NLRC5 overexpression in ovarian tumors remodels the tumor microenvironment and increases T-cell reactivity toward autologous tumor-associated antigens

Introduction

Epithelial ovarian cancer (OC) stands as one of the deadliest gynecologic malignancies, urgently necessitating novel therapeutic strategies. Approximately 60% of ovarian tumors exhibit reduced expression of major histocompatibility complex class I (MHC I), intensifying immune evasion mechanisms and rendering immunotherapies ineffective. NOD-like receptor CARD domain containing 5 (NLRC5) transcriptionally regulates MHC I genes and many antigen presentation machinery components. We therefore explored the therapeutic potential of NLRC5 in OC.

Methods

We generated OC cells overexpressing NLRC5 to rescue MHC I expression and antigen presentation and then assessed their capability to respond to PD-L1 blockade and an infected cell vaccine.

Results

Analysis of microarray datasets revealed a correlation between elevated NLRC5 expression and extended survival in OC patients; however, NLRC5 was scarcely detected in the OC tumor microenvironment. OC cells overexpressing NLRC5 exhibited slower tumor growth and resulted in higher recruitment of leukocytes in the TME with lower CD4/CD8 T-cell ratios and increased activation of T cells. Immune cells from peripheral blood, spleen, and ascites from these mice displayed heightened activation and interferon-gamma production when exposed to autologous tumor-associated antigens. Finally, as a proof of concept, NLRC5 overexpression within an infected cell vaccine platform enhanced responses and prolonged survival in comparison with control groups when challenged with parental tumors.

Discussion

These findings provide a compelling rationale for utilizing NLRC5 overexpression in "cold" tumor models to enhance tumor susceptibility to T-cell recognition and elimination by boosting the presentation of endogenous tumor antigens. This approach holds promise for improving antitumoral immune responses in OC.

PAX2 induces vascular‑like structures in normal ovarian cells and ovarian cancer

In adult tissue, the paired box 2 (PAX2) protein is expressed in healthy oviductal, but not normal ovarian surface epithelial cells. PAX2 is expressed in a subset of cases of serous ovarian carcinoma; however, the role of PAX2 in the initiation and progression of ovarian cancer remains unknown. The aim of the present study was to determine the biological effects of PAX2 expression in normal and cancerous epithelial cells. By culturing the normal and cancerous ovarian cells that express PAX2 in 3D culture and staining the cells with vasculogenic mimicry markers such as CD31 and PAS, it was shown that PAX2 overexpression in both normal and cancerous ovarian epithelial cells induced formation of vascular-like structures both in vitro and in vivo. These results indicated a potential role of PAX2 in ovarian cancer progression by increasing the presence of vascular-like structures to promote the supply of nutrients to tumor cells and facilitate cancer cell proliferation and invasion.

PAX2 promotes epithelial ovarian cancer progression involving fatty acid metabolic reprogramming

Ovarian cancer is the fifth most common type of cancer afflicting women and frequently presents at a late stage with a poor prognosis. While paired box 2 (PAX2) expression is frequently lost in high-grade serous ovarian cancer, it is expressed in a subset of ovarian tumors and may play a role in tumorigenesis. This study investigated the expression of PAX2 in ovarian cancer. The expression of PAX2 in a murine allograft model of ovarian cancer, the RM model, led to a more rapidly growing cell line both in vitro and in vivo. This finding was in accordance with the shorter progression-free survival observed in patients with a higher PAX2 expression, as determined in this study cohort by immunohistochemistry. iTRAQ-based proteomic profiling revealed that proteins involved in fatty acid metabolism and oxidative phosphorylation were found to be upregulated in RM tumors expressing PAX2. The expression of two key fatty acid metabolic genes was also found to be upregulated in PAX2-expressing human ovarian cancer samples. The analysis of existing datasets also indicated that a high expression of key enzymes in fatty acid metabolism was associated with a shorter progression-free survival time in patients with serous ovarian cancer. Thus, on the whole, the findings of this study indicate that PAX2 may promote ovarian cancer progression, involving fatty acid metabolic reprograming.

GREB1 is an estrogen receptor-regulated tumour promoter that is frequently expressed in ovarian cancer

Estrogenic hormone replacement therapy increases the risk of developing ovarian cancer, and estrogen promotes tumour initiation and growth in mouse models of this disease. GREB1 (Growth regulation by estrogen in breast cancer 1) is an ESR1 (estrogen receptor 1)-upregulated protein which may mediate estrogen action. GREB1 knockdown prevents hormone-driven proliferation of several breast and prostate cancer cell lines and prolongs survival of mice engrafted with ovarian cancer cells, but its mechanism of action remains unclear. In this study, we explored GREB1 function in ovarian cancer. GREB1 overexpression in ovarian cancer cell lines increased cell proliferation and migration and promoted a mesenchymal morphology associated with increased Col1a2, which encodes a collagen I subunit. GREB1 knockdown inhibited proliferation and promoted an epithelial morphology associated with decreased Col1a2. In human tissues, GREB1 was expressed in all ESR1-expressing tissues throughout the normal female reproductive tract, in addition to several tissues that did not show ESR1 expression. In a TMA of ovarian cancer cases, GREB1 was expressed in 75–85% of serous, endometrioid, mucinous, and clear cell carcinomas. Serous, endometrioid, and mucinous ovarian cancers were almost always positive for either ESR1 or GREB1, suggesting a possible reliance on signalling through ESR1 and/or GREB1. Targeting GREB1 may inhibit tumour-promoting pathways both downstream and independent of ESR1 and is therefore a possible treatment strategy worthy of further investigation.

