Therapeutic Target For Ovarian Cancer Research Articles

The SP1-12LOX axis promotes chemoresistance and metastasis of ovarian cancer

BackgroundOvarian cancer is the most lethal gynecologic cancer. Chemoresistance, especially platinum-resistance, is closely related to metastasis of ovarian cancer, however, the molecular basis by which links chemoresistance and metastasis remains vague. Disordered arachidonic acid (AA) metabolism has been shown to play an important role in the advanced ovarian cancer. This study aimed to explore the underlying mechanism involving eicosanoid metabolism that controlling chemoresistance and metastasis of ovarian cancer.MethodsCisplatin (DDP)-resistant SKOV3 (SKOV3-R) cells were constantly induced. Ultra-high-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) was performed to determine the AA metabolism in SKOV3 and SKOV3-R cells. Half maximal inhibitory concentration (IC50) and percentage of cell viability were tested using cell counting kit 8 (CCK-8). Realtime quantitative PCR (qPCR) and immunohistochemistry (IHC) were used to evaluate indicated genes and proteins respectively. Bioinformatic analysis and chromatin immunoprecipitation (ChIP) were performed to predict and identify the co-transcription factor of interest genes. Tumor growth and metastasis in the liver were assessed with nude mice by subcutaneously injection of SKOV3-R cells.ResultsSKOV3-R cells expressed higher multidrug resistance-associated proteins (MRPs) MRP1 and MRP4. They showed enhanced metastatic ability and produced increased AA-derived eicosanoids. Mechanistically, MRPs, epithelial mesenchymal transition (EMT) markers Snail and Slug, as well as key enzymes involved in AA-metabolism including 12-lipoxygenase (12LOX) were transcribed by the mutual transcription factor SP1 which was consistently upregulated in SKOV3-R cells. Inhibition of SP1 or 12LOX sensitized SKOV3-R cells to DDP and impaired metastasis in vitro and in vivo.ConclusionOur results reveal that SP1-12LOX axis signaling plays a key role in DDP-resistance and metastasis, which provide a new therapeutic target for ovarian cancer.

HVEM/HIF-1\u03b1 promoted proliferation and inhibited apoptosis of ovarian cancer cells under hypoxic microenvironment conditions

BackgroundOur previous studies showed the expression of herpes virus entry mediator (HVEM) is high in ovarian cancer samples and correlated to the patient clinic pathological features. As we all know, the hypoxic environment is the main feature of tumor. In this work, we explored the role of HVEM in hypoxic ovarian cancer cells and its effects on HIF-1α, a transcription factor responding to hypoxia.MethodsThe expression of HVEM, HIF-1α and apoptosis-related genes was detected by qRT-PCR and western blot. The proliferation and apoptosis of the ovarian cancer cells were determined with the Cell Counting Kit-8 assay and AnnexinV-FITC/PI-stained flow cytometry assay, respectively.ResultsThe expression of HVEM was positively correlated to that of HIF-1α. The expression of HVEM and HIF-1α under hypoxic conditions was higher than that under normoxic conditions, which suggested that the level of HVEM and HIF-1α correlates with prolonged periods of hypoxia in ovarian cancer. The overexpression of HVEM promoted cell proliferation and inhibited cell apoptosis under hypoxic condition. HVEM overexpression elevated the expression of HIF-1α and Bcl-2 (anti-apoptotic protein), and reduced the expression of Bax (pro-apoptotic protein). In addition, overexpression of HVEM activated the AKT/mTOR signaling. Moreover, knockdown of HVEM had the completely opposite effects.ConclusionThese data indicated that HVEM signaling might promote HIF-1α activity via AKT/mTOR signaling pathway and thus to regulate tumor growth in ovarian cancer under the hypoxic conditions. Furthermore, these findings indicate that this molecular mechanism could represent a therapeutic target for ovarian cancer.

Nicotinamide N-methyltransferase overexpression may be associated with poor prognosis in ovarian cancer

