Human ovarian surface epithelial cells immortalized with hTERT maintain functional pRb and p53 expression

Comparative Analysis of Primary Ovarian Cancer Cells and Established Cell Lines as a New Tool for Studies on Ovarian Cancer Cell Complexity

Primary cancer cells reflect the genetic background and phenotype of a tumor. Immortalized cells with higher proliferation activity have an advantage over primary cells. The aim of the study was to immortalize the primary ovarian cancer (OvCa) cells using the plasmid-carrying human telomerase reverse transcriptase (hTERT) gene and compare their phenotype and biological activity with the primary cells. The primary OvCa3 A and OvCa7 A cells were isolated from the ascitic fluid of two high-grade serous ovarian cancer patients and were characterized using immunocytochemical methods, flow cytometry, real-time RT-PCR, Western blot, metabolic activity, and migratory potential. Both immortalized ovarian cancer cell lines mirrored the phenotype of primary cancer cells, albeit with modifications. The OvCa3 A hTERT cells kept the mesenchymal stem cell phenotype of CD73/CD90/CD105-positivity and were CD133-negative, whereas the cell population of OvCa7 A hTERT lost CD73 expression, but almost 90% of cells expressed the CD133 characteristic for the CSCs phenotype. Immortalized OvCa cells differed in gene expression level with respect to Sox2 and Oct4, which was associated with stemness properties. The OvCa7 A hTERT cells showed higher metabolic and migratory activity and ALDH1 expression than the corresponding primary OvCa cells. Both primary and immortalized cell lines were able to form spheroids. The newly established unique immortalized cell line OvCa7 A hTERT, with the characteristic of a serous ovarian cancer malignancy feature, and with the accumulation of the p53, Pax8, and overexpression of the CD133 and CD44 molecules, may be a useful tool for research on therapeutic approaches, especially those targeting CSCs in ovarian cancer and in preclinical 2D and 3D models.

Replication stress and defective checkpoints make fallopian tube epithelial cells putative drivers of high-grade serous ovarian cancer

Clinical and molecular evidence indicates that high-grade serous ovarian cancer (HGSOC) primarily originates from the fallopian tube, not the ovarian surface. However, the reasons for this preference remain unclear. Our study highlights significant differences between fallopian tube epithelial (FTE) and ovarian surface epithelial (OSE) cells, providing the molecular basis for FTEs as site of origin of HGSOC. FTEs, unlike OSEs, exhibit heightened replication stress (RS), impaired repair of stalled forks, ineffective G2/M checkpoint, and increased tumorigenicity. BRCA1 heterozygosity exacerbates these defects, resulting in RS suppression haploinsufficiency and an aggressive tumor phenotype. Examination of human and mouse sections reveals buildup of the RS marker 53BP1 primarily in the fallopian tubes, particularly at the fimbrial ends. Furthermore, menopausal status influences RS levels. Our study provides a mechanistic rationale for FTE as the site of origin for HGSOC, investigates the impact of BRCA1 heterozygosity, and lays the groundwork for targeting early HGSOC drivers.

Comparative analysis of chlorambucil-induced DNA lesion formation and repair in a spectrum of different human cell systems

Chlorambucil (CLB) belongs to the class of nitrogen mustards (NMs), which are highly reactive bifunctional alkylating agents and were the first chemotherapeutic agents developed. They form DNA interstrand crosslinks (ICLs), which cause a blockage of DNA strand separation, inhibiting essential processes in DNA metabolism like replication and transcription. In fast replicating cells, e.g., tumor cells, this can induce cell death. The upregulation of ICL repair is thought to be a key factor for the resistance of tumor cells to ICL-inducing cytostatic agents including NMs. To monitor induction and repair of CLB-induced ICLs, we adjusted the automated reversed fluorometric analysis of alkaline DNA unwinding assay (rFADU) for the detection of ICLs in adherent cells. For the detection of monoalkylated DNA bases we established an LC-MS/MS method. We performed a comparative analysis of adduct formation and removal in five human cell lines and in peripheral blood mononuclear cells (PBMCs) after treatment with CLB. Dose-dependent increases in adduct formation were observed, and suitable treatment concentrations were identified for each cell line, which were then used for monitoring the kinetics of adduct formation. We observed significant differences in the repair kinetics of the cell lines tested. For example, in A2780 cells, hTERT immortalized VH10 cells, and in PBMCs a time-dependent repair of the two main monoalkylated DNA-adducts was confirmed. Regarding ICLs, repair was observed in all cell systems except for PBMCs. In conclusion, LC-MS/MS analyses combined with the rFADU technique are powerful tools to study the molecular mechanisms of NM-induced DNA damage and repair. By applying these methods to a spectrum of human cell systems of different origin and transformation status, we obtained insight into the cell-type specific repair of different CLB-induced DNA lesions, which may help identify novel resistance mechanisms of tumors and define molecular targets for therapeutic interventions.