PAX2 maintains the differentiation of mouse oviductal epithelium and inhibits the transition to a stem cell-like state

Recent studies have provided evidence that the secretory cells of the fallopian tube (oviduct) are a probable origin for high-grade serous ovarian carcinoma. In addition to secretory cells, the fallopian tube epithelium consists of ciliated cells and CD44+ undifferentiated stem-like cells. Loss of PAX2 expression is recognized as an early event in epithelial transformation, but the specific role of PAX2 in this transition is unknown. The aim of this study was to define the role of PAX2 in oviductal epithelial (OVE) cells and its response to transforming growth factor β1 (TGFβ), characterizing specifically its potential involvement in regulating stem cell-like behaviors that may contribute to formation of cancer-initiating cells. Treatment of primary cultures of mouse OVE cells with TGFβ induced an epithelial-mesenchymal transition (EMT) associated with decreased expression of PAX2 and an increase in the fraction of cells expressing CD44. PAX2 knockdown in OVE cells and overexpression in ovarian epithelial cells confirmed that PAX2 inhibits stem cell characteristics and regulates the degree of epithelial differentiation of OVE cells. These results suggest that loss of PAX2, as occurs in serous tubal intraepithelial carcinomas, may shift secretory cells to a more mesenchymal phenotype associated with stem-like features.

Enhancing Expression of Functional Human Sodium Iodide Symporter and Somatostatin Receptor in Recombinant Oncolytic Vaccinia Virus for In Vivo Imaging of Tumors

Oncolytic virus (OV) therapy has emerged as a novel tool in our therapeutic arsenals for fighting cancer. As a live biologic agent, OV has the ability to target and selectively amplify at the tumor sites. We have reported that a vaccinia-based OV (Pexa-Vec) has shown good efficacy in preclinical models and in clinical trials. To give an additional tool to clinicians to allow both treatment of the tumor and improved visualization of tumor margins, we developed new viral-based platforms with 2 specific gene reporters.

METHODS

We incorporated the human sodium iodide symporter (hNIS) and the human somatostatin receptor 2 (hSSR2) in the vaccinia-based OV and tested viral constructs for their abilities to track and treat tumor development in vivo.

RESULTS

Early and high-level expression of hNIS is detrimental to the recombinant virus, leading to the aggregation of hNIS protein and early cell death. Putting hNIS under a late synthetic promoter allowed a higher functional expression of the protein and much stronger ¹²³I or ⁹⁹Tc uptake. In vivo, the hNIS-containing virus infected and amplified in the tumor site, showing a better efficacy than the parental virus. The hNIS expression at the tumor site allowed for the imaging of viral infection and tumor regression. Similarly, hSSR2-containing OV vaccinia infected and lysed cancer cells.

CONCLUSION

When tumor-bearing mice were given hNIS- and hSSR2-containing OV, ⁹⁹Tc and ¹¹¹In signals coalesced at the tumor, highlighting the power of using these viruses for tumor diagnosis and treatment.

Microtubule disruption synergizes with oncolytic virotherapy by inhibiting interferon translation and potentiating bystander killing

In this study, we show that several microtubule-destabilizing agents used for decades for treatment of cancer and other diseases also sensitize cancer cells to oncolytic rhabdoviruses and improve therapeutic outcomes in resistant murine cancer models. Drug-induced microtubule destabilization leads to superior viral spread in cancer cells by disrupting type I IFN mRNA translation, leading to decreased IFN protein expression and secretion. Furthermore, microtubule-destabilizing agents specifically promote cancer cell death following stimulation by a subset of infection-induced cytokines, thereby increasing viral bystander effects. This study reveals a previously unappreciated role for microtubule structures in the regulation of the innate cellular antiviral response and demonstrates that unexpected combinations of approved chemotherapeutics and biological agents can lead to improved therapeutic outcomes.

Epithelial ovarian cancer stem cells: underlying complexity of a simple paradigm

The lack of significant progress in the treatment of epithelial ovarian cancer (EOC) underscores the need to gain a better understanding of the processes that lead to chemoresistance and recurrence. The cancer stem cell (CSC) hypothesis offers an attractive explanation of how a subpopulation of cells within a patient's tumour might remain refractory to treatment and subsequently form the basis of recurrent chemoresistant disease. This review examines the literature defining somatic stem cells of the ovary and fallopian tube, two tissues that give rise to EOC. In addition, considerable research has been reviewed, that has identified subpopulations of EOC cells, based on marker expression (CD133, CD44, CD117, CD24, epithelial cell adhesion molecule, LY6A, ALDH1 and side population (SP)), which are enriched for tumour initiating cells (TICs). While many studies identified either CD133 or CD44 as markers useful for enriching for TICs, there is little consensus. This suggests that EOC cells may have a phenotypic plasticity that may preclude the identification of universal markers defining a CSC. The assay that forms the basis of quantifying TICs is the xenograft assay. Considerable controversy surrounds the xenograft assay and it is essential that some of the potential limitations be examined in this review. Highlighting such limitations or weaknesses is required to properly evaluate data and broaden our interpretation of potential mechanisms that might be contributing to the pathogenesis of ovarian cancer.

A new spontaneously transformed syngeneic model of high-grade serous ovarian cancer with a tumor-initiating cell population

