuclear factor kappaB pathway and is associated with poor overall survival.

Ovarian cancer is a leading cause of cancer mortality in women. The aim of this study was to elucidate whether whey acidic protein (WAP) genes on chromosome 20q13.12, a region frequently amplified in this cancer, are expressed in serous carcinoma, the most common form of the disease. Herein, we report that a trio of WAP genes (HE4, SLPI, and Elafin) is overexpressed and secreted by serous ovarian carcinomas. To our knowledge, this is the first report linking Elafin to ovarian cancer. Fluorescence in situ hybridization analysis of primary tumors demonstrates genomic gains of the Elafin locus in a majority of cases. In addition, a combination of peptidomimetics, RNA interference, and chromatin immunoprecipitation experiments shows that Elafin expression can be transcriptionally upregulated by inflammatory cytokines through activation of the nuclear factor kappaB pathway. Importantly, using a clinically annotated tissue microarray composed of late-stage, high-grade serous ovarian carcinomas, we show that Elafin expression correlates with poor overall survival. These results, combined with our observation that Elafin is secreted by ovarian tumors and is minimally expressed in normal tissues, suggest that Elafin may serve as a determinant of poor survival in this disease.

Aberrations of p16INK4A, p14ARF and p15INK4B genes in pediatric solid tumors.

Expression of the p16INK4A (p16), p15INK4B (p15), and p14ARF genes, located at 9p21, was examined in pediatric neuroblastoma (NB), Ewing's sarcoma (ES), and rhabdomyosarcoma (RMS). p16 expression was absent in 4 of 5 ESs, and 2 of these 4 cases died. p16 expression was reduced or absent in 10 of 12 RMSs, and 4 of these 10 cases died. These results suggested the possibility that p16 expression was associated with the progression of ES and RMS. There has been no previous report on p14ARF in NB. Our investigation might indicate that abnormal expression of the p16 and p14ARF was associated with a poor prognosis in NB, although in some cases of NB normal p16 and abnormal p14ARF expression was seen. These findings suggest an important role of p14ARF gene in the tumorigenesis of NB. The different incidence of expression of the p16, p15, and p14ARF genes in these 3 tumor types may reflect differences of the molecular process through which the 3 tumors develop. Our results suggest that abnormal expression of the p16 and/or p14ARF may be associated with a poor prognosis in these 3 tumors.