Novel immortalized human vocal fold epithelial cell line: In vitro tool for mucosal biology

Study of vocal fold (VF) mucosal biology requires essential human vocal fold epithelial cell (hVFE) lines for use in appropriate model systems. We steadily transfected a retroviral construct containing human telomerase reverse transcriptase (hTERT) into primary normal hVFE to establish a continuously replicating hVFE cell line. Immortalized hVFE across passages have cobblestone morphology, express epithelial markers cytokeratin 4, 13 and 14, induced hTERT gene and protein expression, have similar RNAseq profiling, and can continuously grow for more than 8 months. DNA fingerprinting and karyotype analysis demonstrated that immortalized hVFE were consistent with the presence of a single cell line. Validation of the hVFE, in a three‐dimensional in vitro VF mucosal construct revealed a multilayered epithelial structure with VF epithelial cell markers. Wound scratch assay revealed higher migration capability of the immortalized hVFE on the surface of collagen‐fibronectin and collagen gel containing human vocal fold fibroblasts (hVFF). Collectively, our report demonstrates the first immortalized hVFE from true VFs providing a novel and invaluable tool for the study of epithelial cell‐fibroblast interactions that dictate disease and health of this specialized tissue.

Establishment of endometriotic models: the past and future

Endometriosis is a prevalent chronic disease that affects approximately 6% to 10% of reproductive-aged women. Although numerous researchers have endeavored to explore the etiology of endometriosis over a century, its etiology still remains an enigma. The exploration of pathophysiologic mechanism and novel therapy for endometriosis depends on ideal endometriotic models. In the previous decade, various endometriotic models have been established; therefore, we made a conclusion for available information on these models. This review summarized the common experimental models used in endometriotic studies, including their origins, characteristics, applications, and limitations. Endometriotic models played an important role in studying etiologies and novel treatments of endometriosis during the last decades. Among them, animal models and endometriotic cell lines were viewed as most common studying tools to explore the intrinsic entities of endometriosis. In addition, endometrial organoid also emerged and was regarded as an ideal studying tool for endometriosis research. Different research models collectively complement each other to advance the endometriosis research. The successful establishment of endometrial organoids means that organoids are expected to become an ideal model for studying endometriosis in the future.

Co-regulation and function of FOXM1/RHNO1 bidirectional genes in cancer

The FOXM1 transcription factor is an oncoprotein and a top biomarker of poor prognosis in human cancer. Overexpression and activation of FOXM1 is frequent in high-grade serous carcinoma (HGSC), the most common and lethal form of human ovarian cancer, and is linked to copy number gains at chromosome 12p13.33. We show that FOXM1 is co-amplified and co-expressed with RHNO1, a gene involved in the ATR-Chk1 signaling pathway that functions in the DNA replication stress response. We demonstrate that FOXM1 and RHNO1 are head-to-head (i.e., bidirectional) genes (BDG) regulated by a bidirectional promoter (BDP) (named F/R-BDP). FOXM1 and RHNO1 each promote oncogenic phenotypes in HGSC cells, including clonogenic growth, DNA homologous recombination repair, and poly-ADP ribosylase inhibitor resistance. FOXM1 and RHNO1 are one of the first examples of oncogenic BDG, and therapeutic targeting of FOXM1/RHNO1 BDG is a potential therapeutic approach for ovarian and other cancers.

Short-Form Thymic Stromal Lymphopoietin (sfTSLP) Is the Predominant Isoform Expressed by Gynaecologic Cancers and Promotes Tumour Growth

Simple Summary

Cytokines are a group of small proteins in the body that play an important part in boosting the immune system. Thymic stromal lymphopoietin (TSLP) is a cytokine that plays an important role in the maturation of T cells. Two variants of TSLP, long-form (lfTSLP) and short-form (sfTSLP), have been found, however their roles in cancers are not known. In this study, we discovered that sfTSLP, but not lfTSLP, is predominantly expressed in ovarian and endometrial cancers. The switch that turns the sfTSLP gene on or off is controlled by external modifications of DNA. Our results also found that sfTSLP promotes tumour growth through activating several signal pathways in cancer cells.

Abstract

Thymic stromal lymphopoietin (TSLP) is an epithelial cell derived cytokine belonging to the IL-7 family and a key initiator of allergic inflammation. Two main isoforms of TSLP, classified as long- (lfTSLP) and short-form (sfTSLP), have been reported in human, but their expression patterns and role(s) in cancers are not yet clear. mRNA expression was examined by isoform-specific RT-PCR and RNA in situ hybridisation. Epigenetic regulation was investigated by chromatin immunoprecipitation-PCR and bisulfite sequencing. Tumour progression was investigated by gene overexpression, cell viability assay, cancer organoid culture and transwell invasion. Signals were investigated by proteome profiler protein array and RNA-sequencing. With the use of isoform-specific primers and probes, we uncovered that only sfTSLP was expressed in the cell lines and tumour tissues of human ovarian and endometrial cancers. We also showed the epigenetic regulation of sfTSLP: sfTSLP transcription was regulated by histone acetylation at promoters in ovarian cancer cells, whereas silencing of the sfTSLP transcripts was regulated by promoter DNA methylation in endometrial cancer cells. In vitro study showed that ectopically overexpressing sfTSLP promoted tumour growth but not invasion. Human phosphokinase array application demonstrated that the sfTSLP overexpression activated phosphorylation of multiple intracellular kinases (including GSK3α/β, AMPKα1, p53, AKT1/2, ERK1/2 and Src) in ovarian cancer cells in a context-dependent manner. We further investigated the impact of sfTSLP overexpression on transcriptome by RNA-sequencing and found that EFNB2 and PBX1 were downregulated in ovarian and endometrial cancer cells, suggesting their role in sfTSLP-mediated tumour growth. In conclusion, sfTSLP is predominantly expressed in ovarian and endometrial cancers and promotes tumour growth.