Improving screening and treatment options for patients with epithelial ovarian cancer has been a major challenge in cancer research. Development of novel diagnostic and therapeutic approaches, particularly for the most common subtype, high-grade serous ovarian cancer (HGSC), has been hampered by controversies over the origin of the disease and a lack of spontaneous HGSC models to resolve this controversy. Over long-term culture in our laboratory, an ovarian surface epithelial (OSE) cell line spontaneously transformed OSE (STOSE). The objective of this study was to determine if the STOSE cell line is a good model of HGSC. STOSE cells grow faster than early passage parental M0505 cells with a doubling time of 13 and 48 h, respectively. STOSE cells form colonies in soft agar, an activity for which M0505 cells have negligible capacity. Microarray analysis identified 1755 down-regulated genes and 1203 up-regulated genes in STOSE compared to M0505 cells, many associated with aberrant Wnt/β-catenin and Nf-κB signaling. Upregulation of Ccnd1 and loss of Cdkn2a in STOSE tumors is consistent with changes identified in human ovarian cancers by The Cancer Genome Atlas. Intraperitoneal injection of STOSE cells into severe combined immunodeficient and syngeneic FVB/N mice produced cytokeratin+, WT1+, inhibin-, and PAX8+ tumors, a histotype resembling human HGSC. Based on evidence that a SCA1+ stem cell-like population exists in M0505 cells, we examined a subpopulation of SCA1+ cells that is present in STOSE cells. Compared to SCA1- cells, SCA1+ STOSE cells have increased colony-forming capacity and form palpable tumors 8 days faster after intrabursal injection into FVB/N mice. This study has identified the STOSE cells as the first spontaneous murine model of HGSC and provides evidence for the OSE as a possible origin of HGSC. Furthermore, this model provides a novel opportunity to study how normal stem-like OSE cells may transform into tumor-initiating cells.

Technical challenges and limitations of current mouse models of ovarian cancer

The development of genetically engineered models (GEM) of epithelial ovarian cancer (EOC) has been very successful, with well validated models representing high grade and low grade serous adenocarcinomas and endometrioid carcinoma (EC). Most of these models were developed using technologies intended to target the ovarian surface epithelium (OSE), the cell type long believed to be the origin of EOC. More recent evidence has highlighted what is likely a more prevalent role of the secretory cell of the fallopian tube in the ontogeny of EOC, however none of the GEM of EOC have demonstrated successful targeting of this important cell type.

The precise technologies exploited to develop the existing GEM of EOC are varied and carry with them advantages and disadvantages. The use of tissue specific promoters to model disease has been very successful, but the lack of any truly specific OSE or oviductal secretory cell promoters makes the outcomes of these models quite unpredictable. Effecting genetic change by the administration of adenoviral vectors expressing Cre recombinase may alleviate the perceived need for tissue specific promoters, however the efficiencies of infection of different cell types is subject to numerous biological parameters that may lead to preferential targeting of certain cell populations.

One important future avenue of GEM of EOC is the evaluation of the role of genetic modifiers. We have found that genetic background can lead to contrasting phenotypes in one model of ovarian cancer, and data from other laboratories have also hinted that the exact genetic background of the model may influence the resulting phenotype. The different genetic backgrounds may modify the biology of the tumors in a manner that will be relevant to human disease, but they may also be modifying parameters which impact the response of the host to the technologies employed to develop the model.

Abstract 2907: Novel liposomal compositions of PharmaGap's lead peptide: Effect on ovarian cancer cell proliferation and signaling pathways

Background: Liposomes, vesicular structures in the nano - micrometer range, have been widely studied as drug delivery vehicles. Liposomes can self-assemble in aqueous solutions and are normally comprised of lipids organized in concentric bilayers that enclose an internal aqueous volume, unique in their ability to accommodate a wide variety of therapeutic or diagnostic compounds. Novel liposomal compositions of peptide GAP-107B8, have recently been developed and their inhibitory effect on cell proliferation in cancer cell lines has been studied. Protein kinase B, Akt, has been implicated in certain cancer functions, including cell motility and invasion, hormone independence, chemotherapy and radiation resistance. Abnormalities in Akt are associated with certain breast, pancreatic, colorectal, gastric and ovarian cancers. The present work shows that an important mechanism of action for GAP-107B8 peptide formulations is through modification of protein kinase pathways. Objectives: 1) To optimize GAP-107B8 liposomal formulations, 2) To evaluate the efficacy of GAP-107B8 liposomal formulations towards inhibiting proliferation in ovarian cancer cell lines and 3) To gather information on the inhibitory mechanism of action in ovarian cancer cells. Methods: Optimization of the lipid components in the liposomes including lipid identity and ratio in relation to extent of peptide-liposome association was determined by IEC, liposome size and charge. Cell proliferation was measured in A2780cp and OCC-1 ovarian cancer cell lines with liposomal peptide formulations (24 and 72 hrs). Immunoblotting experiments were executed on cancer cell line lysates treated with peptide to explore inhibitory effects on signaling targets. Results: Peptide association ranged from 80-100% for liposomal formulations prepared with two lipid components in varying ratios (formulation 2A and 2B) as opposed to a single lipid component (formulation 1 - 30%). Treatment of ovarian cancer cells with liposomal formulations 2A, 2B and 3 showed significant inhibition on cell proliferation when compared to control groups. Densitometry results showed a 50% reduction in pAkt levels (relative to Akt levels) when ovarian cells were treated with peptide for 1 hour (similar inhibitory effect found after peptide treatment for 4, 8, 14 and 30 hours). Conclusions: A lipid based delivery system for GAP-107B8 peptide was developed in which lipid ratio played an important role for an enhanced peptide-associated liposomal formulation. Proliferation results indicate that administration of peptides in liposome formulations generally results in improved potency in a time dependent manner. All formulations exhibited greater potency after 72 hrs in comparison to earlier time points. GAP-107B8 was found to be a peptide-based inhibitor of protein kinase B (Akt) with a strong potential for anti-cancer properties.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2907. doi:1538-7445.AM2012-2907

A selectable and excisable marker system for the rapid creation of recombinant poxviruses

BACKGROUND

Genetic manipulation of poxvirus genomes through attenuation, or insertion of therapeutic genes has led to a number of vector candidates for the treatment of a variety of human diseases. The development of recombinant poxviruses often involves the genomic insertion of a selectable marker for purification and selection purposes. The use of marker genes however inevitably results in a vector that contains unwanted genetic information of no therapeutic value.