Ovarian cancer is the fifth leading cause of cancer-related mortality in women. Nicotinamide N-methyltransferase (NNMT) is a metabolic enzyme and there is growing evidence to suggest that it plays an important role in cancer progression. This is the first study to examine the expression of NNMT in serous ovarian cystadenomas, serous borderline tumours, low grade serous carcinomas (LGSC) and high grade serous carcinomas (HGSC) and investigate the potential independent association of NNMT expression with survival. Tissue samples were analysed immunohistochemically for NNMT expression. The stromal NNMT score was significantly higher in HGSC compared to serous cystadenomas and serous borderline tumours (p < .001, p < .043, respectively). The mean stromal NNMT score of patients with HGSC was significantly higher than patients with LGSC (p = .043). Patients with low expression of NNMT had a significantly higher mean recurrence-free survival than patients with high expression (p = .036). NNMT may support tumour progression in ovarian cancer by promoting desmoplastic stromal tumour reaction. NNMT overexpression may be associated with poor prognosis and can be a therapeutic target in ovarian cancer. IMPACT STATEMENT What is already known on this subject? Nicotinamide N-methyltransferase (NNMT) is a cytosolic enzyme that is overexpressed in many malignancies. Its overexpression was shown to lead to histone hypomethylation, which in turn can decrease and increase the expression of tumour suppressor proteins and onco-proteins, respectively. NNMT was also shown to play a role in epithelial-to-mesenchymal transition, which is critical in tumour progression and the stromal tumour reaction. The stromal tumour reaction was recently targeted with promising therapeutic results in ovarian cancer. What do the results of this study add? The expression of NNMT in various ovarian neoplasms including serous cystadenomas, borderline tumours and serous carcinomas has not been studied and independently associated with poor survival, previously. This study suggests that NNMT is progressively overexpressed in the stroma of ovarian neoplasms from benign cysts to HGSCs. NNMT overexpression appears to be independently associated with poor survival in ovarian cancer. What are the implications of these findings for clinical practice and/or further research? The implications of these findings are that NNMT may play an important role in the stromal tumour reaction, and therefore its overexpression may contribute to poor survival. NNMT overexpression may be an important target of ovarian cancer therapy.

Role of RGS10 in the ovarian cancer microenvironment

Ovarian cancer is the deadliest of gynecological cancers and is associated with a high rate of chemoresistance. The discovery of more effective treatments and new therapeutic targets in ovarian cancer requires disease models that better represent the tumor microenvironment and account for dynamic crosstalk between multiple cell types. Macrophages, one of the most abundant immune cells in the tumor microenvironment, are actively recruited into the tumor and can accelerate tumor progression and chemoresistance via the production of inflammatory mediators. Recently, our lab and others have established Regulator of G protein Signaling 10 as a key regulator of inflammatory signaling in both macrophages and ovarian cancer cells. RGS10 robustly regulates macrophage activation and polarization by suppressing the production of inflammatory cytokines TNF‐α and IL‐6. Further, RGS10 suppresses the activation of cyclooxygenase‐2 (COX2) expression in both ovarian cancer cells and macrophages. However, the regulatory role of RGS10 in the tumor microenvironment where macrophages and ovarian cancer cells have direct interaction has not been explored, and it is not known if RGS10 regulatory roles in these distinct cell types will be synergistic or oppositional. Further, RGS10’s role in cancer progression has not been investigated in an in vivo tumor xenograft model with an intact macrophage population. The current study employs both an in vitro co‐culture model of macrophages and ovarian cancer cell lines and an in vivo syngeneic ovarian tumor model using mouse ID8 ovarian cancer cells to define the role of RGS10 in inflammatory signaling between immune and tumor cells in the ovarian cancer microenvironment.Support or Funding InformationMarsha Rivkin Foundation, University of Georgia

Circ-PGAM1 promotes malignant progression of epithelial ovarian cancer through regulation of the miR-542-3p/CDC5L/PEAK1 pathway.

BackgroundEpithelial ovarian cancer (EOC) is the most common ovarian malignant cancer. Circular RNA is a type of endogenous noncoding RNA and is considered as a novel regulatory molecule in the development and progression of tumors. This study investigated the expression and functions of a circular RNA, circular‐phosphoglycerate mutase 1 (circ‐PGAM1), in EOC tissues and cells.MethodsThe expression of circ‐PGAM1 and miR‐542‐3p in EOC was analyzed using quantitative RT‐PCR. Immunohistochemistry and western blot were performed to confirm the localization and expression of cell division cycle 5‐like (CDC5L) and pseudopodium enriched atypical kinase 1 (PEAK1) in EOC tissues. Cell lines (CAOV3 and OVCAR3) overexpressing or silencingcirc‐PGAM1 and miR‐542‐3p were established to explore the functions of circ‐PGAM1 and miR‐542‐3p in ovarian cancer cells. Furthermore, dual‐luciferase reporter assay was performed to study the interactions between circ‐PGAM1 and miR‐542‐3p and between miR‐542‐3p and CDC5L. CCK‐8, transwell, and flow cytometry were used to study the effect of circ‐PGAM1 and miR‐542‐3p on cell biological behaviors including proliferation, migration, invasion, and apoptosis. The interaction between CDC5L and the PEAK1 gene promoter was confirmed using chromatin immunoprecipitation (ChIP).ResultsCirc‐PGAM1 was upregulated in EOC tissues, whereas linear PGAM1 was not deregulated in EOC tissues. Silencing of circ‐PAGM1 inhibited proliferation, migration, and invasion of ovarian cancer cells and promoted cell apoptosis. MiR‐542‐3p was downregulated in EOC tissues, and miR‐542‐3p overexpression inhibited malignant progression of ovarian cancer cells. Circ‐PGAM1 directly interacted with miR‐542‐3p, with mutual negative feedback between them. CDC5L was a direct target of miR‐542‐3p and played an oncogenic role in ovarian cancer cells. Furthermore, the CDC5L protein binds directly to the PEAK1 promoter to promote its transcription. PEAK1 overexpression activated ERK1/2 and JAK2 signaling pathways and promoted malignant biological behaviors of ovarian cancer cells. Circ‐PAGM1 silencing combined with miR‐542‐3p overexpression played the greatest anticancer role in vivo.ConclusionThe circ‐PGAM1/miR‐542‐3p/CDC5L/PEAK1 pathway played an important role in the progression of ovarian cancer and might be a novel therapeutic target for ovarian cancer.