Establishment of five immortalized human ovarian surface epithelial cell lines via SV40 T antigen or HPV E6/E7 expression

Background

Human ovarian surface epithelial (HOSE) cells are a critical cell source for ovarian cancer research; however, they are difficult to obtain and maintain under standard laboratory conditions in large quantities. The aim of this study was to generate immortalized HOSE (IHOSE) cells with maintained properties to the original cell source, thereby guaranteeing a sufficiently large cell quantity for ovarian cancer research.

Methods

HOSE cells isolated from four non-cancer patients and five IHOSE cell lines were established by induction of HPV-E6/E7 expression or SV40 large T antigen using a lenti-viral system. Each of IHOSE cells was confirmed to be distinct by STR profiling. RNA-sequencing was used to compare gene expression profiles in HOSE, IHOSE and ovarian cancer cells.

Results

RNA-sequencing results revealed a stronger linear correlation in gene expression between IHOSE and HOSE cells (R² = 0.9288) than between IHOSE or HOSE cells and ovarian cancer cells (R² = 0.8562 and R² = 0.7982, respectively). The gene expression pattern of 319 differentially expressed genes revealed minimal differences between HOSE and IHOSE cells, while a strong difference between ovarian cancer cells and HOSE or IHOSE cells was observed. Furthermore, the five IHOSE cell lines displayed morphological characteristics typical of epithelial cells but showed a lower level of EpCAM, CD133 and E-cadherin, as cancer stem marker, than ovarian cancer cells. Moreover, unlike cancer cells, IHOSE cells could not form colonies in the anchorage-independent soft agar growth assay.

Conclusion

These findings demonstrate that five newly established IHOSE cell lines have characteristics of progenitor HOSE cells while exhibiting continuous growth, and thus, should be highly useful as control cells for ovarian cancer research.

Immortalization of chicken embryonic liver-derived cell line by stable expression of hMRP18S-2 for serotype 4 fowl adenovirus propagation

Inclusion body hepatitis and hydropericardium-hepatitis syndrome caused by serotype 4 fowl adenovirus (FAdV-4) have emerged in China since 2013. FAdV is usually propagated in primary chicken embryonic liver cells or embryo yolk sac. The aim of this work was to develop an immortalized CEL cell line by stable expression of human mitochondrial ribosomal protein 18S-2, named CEL-hMRP18S-2 cells, for the propagation of FAdV-4. The maximum cell density of CEL-hMRP18S-2 cells could reach 2.65 × 10⁶ cells/ml in four-days culture. According to the mRNA levels of cell-cycle related genes in CEL-hMRP18S-2 cells tested by qRT-PCR, we speculated that the transformation of hMRP18S-2 into CEL cells caused the functional inactivation of p53 and the significant down-regulation of p15^INK4b might cause the hyperphosphorylated form of Rb, releasing E2F-1 factor and enhancing the E2F-dependent transcription for cell cycle progression. It was suspected that the up-regulated c-Myc mRNA level at the initial period of immortalization might prompt transformed cells through the G0-G1 checkpoint. The normal CPE was observed in CEL-hMRP18S-2 cells infected by FAdV-4 and microcarrier suspension culture performed for FAdV-4 propagation with 9.0 lgTCID₅₀/ml suggested that CEL-hMRP18S-2 cells could be a useful continuous cell line for isolation of wild FAdV and production of FAdV-inactivated vaccine.

Undermining ribosomal RNA transcription in both the nucleolus and mitochondrion: an offbeat approach to target MYC-driven cancer

The MYC transcription factor coordinates, via different RNA polymerases, the transcription of both ribosomal RNA (rRNA) and protein genes necessary for nucleolar as well as mitochondrial ribogenesis. In this study we tested if MYC-coordination of rRNA transcription in the nucleolus and in the mitochondrion drives (cancer) cell proliferation. Here we show that the anti-proliferative effect of CX-5461, a Pol I inhibitor of rRNA transcription, in ovarian (cancer) cell contexts characterized by MYC overexpression is enhanced either by 2'-C-Methyl Adenosine (2'-C-MeA), a ribonucleoside that inhibits POLRMT mitochondrial rRNA (mt-rRNA) transcription and doxycycline, a tetracycline known to affect mitochondrial translation. Thus, hindering not only mt-rRNA transcription, but also mitoribosome function in MYC-overexpressing ovarian (cancer) cells, potentiates the antiproliferative effect of CX-5461. Targeting MYC-regulated rRNA transcription and ribogenesis in both the nucleolus and mitochondrion seems to be a novel approach worth of consideration for treating MYC-driven cancer.

Overexpression of miRNA-221 promotes cell proliferation by targeting the apoptotic protease activating factor-1 and indicates a poor prognosis in ovarian cancer