METHODOLOGY/PRINCIPAL FINDINGS

Here we describe an improved strategy that allows for the creation of marker-free recombinant poxviruses of any species. The Selectable and Excisable Marker (SEM) system incorporates a unique fusion marker gene for the efficient selection of poxvirus recombinants and the Cre/loxP system to facilitate the subsequent removal of the marker. We have defined and characterized this new methodological tool by insertion of a foreign gene into vaccinia virus, with the subsequent removal of the selectable marker. We then analyzed the importance of loxP orientation during Cre recombination, and show that the SEM system can be used to introduce site-specific deletions or inversions into the viral genome. Finally, we demonstrate that the SEM strategy is amenable to other poxviruses, as demonstrated here with the creation of an ectromelia virus recombinant lacking the EVM002 gene.

CONCLUSION/SIGNIFICANCE

The system described here thus provides a faster, simpler and more efficient means to create clinic-ready recombinant poxviruses for therapeutic gene therapy applications.

Abstract 2592: Therapeutic testing of a novel inhibitor GAP-107B8 on ovarian cancer cells

Background: Ovarian cancer is the most fatal gynaecologic disease in the western world. In 2010 in the United States, an estimated 21,880 women will develop ovarian cancer and an estimated 13,850 women will succumb to this disease. Current treatments are limited to surgery and chemotherapy, but the disease often recurs highlighting the need for novel cancer therapeutics. We are currently evaluating the efficacy of a novel therapeutic, GAP-107B8 (PharmaGap Inc, Ottawa) using in vitro and in vivo models. GAP-107B8 was designed as a protein kinase C (PKC) inhibitor. The PKC family of serine/threonine kinases are involved in cellular proliferation, differentiation, apoptosis and cell polarity. One PKC isoform, PKC iota, has recently been identified as a human oncogene and has been shown to be overexpressed in epithelial ovarian cancers and is thus a potential therapeutic target for ovarian cancer. Objectives: 1) To test the novel inhibitor GAP-107B8 on ovarian cancer cell lines to determine its effects on cell proliferation, cell cycle progression and apoptosis; and 2) To determine the therapeutic potential of GAP-107B8 in xenograft models of two different ovarian cancer cell lines. Methods: Three ovarian cancer cell lines were treated with three different concentrations of GAP-107B8 and screened using high throughput assays to measure the proliferation of cells in adherent cultures. Apoptosis was measured by TUNEL staining, PARP cleavage and cell cycle analysis. Tumor burden was assessed in mice receiving subcutaneous implants of two ovarian cancer cell lines, followed by daily intra-tumoral injections of GAP-107B8. Results: GAP-107B8 caused a significant reduction in cell proliferation in 3 ovarian cancer cell lines tested (86% to 95%; p<0.001), including a cell line resistant to standard chemotherapy. In vivo, intra-tumoral treatment with GAP-107B8 resulted in a 45% reduction in average tumor size in the A2780cp-derived tumours (n=6/group, p<0.01) and 75% in the HEY-derived tumors (n=3/group, p<0.001). Cell killing may be mediated by apoptosis based on the observation of TUNEL staining 30 hours after treatment of cells in vitro with GAP-107B8. Apoptosis was confirmed by flow cytometry and PARP cleavage. GAP-107B8 also inhibited progression of cells through the cell cycle by blocking or delaying progression of cells through G2/M into the G1 phase.

Conclusion: The novel inhibitor GAP-107B8 displays good efficacy in vitro in suppressing the proliferation of ovarian cancer cell lines. Cytotoxicity may be manifested in perturbations of the cell cyle and induction of apoptosis. Finally, GAP-107B8 showed therapeutic efficacy in ovarian cancer xenograft models.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2592. doi:10.1158/1538-7445.AM2011-2592

Abstract 2536: Therapeutic testing of a novel PKC inhibitor GAP-107B8 on ovarian cancer cells

Background: Ovarian cancer is the most fatal gynaecologic disease in the western world. In 2009 in North America, an estimated 23,896 women will develop ovarian cancer and an estimated 15,24050 women will die from this disease. Current treatments are limited to surgery or chemotherapy, but the disease often recurs. Thus, the development of novel cancer therapeutics remains important. The protein kinase C (PKC) family of serine/threonine kinases is involved in cellular proliferation, differentiation, apoptosis and cell polarity. One PKC isoform, PKC iota, has recently been identified as a human oncogene and has been shown to be overexpressed in serous epithelial ovarian cancers and is thus a potential therapeutic target for ovarian cancer. Objective: We have tested a novel PKC inhibitor GAP-107B8 (PharmaGap Inc., Ottawa) in vitro on a panel of nine ovarian cancer cell lines to determine its potential to inhibit cell proliferation, proliferation in soft agar, and migration. Methods: Nine ovarian cancer cell lines were treated with three different concentrations of GAP-107B8 and then screened using high throughput assays to measure the proliferation of cells in adherent and anchorage independent (soft agar) cultures. The ability of cells to migrate in the presence of GAP-107B8 was also determined. Results: We observed significant reduction in cell proliferation in 6 of 9 ovarian cancer cell lines tested, including two cell lines resistant to the standard chemotherapy. GAP-107B8 inhibited cell proliferation by 30% to 79% compared with untreated cells, with more than 50% inhibition in 4 of 7 cell lines. Treatment with GAP-107B caused a reduction in growth in soft agar in 7 of the 9 cell lines tested in vitro. GAP-107B8 inhibited growth in soft agar by 50% to 94% compared with untreated cells, with 80% or greater inhibition in 6 of 7 cell lines. Finally, 5 of 8 cell lines tested showed significant inhibition of mobility following treatment with GAP-107B8. There was 50% or greater inhibition in all 5 cell lines compared with untreated cells. Conclusion: The novel PKC inhibitor GAP-107B8 displays good efficacy in vitro in suppressing several cancer cell characteristics in a variety of ovarian cancer cell lines. Further experiments are underway to investigate the therapeutic potential of GAP-107B8 in xenograft models of ovarian cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2536.

17beta-estradiol accelerates tumor onset and decreases survival in a transgenic mouse model of ovarian cancer

Epithelial ovarian cancer is thought to be derived from the ovarian surface epithelium (OSE) but often goes undetected in the early stages, and as a result, the factors that contribute to its initiation and progression remain poorly understood. Epidemiological studies have suggested that the female steroid hormones are involved in ovarian carcinogenesis and that women who use hormone replacement therapy are at increased risk of developing the disease. A novel transgenic mouse model of ovarian cancer (tgCAG-LS-TAg) was developed to examine the role of the female reproductive steroid hormones [17beta-estradiol (E(2)) and progesterone (P(4))] on the initiation, progression, and pathology of ovarian cancer. The mouse model uses the Cre-LoxP system to induce expression of the simian virus 40 large and small T antigens (SV40 TAg). After targeted induction of the oncogene in the OSE, mice develop poorly differentiated ovarian tumors, tumor dissemination to tissues within the abdominal cavity, and a subset develops hemorrhagic ascites. Treatment with P(4) had no impact on the disease, but E(2) altered the pathophysiology, resulting in an earlier onset of tumors, decreased overall survival time, and a distinctive papillary histology. Normal ovaries collected from mice treated with E(2), but lacking expression of SV40 TAg, displayed an increase in the areas of columnar and hyperplastic OSE cells compared to placebo-treated controls. A better understanding of the mechanisms by which E(2) alters the morphology of normal OSE cells and reduces survival in this mouse model may translate into improved prevention and treatment options for women using hormone replacement therapy.

Susceptibility of ascites tumor cells to ex-vivo killing by the oncolytic virus JX-963 in epithelial ovarian cancer

e16537

Background: Epithelial ovarian cancer (EOC) has a poor prognosis, and novel therapies are urgently needed. One-third of patients with EOC will develop clinical ascites, an adverse prognostic factor. The ascitic fluid is rich in tumor cells which can be purified and used as a valuable source of patient material for in vitro analysis. In this study, we describe a method to evaluate the efficacy of ascitic tumor cell killing by the oncolytic virus, JX-963 (vaccinia strain) currently approved for use in a NCIC-CTG phase I trial. Methods: Research ethics approval and patient consent was obtained for this study. 15 samples were collected prospectively with relevant clinicopathologic information. Infection with JX-963 was performed using viral doses ranging from a multiplicity of infection (MOI) of 0.5 to 8. Following a seven-day infection period, viability was assessed using the Alamar Blue metabolic assay and tracked by virally encoded green fluorescent protein (eGFP) expression, immunohistochemistry (IHC) and flow cytometry. Results: A standardized protocol was developed for the collection and purification of EOC cells from patient ascites for subsequent infection and quantification of viral killing. Qualitative analysis using phase contrast imaging of the total cell content showed greater opaque dead cell aggregates with increasing MOI over time. Although variable between individual samples, there was a strong correlation between escalating MOI and enhanced cell death in all patient ascites samples, when quantified by Alamar Blue assay and confirmed by flow cytometry and IHC. Similar cell killing profiles by JX-963 were observed for ascites tumor cells derived from both chemotherapy-naïve patients and chemotherapy-exposed (>1 prior line of chemotherapy) patients. Conclusions: EOC cells from patient ascites show effective but differential susceptibility to viral oncolysis by the JX-963 virus that appears to be independent of prior exposure to chemotherapy. The relevance of this work is that in an individual patient, this assay will allow the testing of panels of oncolytic viruses to identify candidate viral therapeutics which may predict response to treatment.

No significant financial relationships to disclose.

[The mouse ovarian surface epithelium cells (MOSE) transformation induced by c-myc/K-ras in]

OBJECTIVE

To study the function of c-myc and K-ras in tumorigenesis of ovarian cancer.

METHODS

K-ras and/or c-myc cDNAs were introduced into mouse ovarian surface epithelium cells (MOSE) using recombinant Moloney retroviral vectors. The resulting MOSE cells were studied by cell proliferation assays, the ability to form colonies in soft agarose, matrigel invasion assays and tumorigenicity assays in nude mice.

RESULTS

K-ras and c-myc can be easily delivered to the normal MOSE cells by recombinant retroviruses. mRNA and protein of the target genes can be detected by RT-PCR and Western blot. Cell proliferation assays showed that MOSE-Ras cells and MOSE-RM cells (MOSE-Ras/Myc) grew more rapidly than parental cells (MOSE) and MOSE-Myc cells (P <0.01). In addtition, MOSE-RM cells grew more rapidly than MOSE-Ras cells (P <0. 05). Cell colony formation assays showed that while MOSE-Ras and MOSE-RM cells can form colonies in soft-agarose, the MOSE-Myc and MOSE cells did not. Matrigel invasion assays showed that MOSE-Ras and MOSE-RM cells have invasion ability, but not MOSE-Myc ascites and the control MOSE cells. Xenograft experiments showed that MOSE-Ras and MOSE-RM cells were able to form tumors in nude mice following intraperitoneal injection. Tumors were not observed in animals injected with either MOSE-Myc or MOSE cells.

CONCLUSION

The recombinant Moloney retroviral system is a highly efficient and convenient method for introducing and expressing foreign genes in murine surface epithelial cell cultures. In this model, expression of K-ras alone is sufficient to generate tumorigenic MOSE, however expression of c-myc in conjunction with K-ras results in cells with a higher index of malignancy. Based on the assays described in this report, expression of c-myc alone can not transform MOSE cultures although it does play a role in cooperation with K-ras.