MicroRNAs are a class of small non-coding, endogenous RNAs involved in cancer development and progression. MicroRNA-221 (mir-221) has been reported to have both an oncogenic and tumor-suppressive role in human tumors, but the role of miR-221 in ovarian cancer is poorly understood. In the present study, the expression levels of miR-221 and the apoptosis protease activating factor 1 (APAF1) protein in 63 samples of ovarian cancer tissues and the cell lines, IOSE25, A2780, OVCAR3, SKOV3 and 3AO were detected by quantitative reverse-transcription polymerase chain reaction (qRT-PCR) and western blot analysis, respectively. Cell proliferation was measured using Cell Counting kit-8 (CCK-8); cell migration and invasion were detected using a Transwell assay; cell apoptosis was evaluated by flow cytometry and Hoechst staining, and a luciferase assay was performed to verify a putative target site of miR-221 in the 3′-UTR of APAF1 mRNA. Expression of miR-221 was upregulated in ovarian cancer tissues. Patients with increased miR-221 expression levels had a reduced disease-free survival (P=0.0014) and overall survival (P=0.0058) compared with those with low miR-221 expression. Transfection of SKOV3 and A2780 cell lines with miR-221 inhibitor induced APAF1 protein expression, suppressed cell proliferation and migration and promoted tumor cell apoptosis. In conclusion, the APAF1 gene was confirmed as a direct target of miR-221 and overexpression of APAF1 suppressed ovarian cancer cell proliferation and induced cell apoptosis in vitro. These findings indicate that miR-221-APAF1 should be studied further as a potential new diagnostic or prognostic biomarker for ovarian cancer.

Decreased expression of long non-coding RNA GAS5 promotes cell proliferation, migration and invasion, and indicates a poor prognosis in ovarian cancer

Long non-coding RNA growth arrest-specific 5 (GAS5) was reported to be aberrantly expressed in various types of cancers. However, the role of GAS5 in the evolution and progression of ovarian cancer remains elusive. In the present study, we aimed to investigate the cellular function and clinical significance of GAS5 in ovarian cancer. GAS5 expression levels in 63 ovarian cancer tissues were detected by quantitative real-time PCR. Cell Counting Kit-8 (CCK-8) assay was performed to analyze the effect of GAS5 on cell proliferation. The effect of GAS5 on cell migration and invasion was detected using Transwell assay. Cell apoptosis was evaluated by flow cytometry and Hoechst staining. SKOV3 cells with stable expression of GAS5 were injected into nude mice to study the effect of GAS5 on tumorigenesis in vivo. Western blotting was used to determine the protein levels of GAS5 potential targets. The results showed that GAS5 was markedly decreased in tumor tissues and a lower expression of GAS5 was detected in tumors with larger size, deeper invasive depth and higher tumor stage. Patients with low GAS5 expression level had poorer disease-free (P<0.0001) and overall survival (P=0.0016) than those with high GAS5 expression. Moreover, overexpression of GAS5 was demonstrated to suppress ovarian cancer cell proliferation in vitro and in vivo. Finally, we found that GAS5 influenced ovarian cancer cell proliferation, partly via regulating cyclin D1, p21 and apoptosis protease activating factor 1 (APAF1) expression. Our findings suggest that lncRNA GAS5 may represent a novel indicator of poor prognosis in ovarian cancer and may be a potential therapeutic target for diagnosis and therapy.

Genetic determinants of FOXM1 overexpression in epithelial ovarian cancer and functional contribution to cell cycle progression

The FOXM1 transcription factor network is frequently activated in high-grade serous ovarian cancer (HGSOC), the most common and lethal subtype of epithelial ovarian cancer (EOC). We used primary human EOC tissues, HGSOC cell lines, mouse and human ovarian surface epithelial (OSE) cells, and a murine transgenic ovarian cancer model to investigate genetic determinants of FOXM1 overexpression in EOC, and to begin to define its functional contribution to disease pathology. The Cancer Genome Atlas (TCGA) data indicated that the FOXM1 locus is amplified in ~12% of HGSOC, greater than any other tumor type examined, and that FOXM1 amplification correlates with increased expression and poor survival. In an independent set of primary EOC tissues, FOXM1 expression correlated with advanced stage and grade. Of the three known FOXM1 isoforms, FOXM1c showed highest expression in EOC. In murine OSE cells, combined knockout of Rb1 and Trp53 synergistically induced FOXM1. Consistently, human OSE cells immortalized with SV40 Large T antigen (IOSE-SV) had significantly higher FOXM1 expression than OSE immortalized with hTERT (IOSE-T). FOXM1 was overexpressed in murine ovarian tumors driven by combined Rb1/Trp53 disruption. FOXM1 induction in IOSE-SV cells was partially dependent on E2F1, and FOXM1 expression correlated with E2F1 expression in human EOC tissues. Finally, FOXM1 functionally contributed to cell cycle progression and relevant target gene expression in human OSE and HGSOC cell models. In summary, gene amplification, p53 and Rb disruption, and E2F1 activation drive FOXM1 expression in EOC, and FOXM1 promotes cell cycle progression in EOC cell models.

Overexpression of microRNA-497 suppresses cell proliferation and induces apoptosis through targeting paired box 2 in human ovarian cancer

MicroRNAs are a class of endogenous, small non-coding RNAs which are tightly involved in evolution and progression of human cancers. MicroRNA-497 has been reported as tumor-suppressor in various human cancer. However, the role of miR-497 in ovarian cancer is still poorly known. We investigated the expression level and cellular function of miR-497 in human ovarian cancer. In this study, the expression of miR-497 in ovarian cancer tissues and SKOV3 cells was detected by quantitative reverse‑transcription polymerase chain reaction (qRT-PCR). CCK-8 assay was used to analysis the cell proliferation. Transwell assay was performed to analysis cell migration and invasion. Cell apoptosis was evaluated by flow cytometry. Luciferase assay was performed to verify a putative target site of miR-497 in the 3'UTR of PAX2 mRNA. The results showed that miR-497 was markedly decreased in ovarian cancer tissues and SKOV3 cells. Moreover, overexpression of miR-497 in SKOV3 cells induced PAX2 protein expression and resulted in inhibition of cell proliferation, migration and invasion, and induction of cell apoptosis. In addition, we confirmed that PAX2 is a direct target gene of miR-497. Furthermore, Silencing of PAX2 by RNA interference suppressed cell proliferation and promoted cell apoptosis in vitro. Taken together, our study rationally present that miR-497 has a potential role as a useful diagnostic and therapeutic biomarker for human ovarian cancer.