Conditional inactivation of Brca1 in the mouse ovarian surface epithelium results in an increase in preneoplastic changes

Epithelial ovarian cancer (EOC) is thought to arise from the ovarian surface epithelium (OSE); however, the molecular events underlying this transformation are poorly understood. Germline mutations in the BRCA1 tumor suppressor gene result in a significantly increased risk of developing EOC and a large proportion of sporadic EOCs display some sort of BRCA1 dysfunction. Using mice with conditional expression of Brca1, we inactivated Brca1 in the murine OSE and demonstrate that this inactivation results in the development of preneoplastic changes, such as hyperplasia, epithelial invaginations, and inclusion cysts, which arise earlier and are more numerous than in control ovaries. These changes resemble the premalignant lesions that have been reported in human prophylactic oophorectomy specimens from women with BRCA1 germline mutation. We also report that inactivation of Brca1 in primary cultures of murine OSE cells leads to a suppression of proliferation due to increased apoptosis that can be rescued by concomitant inactivation of p53. These observations, along with our finding that these cells display an increased sensitivity to the DNA-damaging agent cisplatin, indicate that loss of function of Brca1 in OSE cells impacts both cellular growth control and DNA-damage repair which results in altered cell behavior manifested as morphological changes in vivo that arise earlier and are more numerous than what can be attributed to ageing.

[*OPCML gene transferred by recombinant lentiviruses in vitro and its inhibition to ovarian cancer cells]

OBJECTIVE

To study the inhibition of OPCML on ovarian cancer cell lines using a lentiviral vector system for efficient gene transduction.

METHODS

The murine OPCML cDNA was amplified by PCR from CD1 murine brain cDNA using gene specific primers, and subcloned into the lentiviral vector, pWPI-GFP, to generate the lentiviral expression vector, pWPI-OPCML. Recombinant lentiviruses were produced by 293T cells following the co-transfection of pWPI-OPCML, with the packaging plasmids pCMV-dR8.74 and pMDG. The resulting recombinant lentiviruses which carried OPCML or control viruses (only carrying GFP), were then used to infect the human ovarian cancer cell lines A2780 and OCC1 in addition to normal CD1 mouse ovarian surface epithelial cells. The infected cells were then characterized by cell proliferation assays, cell aggregation assays, cell cycle analysis by flow cytometry and tumorigenicity assays following injection into nude mice.

RESULTS

(1) The efficiency of infection of the cell lines using the lentiviral vectors was almost 100% allowing the stable expression of OPCML in nearly all cells. Stable expression of OPCML (60 000) and GFP (27 000) proteins was confirmed by western blot analysis. (2) A2780 cells expressing OPCML [(7.6 +/- 1.0) x 10(5)] grew slowly compared to A2780 parental [(20.0 +/- 2.6) x 10(5)] or control virus infected cells [(18.1 +/- 1.7) x 10(5), P < 0.01], but the expression of OPCML had no effect on the proliferation rates of OCC1 and the normal CD1 cells when compared to their respective parental or controls (P > 0.05). (3) Flow cytometry based cell cycle assays showed that the expression of OPCML could arrest A2780 cells (G(0) approximately G(1) 67% vs 75%, P < 0.05); but not OCC1, CD1 cells. (4) The rate of aggregation of single cell suspensions was measured and found to be increased in all cell lines expressing OPCML indicating the increased cell surface adhesion mediated by OPCML. (5) A2780 cells expressing OPCML only formed a single tumor in 1/4 mice (10 mg) which was significantly smaller than controls [4/4; A2780 (280 +/- 53) mg and A2780/pWPI (677 +/- 323) mg; P < 0.01]. Expression of OPCML in tumor was confirmed by immunohistochemistry.

CONCLUSIONS

The use of lentiviral vectors allowed the efficient expression of OPCML in nearly 100% of target cells. Expression of the OPCML cDNA resulted in an increase of cell adhesion in all cell lines tested, and decreased the proliferation and tumorigenicity of the A2780 ovarian cancer cell line. This indicates that the OPCML may be a new tumor suppressor gene.

Models of ovarian cancer--are we there yet?

Ovarian cancer is the most lethal of all gynecological cancers and arises most commonly from the surface epithelium. Successful clinical management of patients with epithelial ovarian cancer is limited by the lack of a reliable and specific method for early detection, and the frequent recurrence of chemoresistant disease. Experimental models are of crucial importance not only to understand the biological and genetic factors that influence the phenotypic characteristics of the disease but also to utilize as a basis for developing rational intervention strategies. Ovarian cancer cell lines derived from ascites or primary ovarian tumors have been used extensively and can be very effective for studying the processes controlling growth regulation and chemosensitivity or evaluating novel therapeutics, both in vitro and in xenograft models. While our limited knowledge of the initiating events of ovarian cancer has restricted the development of models in which the early pathogenic events can be studied, recent advances in the ability to manipulate gene expression in ovarian surface epithelial cells in vitro and in vivo have begun to provide insights into the molecular changes that may contribute to the development of ovarian cancer. This review highlights the strengths and weaknesses of some of the current models of ovarian cancer, with special consideration of the recent progress in modeling ovarian cancer using genetically engineered mice.

Translational research in ovarian cancer: a must

Ovarian cancer discovered at late clinical stage continues to be a fatal disease. It seems self-evident that if we are to make an impact on the survival of advanced ovarian cancer patients, we must begin to understand the disease more completely. This should improve the diagnosis of the disease at an early stage when it is curable by surgery or develop better/targeted drug treatments. Modern molecular techniques have provided insights into many of the molecular changes that occur when ovarian cancer develops, but one must understand that changes seen in this way can only be said to correlate with disease. It would be helpful to have a way to test candidate changes for causality. In many cancer types, genetically engineered animals are beginning to be used for this purpose and as a means to study the disease process in greater detail. To date, there has been no way to study ovarian cancer by this means. Efforts to model human ovarian cancer have been delayed by a general lack of understanding both of the disease process in humans and of the cells widely believed to be the precursors of epithelial ovarian cancer, the ovarian surface epithelial (OSE) cells. Here, we present recent progress in modeling ovarian cancer using genetically modified mice.