Src as a novel therapeutic target for endometriosis

BACKGROUND

Endometriosis is a common condition that is associated with an increased risk of developing ovarian carcinoma. Improved in vitro models of this disease are needed to better understand how endometriosis, a benign disease, can undergo neoplastic transformation, and for the development of novel treatment strategies to prevent this progression.

METHODS

We describe the generation and in vitro characterization of novel TERT immortalized ovarian endometriosis epithelial cell lines (EEC16-TERT).

RESULTS

Expression of TERT alone was sufficient to immortalize endometriosis epithelial cells. TERT immortalization induces an epithelial-to-mesenchymal transition and perturbation in the expression of genes involved in the development of ovarian cancer. EEC16-TERT was non-tumorigenic when xenografted into immunocompromised mice but grew in anchorage-independent growth assays in an epidermal growth factor and hydrocortisone dependent manner. Colony formation in agar was abolished by inhibition of Src, and the Src pathway was found to be activated in human endometriosis lesions.

CONCLUSIONS

This new in vitro model system mimics endometriosis and the early stages of neoplastic transformation in the development of endometriosis associated ovarian cancer. We demonstrate the potential clinical relevance of this model by identifying Src activation as a novel pathway in endometriosis that could be targeted therapeutically, perhaps as a novel strategy to manage endometriosis clinically, or to prevent the development of endometriosis-associated ovarian cancer.

Vaccinia virus induces programmed necrosis in ovarian cancer cells

The mechanisms by which oncolytic vaccinia virus induces tumor cell death are poorly understood. We have evaluated cell death pathways following infection of ovarian cancer cells with both wild-type and thymidine kinase-deleted (dTK) Lister strain vaccinia. We show that death does not rely upon classical apoptosis despite the appearances of some limited apoptotic features, including phosphatidylserine externalization and appearance of sub-G1 DNA populations. Vaccinia infection induces marked lipidation of LC3 proteins, but there is no general activation of the autophagic process and cell death does not rely upon autophagy induction. We show that vaccinia induces necrotic morphology on transmission electron microscopy, accompanied by marked by reductions in intracellular adenosine triphosphate, altered mitochondrial metabolism, and release of high mobility group box 1 (HMGB1) protein. This necrotic cell death appears regulated, as infection induces formation of a receptor interacting protein (RIP1)/caspase-8 complex. In addition, pharmacological inhibition of both RIP1 and substrates downstream of RIP1, including MLKL, significantly attenuate cell death. Blockade of TNF-α, however, does not alter virus efficacy, suggesting that necrosis does not result from autocrine cytokine release. Overall, these results show that, in ovarian cancer cells, vaccinia virus causes necrotic cell death that is mediated through a programmed series of events.

Modeling High-Grade Serous Carcinoma: How Converging Insights into Pathogenesis and Genetics are Driving Better Experimental Platforms

Recent developments in the study of epithelial ovarian cancer have called into question the traditional views regarding the site of tumor initiation. Histopathologic studies and genomic analyses suggest that extra-ovarian sites, like the fallopian tube, may harbor the coveted cell of origin and could therefore contribute significantly to the development of high-grade serous ovarian carcinoma (HG-SOC). Our ability to validate these emerging genomic and pathologic observations and characterize the early transformation events of HG-SOC hinges on the development of novel model systems. Currently, there are only a handful of new model systems that are addressing these concerns. This review will chronicle the convergent evolution of these ovarian cancer model systems in the context of the changing pathologic and genomic understanding of HG-SOC.

Oncolytic virotherapy for ovarian cancer

In the past two decades, more than 20 viruses with selective tropism for tumor cells have been developed as oncolytic viruses (OVs) for treatments of a variety of malignancies. Of these viruses, eleven have been tested in human ovarian cancer models in preclinical studies. So far, nine phase I or II clinical trials have been conducted or initiated using four different types of OVs in patients with recurrent ovarian cancers. In this article, we summarize the different OVs that are being assessed as therapeutics for ovarian cancer. We also present an overview of recent advances in identification of key genetic or immune-response pathways involved in tumorigenesis of ovarian cancer, which provides a better understanding of the tumor specificities and oncolytic properties of OVs. In addition, we discuss how next-generation OVs could be genetically modified or integrated into multimodality regimens to improve clinical outcomes based on recent advances in ovarian cancer biology.