Generation of tumors in transgenic mice expressing the SV40 T antigen under the control of ovarian-specific promoter 1

OBJECTIVE

The ovarian-specific promoter, OSP-1, which was cloned from the transcript of a rat retrovirus-like element specifically expressed in ovarian tissue, was tested for its ability to drive ovary-specific transcription in transgenic mice.

METHODS

Transgenic mice were generated with the lacZ reporter gene (OSP-lacZ) or the early region of SV40 virus (OSP-TAg) placed under the control of the OSP-1 promoter. OSP-lacZ and OSP-TAg transgenic animals were examined, respectively, for the expression of lacZ (OSP-lacZ) or the development of tumors (OSP-TAg).

RESULTS

The expression of lacZ in the resulting OSP-lacZ mice was restricted to the ovary as determined by X-gal staining of multiple organs. Immunohistochemical detection of beta-galactosidase showed lacZ expression mainly in the granulosa cells and ovarian surface epithelial cells. OSP-TAg mice developed tumors in a variety of tissues, including unilateral granulosa cell tumors in two of three female founder mice. In the contralateral ovary of one mouse with a granulosa cell tumor, there were alterations in the ovarian surface epithelial cells suggestive of preneoplasia.

CONCLUSIONS

Although the OSP-1 promoter was able to restrict reporter gene expression to the ovary in transgenic mice, the expression of TAg in the OSP-TAg mice resulted in ovarian tumors as well as tumors in numerous other organs. This indicated that although transcription from the OSP-1 promoter occurs predominantly in the ovary, this promoter is sufficiently leaky in cells in other tissues to permit their tumorigenic conversion by SV40 TAg.

Translational research in ovarian cancer: a must

Ovarian cancer discovered at late clinical stage continues to be a fatal disease. It seems self-evident that if we are to make an impact on the survival of advanced ovarian cancer patients, we must begin to understand the disease more completely. This should improve the diagnosis of the disease at an early stage when it is curable by surgery or develop better/targeted drug treatments. Modern molecular techniques have provided insights into many of the molecular changes that occur when ovarian cancer develops, but one must understand that changes seen in this way can only be said to correlate with disease. It would be helpful to have a way to test candidate changes for causality. In many cancer types, genetically engineered animals are beginning to be used for this purpose and as a means to study the disease process in greater detail. To date, there has been no way to study ovarian cancer by this means. Efforts to model human ovarian cancer have been delayed by a general lack of understanding both of the disease process in humans and of the cells widely believed to be the precursors of epithelial ovarian cancer, the ovarian surface epithelial (OSE) cells. Here, we present recent progress in modeling ovarian cancer using genetically modified mice.

Cell-cell interaction modulates myoD-induced skeletal myogenesis of pluripotent P19 cells in vitro

P19 embryonal carcinoma cells can be induced to differentiate in culture to develop into a wide variety of cell types that include skeletal muscle. Skeletal myogenesis is controlled by transcription factors of the bHLH class, such as myoD. Expression of myoD from transfected genes did not induce significant amounts of myogenesis in P19 cells and it was possible to establish lines of undifferentiated P19[myoD] cells that express high levels of myoD mRNA. These P19[myoD] cells remained undifferentiated when cultured on solid surfaces but when allowed to aggregate, P19[myoD] cells differentiated efficiently into skeletal muscle. Aggregation did not increase the amount of myoD mRNA or the amount of myoD protein in P19[myoD] cells. The myoD protein was present in the nucleus in cells grown as attached or aggregated cultures and, in both culture conditions, the myoD protein was associated with transcription factors of the E2A family and was able to bind DNA at E-box sequences. Thus, the aggregation-induced myogenesis of P19[myoD] cells occurs in the absence of change in the myoD protein, suggesting that the cell-cell contact achieved in aggregates may result in the induction of an activity that increases accessibility of the myoD transcription factor to muscle-specific genes in chromatin.

Surf5: a gene in the tightly clustered mouse surfeit locus is highly conserved and transcribed divergently from the rpL7A (Surf3) gene

The four previously characterized genes (Surf1 to 4) of the mouse Surfeit locus do not share any sequence homology, and the transcription of each gene alternates with respect to its neighbor(s). Adjacent Surfeit genes are separated by very small distances, and two of the genes overlap at their 3' ends. In this work we have further defined the Surfeit gene cluster by the isolation of Surf5, a fifth gene of the locus, and determination of its relationship to the other Surfeit genes. Surft5 does not share any sequence homology with the four cloned Surfeit genes. The transcription of Surf5 is divergent with respect to its neighbor the Surf3 gene, and the 5' ends of Surf5 and Surf3 are separated by only 159 bp, suggesting the presence of a second bidirectional promoter in the locus. The 3' end of Surf5 maps only 68 bp away from the processed 3' end of a pseudogene. The human and partial chicken Surf5 coding regions show greater than 95% identity, and a Caenorhabditis elegans homologue shows 38% identity and 56% similarity with the mouse Surf5 amino acid sequence. The 3.5-kb transcript of Surf5 encodes a small hydrophilic protein of 140 amino acid residues, which differs from the ribosomal protein L7a encoded by the Surf3 gene or the integral membrane protein encoded by the Surf4 gene. Subcellular fractionation located the Surf5 protein to the soluble fraction of the cytoplasm. The surfeit locus appears to represent a novel type of gene cluster in which the genes are unrelated by sequence or function; however, their organization may play a role in their gene expression.