Multiple inhibitory ligands induce impaired T-cell immunologic synapse function in chronic lymphocytic leukemia that can be blocked with lenalidomide: establishing a reversible immune evasion mechanism in human cancer

Cancer immune evasion is an emerging hallmark of disease progression. We have demonstrated previously that impaired actin polymerization at the T-cell immunologic synapse is a global immune dysfunction in chronic lymphocytic leukemia (CLL). Direct contact with tumor cells induces defective actin polarization at the synapse in previously healthy T cells, but the molecules mediating this dysfunction were not known. In the present study, we show via functional screening assays that CD200, CD270, CD274, and CD276 are coopted by CLL cells to induce impaired actin synapse formation in both allogeneic and autologous T cells. We also show that inhibitory ligand-induced impairment of T-cell actin dynamics is a common immunosuppressive strategy used by both hematologic (including lymphoma) and solid carcinoma cells. This immunosuppressive signaling targets T-cell Rho-GTPase activation. Of clinical relevance, the immunomodulatory drug lenalidomide prevented the induction of these defects by down-regulating tumor cell-inhibitory molecule expression. These results using human CLL as a model cancer establish a novel evasion mechanism whereby malignant cells exploit multiple inhibitory ligand signaling to down-regulate small GTPases and lytic synapse function in global T-cell populations. These findings should contribute to the design of immunotherapeutic strategies to reverse T-cell tolerance in cancer.

Sequential genetic change at the TP53 and chemokine receptor CXCR4 locus during transformation of human ovarian surface epithelium

Early genetic events in the development of high-grade serous ovarian cancer, HGSOC, may define the molecular basis of the profound structural and numerical instability of chromosomes in this disease. To discover candidate genetic changes we sequentially passaged cells from a karyotypically normal hTERT immortalised human ovarian surface epithelial line (IOSE25) resulting in the spontaneous formation of colonies in soft agar. Cell lines (TOSE 1 and 4) established from these colonies had an abnormal karyotype and altered morphology but were not tumorigenic in immunodeficient mice.

TOSE cells showed loss of heterozygosity at TP53, increased nuclear p53 immunoreactivity and altered expression profile of p53 target genes. The parental IOSE25 cells contained a missense, heterozygous R175H mutation in TP53 whereas TOSE cells had loss of heterozygosity at the TP53 locus with a new R273H mutation at the previous wild-type TP53 allele.

Cytogenetic and array CGH analysis of TOSE cells also revealed a focal genomic amplification of CXCR4, a chemokine receptor commonly expressed by HGSOC cells. TOSE cells had increased functional CXCR4 protein and its abrogation reduced epidermal growth factor receptor, EGFR, expression, as well as colony size and number. The CXCR4 ligand, CXCL12, was epigenetically silenced in TOSE cells and its forced expression increased TOSE colony size. TOSE cells had other cytogenetic changes typical of those seen in HGSOC ovarian cancer cell lines and biopsies. In addition, enrichment of CXCR4 pathway in expression profiles from HGSOC correlated with enrichment of a mutated TP53 gene expression signature and of EGFR pathway genes.

Our data suggest that mutations in TP53 and amplification of the CXCR4 gene locus may be early events in the development of HGSOC, and associated with chromosomal instability.

Microcell-mediated chromosome transfer identifies EPB41L3 as a functional suppressor of epithelial ovarian cancers

We used a functional complementation approach to identify tumor-suppressor genes and putative therapeutic targets for ovarian cancer. Microcell-mediated transfer of chromosome 18 in the ovarian cancer cell line TOV21G induced in vitro and in vivo neoplastic suppression. Gene expression microarray profiling in TOV21G(+18) hybrids identified 14 candidate genes on chromosome 18 that were significantly overexpressed and therefore associated with neoplastic suppression. Further analysis of messenger RNA and protein expression for these genes in additional ovarian cancer cell lines indicated that EPB41L3 (erythrocyte membrane protein band 4.1-like 3, alternative names DAL-1 and 4.1B) was a candidate ovarian cancer-suppressor gene. Immunoblot analysis showed that EPB41L3 was activated in TOV21G(+18) hybrids, expressed in normal ovarian epithelial cell lines, but was absent in 15 (78%) of 19 ovarian cancer cell lines. Using immunohistochemistry, 66% of 794 invasive ovarian tumors showed no EPB41L3 expression compared with only 24% of benign ovarian tumors and 0% of normal ovarian epithelial tissues. EPB41L3 was extensively methylated in ovarian cancer cell lines and primary ovarian tumors compared with normal tissues (P = .00004), suggesting this may be the mechanism of gene inactivation in ovarian cancers. Constitutive reexpression of EPB41L3 in a three-dimensional multicellular spheroid model of ovarian cancer caused significant growth suppression and induced apoptosis. Transmission and scanning electron microscopy demonstrated many similarities between EPB41L3-expressing cells and chromosome 18 donor-recipient hybrids, suggesting that EPB41L3 is the gene responsible for neoplastic suppression after chromosome 18 transfer. Finally, an inducible model of EPB41L3 expression in three-dimensional spheroids confirmed that reexpression of EPB41L3 induces extensive apoptotic cell death in ovarian cancers.

Telomerase in the ovary

Telomerase, an enzyme complex that binds the chromosome ends (telomeres) and maintains telomere length and integrity, is present in germ cells, proliferative granulosa cells, germline stem cells, and neoplastic cells in the ovary, but it is absent in differentiated or aged cells. Activation of telomerase in the ovary underpins both benign and malignant cell proliferation in several compartments, including the germ cells, membrana granulosa, and the ovarian surface epithelium. The difference in telomerase operation between normal and abnormal cell proliferations may lie in the mechanisms of telomerase activation in a deregulated manner. Recent studies have implicated telomerase activity in ovarian cancer as well as oogenesis and fertility. Inhibition of telomerase and the shortening of telomeres are seen in occult ovarian insufficiency. Studies of how telomerase operates and regulates ovary development may provide insight into the development of both germ cells for ovarian reproductive function and neoplastic cells in ovarian cancer. The current review summarizes the roles of telomerase in the development of oocytes and proliferation of granulosa cells during folliculogenesis and in the process of tumorigenesis. It also describes the regulation of telomerase by estrogen in the ovary.

p21 Promotes oncolytic adenoviral activity in ovarian cancer and is a potential biomarker

The oncolytic adenovirus dl922-947 replicates selectively within and lyses cells with a dysregulated Rb pathway, a finding seen in > 90% human cancers. dl922-947 is more potent than wild type adenovirus and the E1B-deletion mutant dl1520 (Onyx-015). We wished to determine which host cell factors influence cytotoxicity. SV40 large T-transformed MRC5-VA cells are 3-logs more sensitive to dl922-947 than isogenic parental MRC5 cells, confirming that an abnormal G1/S checkpoint increases viral efficacy. The sensitivity of ovarian cancer cells to dl922-947 varied widely: IC₅₀ values ranged from 51 (SKOV3ip1) to 0.03 pfu/cell (TOV21G). Cells sensitive to dl922-947 had higher S phase populations and supported earlier E1A expression. Cytotoxicity correlated poorly with both infectivity and replication, but well with expression of p21 by microarray and western blot analyses. Matched p21+/+ and -/- Hct116 cells confirmed that p21 influences dl922-947 activity in vitro and in vivo. siRNA-mediated p21 knockdown in sensitive TOV21G cells decreases E1A expression and viral cytotoxicity, whilst expression of p21 in resistant A2780CP cells increases virus activity in vitro and in intraperitoneal xenografts. These results highlight that host cell factors beyond simple infectivity can influence the efficacy of oncolytic adenoviruses. p21 expression may be an important biomarker of response in clinical trials.

Senescent fibroblasts promote neoplastic transformation of partially transformed ovarian epithelial cells in a three-dimensional model of early stage ovarian cancer

Most epithelial ovarian cancers are diagnosed postmenopausally, although the well-established epidemiological risk factors (parity, oral contraceptive use) are premenopausal. We hypothesized that accumulation of senescent fibroblasts, together with concomitant loss of presenescent fibroblasts within the ovarian cortex, promotes initiation and early development of ovarian cancer from ovarian surface epithelial (OSE) cells. To test this, we established immortalized OSE (IOSE) cell lines that mimic early neoplastic transformation by overexpressing the CMYC oncogene (IOSE(CMYC)) and normal ovarian presenescent (PSN) and senescent (SEN) fibroblast cell lines. We then evaluated the ability of PSN and SEN fibroblasts to transform IOSE and IOSE(CMYC) after coculture. SEN fibroblasts significantly enhanced neoplastic development of IOSE(CMYC) cells; there was an up to 15-fold increase in migration of IOSE(CMYC) cells cocultured with SEN fibroblasts compared with PSN fibroblasts. Conditioned medium from SEN fibroblasts promoted anchorage-independent growth of IOSE(CMYC) cells. We studied fibroblast-epithelial cell interactions in heterotypic three-dimensional spheroid models. Dual immunohistochemical staining of spheroids for a proliferation marker (MIB-1) and cytokeratin-18 indicated that SEN fibroblasts induce approximately a five-fold increase in proliferation of IOSE(CMYC) cells relative to cocultures with PSN fibroblasts. SEN, but not PSN fibroblasts, also induced nuclear atypia in epithelial cells in three-dimensional spheroids. These data suggest for the first time that the accumulation of senescent, or loss of presenescent fibroblasts, can promote neoplastic development of partially transformed OSE cells in vitro and illustrates the power of using three-dimensional heterotypic modeling to gain better insights into the etiology underlying the development of epithelial ovarian cancer.

Inflammatory cytokine tumor necrosis factor alpha confers precancerous phenotype in an organoid model of normal human ovarian surface epithelial cells

In this study, we established an in vitro organoid model of normal human ovarian surface epithelial (HOSE) cells. The spheroids of these normal HOSE cells resembled epithelial inclusion cysts in human ovarian cortex, which are the cells of origin of ovarian epithelial tumor. Because there are strong correlations between chronic inflammation and the incidence of ovarian cancer, we used the organoid model to test whether protumor inflammatory cytokine tumor necrosis factor alpha would induce malignant phenotype in normal HOSE cells. Prolonged treatment of tumor necrosis factor alpha induced phenotypic changes of the HOSE spheroids, which exhibited the characteristics of precancerous lesions of ovarian epithelial tumors, including reinitiation of cell proliferation, structural disorganization, epithelial stratification, loss of epithelial polarity, degradation of basement membrane, cell invasion, and overexpression of ovarian cancer markers. The result of this study provides not only an evidence supporting the link between chronic inflammation and ovarian cancer formation but also a relevant and novel in vitro model for studying of early events of ovarian cancer.