The organization and conservation of the human Surfeit gene cluster and its localization telomeric to the c-abl and can proto-oncogenes at chromosome band 9q34.1

The mouse Surfeit locus contains an unusually tight cluster of six housekeeping genes (Surf-1 to -6) which are unrelated by sequence homology. Using a mouse Surfeit locus probe, a 16 kb clone has been isolated which contains the human Surf-1 and Surf-3 genes and regions of the human Surf-2 and Surf-5 genes. The organization and juxtaposition of these human Surfeit locus genes are the same as found in the mouse. Using the human clone as a biotinylated probe for fluorescence in situ hybridization (FISH) we have confirmed the location of the human Surfeit locus to chromosome band 9q34. Metaphase spreads of human chronic myeloid leukemic cells containing the t(9;22)(q34;q11) translocation involving The c-abl gene at 9q34.1 an acute nonlymphocytic leukemic cells containing the t(6;9)(q34;p23) translocation involving the can gene at 9q34.1 were analyzed by FISH using the human Surfeit clone as a probe. These analyses locate the human Surfeit locus telomeric to the c-abl and can genes at chromosome band 9q34.1.

Conservation of the organization of five tightly clustered genes over 600 million years of divergent evolution

The organization of the mouse surfeit locus is unusual in that it contains six housekeeping genes (Surf-1-Surf-6), which are unrelated by sequence homology, in the tightest mammalian gene cluster thus far described. A maximum of only 73 base pairs separates any two of the four well-characterized genes, and two of the genes overlap at their 3' ends. The direction of transcription of each of the five surfeit genes, Surf-1-Surf-5, alternates with respect to that of its neighbor, suggesting cis-interaction or coregulation between the genes by mechanisms such as the sharing of regulatory elements and/or antisense regulation. The Surf-3 gene has been identified as encoding the ribosomal protein L7a (Rpl7a). We have used the high conservation of the Rpl7a gene to clone the chicken gene and surrounding genomic DNA. The tight clustering and juxtaposition of at least five of the surfeit genes (Surf-1-Surf-5) and their associated CpG-rich islands have been found to be conserved over the 600 million years of divergent evolution that separates birds and mammals. This strongly suggests that the surfeit locus represents a different form of gene cluster in which gene organization may play both a positive and negative regulatory role in gene expression possibly via cis-interactions between the closely spaced genes.

Mapping of the functional domains of the v-rel oncogene

Previously, the v-rel oncogene was shown to code for a protein of 503 amino acids. The protein product of v-rel was identified as a 59 kDa protein (pp59v-rel), phosphorylated predominantly on serine residues. Although the signal required for the nuclear localization of pp59v-rel in chicken embryo fibroblasts was identified, the regions of v-rel important for transformation have not been mapped. In this study, 12 linker insertion mutants of v-rel were constructed and tested for transforming activity. Seven linker insertion mutants which mapped between amino acid residues 29 and 275 abolished transformation. The remaining 5 mutants which contained linker insertion mutations between amino acid residues 332 and 459 transformed at wild type levels. The results of this analysis localize the functional domains of the v-rel oncogene to the N-terminus. Earlier reports have shown that pp59v-rel resides in a high molecular weight complex with several other cellular proteins. The transforming mutants co-precipitated the same set of cellular proteins when immunoprecipitated with v-rel antiserum. This indicates that all transforming mutants retained the ability to bind within the reported complex.

The N-terminal env-derived amino acids of v-rel are required for full transforming activity

Expression of the v-rel oncogene of the reticuloendotheliosis virus, strain T (REV-T), can mediate the transformation of chicken spleen and bone marrow cells. Although the majority of the coding sequence of the v-rel oncogene is derived from the cellular rel sequence, the N- and C-terminal amino acids are coded for by remnants of the REV env gene. The resulting v-rel protein can be described as an env-rel-(out of frame env) fusion protein. Terminal deletion mutants were constructed to determine the role that env sequences play in the transforming activity of v-rel. Deletions were designed to remove only sequences of v-rel derived from former env sequence. Additional deletions removed more substantial amounts of coding sequence. Introduction of deleted genes into an REV-T based retroviral vector permitted the transforming activities to be determined. Deletion analysis indicated that the N-terminal region of pp59v-rel is required for the transforming activity, whereas as many as 100 C-terminal amino acids could be deleted without complete loss of the activity.

Identification of the v-rel protein in REV-T transformed chicken bone marrow cells and expression in Cos1 cells

The product of the v-rel oncogene has been identified as a 55,000 dalton protein using antiserum prepared against a synthetic polypeptide whose sequence was deduced from the DNA sequence of v-rel. This antiserum was used in a Western blot assay to identify the product of v-rel in chicken bone marrow cells transformed with reticuloendotheliosis virus, strain T (REV-T), and in Cos1 cells transfected with an expression vector containing the v-rel gene. Transient expression of v-rel under the transcriptional control of the SV40 late promoter in Cos1 cells leads to the synthesis of a rel specific protein with a similar molecular weight.

Isolation of intact polysomes from mechanically dehulled developing grain

A rapid method for obtaining large quantities of developing groats suitable for the isolation of highly intact polysomes has been developed. Developing spikelets were harvested directly from oat panicles into liquid nitrogen and then quickly passed through a dehuller. Chaff was removed by air aspiration and the resultant groats were collected directly back into liquid nitrogen. Approximately 250 g of groats could be isolated each man-hour by the above method. In comparison, only 10 g of endosperm could be collected by squeezing it out of spikelets using an endosperm mangle. Membrane-bound polysomes extracted from the immature groats were compared to those extracted from endosperm. The largest polysomes discernable as unique peaks on sucrose gradients were ten-mers and nine-mers for groats and endosperm, respectively. Polysomes isolated from both starting materials stimulated similar incorporations of [35S]methionine into trichloroacetic acid-insoluble products during in vitro translations in wheat germ extract. Both polysome preparations directed the synthesis of similar high-molecular-weight proteins. Based on these criteria, polysomes from both preparations were found to be of similar intactness, although the groat starting material was much more readily obtained. The polysome classes having the maximum absorbance peak for endosperm and groat polysomes were six-mers and eight-mers, respectively.