Organotypic culture model of pancreatic cancer demonstrates that stromal cells modulate E-cadherin, beta-catenin, and Ezrin expression in tumor cells

Pancreatic cancer is characterized by an intense stromal reaction. Reproducible three-dimensional in vitro systems for exploring interactions of the stroma with pancreatic cancer cells have not previously been available, prompting us to develop such a model. Cancer cells were grown on collagen/Matrigel and embedded with or without stromal cells (hTERT-immortalized human PS-1 stellate cells or MRC-5 fibroblasts) for 7 days. Proliferation and apoptosis, as well as important cell-cell adhesion and cytoskeleton-regulating proteins, were studied. PS-1 cells were confirmed as stellate based on the expression of key cytoskeletal proteins and lipid vesicles. Capan-1, and to a lesser extent PaCa-3, cells differentiated into luminal structures, exhibiting a central apoptotic core with a proliferating peripheral rim and an apico-basal polarity. Presence of either stromal cell type translocated Ezrin from apical (when stromal cells were absent) to basal aspects of cancer cells, where it was associated with invasive activity. Interestingly, the presence of 'normal' (not tumor-derived) stromal cells induced total tumor cell number reduction (P < 0.005) associated with a significant decrease in E-cadherin expression (P < 0.005). Conversely, beta-catenin expression was up-regulated (P < 0.01) in the presence of stromal cells with predominant cytoplasmic expression. Moreover, patient samples confirmed that these data recapitulated the clinical situation. In conclusion, pancreatic organotypic culture offers a reproducible, bio-mimetic, three-dimensional in vitro model that allows examination of the interactions between stromal elements and pancreatic cancer cells.

An antagonist of the chemokine receptor CXCR4 induces mitotic catastrophe in ovarian cancer cells

The chemokine receptor CXCR4 is expressed by malignant cells in ovarian cancer and is implicated in their growth and spread. We report here a unique mechanism of action of a small peptide antagonist of CXCR4 on ovarian cancer cells: induction of cell death by mitotic catastrophe. CTCE-9908 inhibited ovarian cancer cell migration to CXCL12, but on longer incubation, caused cell death in CXCR4-positive cells. CTCE-9908 did not cause apoptosis or cellular senescence, but induced multinucleation, G(2)-M arrest, and abnormal mitosis in ovarian cancer cells. This suggests that cell death was caused by mitotic catastrophe. Using microarray and Western blot analysis, we showed that CTCE-9908 deregulated DNA damage checkpoint proteins and spindle assembly checkpoint proteins at G(2)-M phases of the cell cycle. Combination treatment of CTCE-9908 and the drug paclitaxel led to an additive cytotoxicity that also involved mitotic catastrophe. We conclude that CTCE-9908 has a unique mechanism of action in ovarian cancer cells that seems to be CXCR4 specific.

Functional complementation studies identify candidate genes and common genetic variants associated with ovarian cancer survival

Common germline genetic variation and/or somatic alterations in tumours may be associated with survival in women diagnosed with ovarian cancer. The successful identification of genetic associations relies on a suitable strategy for identifying and testing candidate genes. We used microcell-mediated chromosome transfer approach and expression microarray analysis to identify genes that were associated with neoplastic suppression in ovarian cancer cell lines. Sixty-five tagging single nucleotide polymorphisms (tSNPs) in nine candidate genes were genotyped in approximately 1700 invasive ovarian cancer cases to look for associations with survival. For two of these genes, loss of heterozygosity (LOH) analysis of tSNPs in 314 ovarian tumours was used to identify associations between somatic gene deletions and survival. We identified significant associations with survival for a tSNP in caspase 5 (CASP5) [hazard ratio (HR) = 1.13 (95% CI: 1.00-1.27), P = 0.042] and two tSNPs in the retinoblastoma binding protein (RBBP8) gene [HR = 0.85 (95% CI: 0.75-0.95), P = 0.007 and HR = 0.83 (95% CI: 0.71-0.95), P = 0.009]. After adjusting for multiple prognostic factors in a multivariate Cox regression analysis, both associations in RBBP8 remained significant (P = 0.028 and 0.036). We then genotyped 314 ovarian tumours for several tSNPs in CASP5 and RBBP8 to identify gene deletions by LOH. For RBBP8, 35% of tumours in 101 informative cases showed somatic allelic deletion; LOH of RBBP8 was associated with a significantly worse prognosis [HR = 2.19 (95% CI: 1.36-3.54), P = 0.001]. In summary, a novel in vitro functional approach in ovarian cancer cells has identified RBBP8 as a gene for which both germline genetic variation and somatic alterations in tumours are associated with survival in ovarian cancer patients.

A novel function of colony-stimulating factor 1 receptor in hTERT immortalization of human epithelial cells

The receptor for macrophage colony-stimulating factor 1 receptor (CSF1R) is a product of the proto-oncogene c-fms and a member of the class III transmembrane tyrosine kinase receptor family. Earlier, we described increased mRNA expression of CSF1R in human telomerase reverse transcriptase (hTERT) immortalized human ovarian surface epithelial (IOSE) cell lines derived from a single donor. Here, we further describe that CSF1R is upregulated at both the mRNA and protein level in hTERT immortalized human normal OSE cells from two different donors and in hTERT immortalized human pancreatic ductal epithelial cells. CSF1R was not upregulated in hTERT immortalized epithelial clones that subsequently underwent senescence or in immortalized fibroblasts. Upon stimulation by the CSF1R ligand CSF1, the immortalized epithelial cell lines showed rapid internalization of CSF1R with concomitant down-modulation and colocalization of phosphorylated NFkappaBp65 with hTERT protein, hTERT translocation into the nucleus and the binding of c-Myc to the hTERT promoter region. Reducing the expression of CSF1R using short hairpin interfering RNA abolished these effects and also decreased cell survival and the number of population doublings under suboptimal culture conditions. The telomerase inhibitor GRN163L confirmed a role for telomerase in the cleavage of the intracellular domain of CSF1R. On the basis of these findings, we suggest that CSF1R may be a critical factor facilitating hTERT immortalization of epithelial cells.