LncRNA MIF-AS1 aggravates the progression of ovarian cancer by sponging miRNA-31-5p.

The aim of this study was to uncover the role of lncRNA MIF-AS1 in influencing the biological phenotypes of ovarian cancer (OC) and the underlying mechanism. OC tissues and adjacent normal tissues were collected from 50 OC patients. The expression level of lncRNA MIF-AS1 in OC tissues and cells was determined by quantitative Real-Time Polymerase Chain Reaction (qRT-PCR). The prognostic potential of MIF-AS1 in OC patients was assessed by the Kaplan-Meier method. Subsequently, the regulatory effects of MIF-AS1 on proliferative, migratory, and invasive abilities of ES-2 and HO-8910 cells were evaluated by a series of functional experiments. Dual-Luciferase reporter gene assay, qRT-PCR, and Western blot were further conducted to verify the interaction in the regulatory loop MIF-AS1/miRNA-31-5p/PLCB1. MIF-AS1 was significantly upregulated in OC tissues and cell lines (p<0.05). Higher level of MIF-AS1 predicted significantly worse prognosis of OC patients (p<0.05). The knockdown of MIF-AS1 markedly attenuated the proliferative, migratory, and invasive abilities of ES-2 and HO-8910 cells (p<0.05). Dual-Luciferase reporter gene assay verified that MIF-AS1 competed with PLCB1 to bind miRNA-31-5p. In addition, MIF-AS1 negatively regulated miRNA-31-5p expression cells, and miRNA-31-5p negatively regulated PLCB1 expression in OC. MIF-AS1 was significantly upregulated in OC, which accelerated the proliferative, migratory, and invasive abilities of OC cells. Furthermore, the regulatory loop MIF-AS1/miRNA-31-5p/PLCB1 could be utilized as a therapeutic target for OC.

Upregulated CXCL14 is associated with poor survival outcomes and promotes ovarian cancer cells proliferation.

Ovarian cancer is one of the common malignant tumours of female reproductive organs. Due to early diagnosis difficulties and lack of effective treatment in the late stage, ovarian cancer has the highest mortality rate in female reproductive system malignancies. Therefore, finding reliable early diagnosis indicators and new therapeutic targets for ovarian cancer is an urgent problem to be solved. Chemokine (C-X-C motif) ligand 14 (CXCL14) is a small cytokine belonging to the CXC chemokine family, which has been found to possess multi-effects in tumourigenesis and development. Here, we reported that CXCL14 was preferentially expressed in ovarian cancer. By analysing the TCGA database, we found that CXCL14 was highly expressed in advanced ovarian cancer patients and correlated with poor prognosis. In addition, the abnormal high CXCL14 levels were observed in serum and ovarian tissue of ovarian cancer patients by qRT-PCR and ELISA. In vitro and in vivo experiments both confirmed that overexpression of CXCL14 promoted the ovarian cancer cell proliferation. Moreover, transfection of CXCL14 increased the phosphorylation level of signal transducer and activator of transcription 3 (STAT3), and administration of STAT3 inhibitor III inhibited the tumour-promoting effects of CXCL14. Therefore, our study suggests that CXCL14 could be utilised as a novel adjunct biomarker for early diagnosis of ovarian cancer and provides new targets and ideas for the treatment of advanced ovarian cancer. SIGNIFICANCE PARAGRAPH: CXCL14 could be utilised as a novel adjunct biomarker for early diagnosis of ovarian cancer and provides new targets and ideas for the treatment of advanced ovarian cancer.

Knockdown of enhancer of rudimentary homolog inhibits proliferation and metastasis in ovarian cancer by regulating epithelial-mesenchymal transition

Ovarian cancer (OC) is the deadliest gynecological malignancy. The pathogenesis of molecular in epithelial ovarian cancer (EOC), main histological type of OC, has not been completely defined. Enhancer of rudimentary homolog (ERH) had been reported to participate in transcriptional regulation, mRNA splicing, DNA repair and DNA synthesis by binding a variety of proteins. In this study, immunohistochemical staining revealed that the protein expression of ERH was associated with histological type, lymph node metastasis and pathological grade in EOC patients. To verify the association of ERH with the prognosis of OC, a GSE microarray dataset was downloaded from the Gene Expression Omnibus (GEO) database. Survival analysis suggested that ERH may be associated with poor prognosis of OC. In addition, shRNA was used to knockdown the protein and mRNA expression levels of ERH in the OC cell line SKOV3. Inhibition of ERH expression slowed proliferation, promoted apoptosis and inhibited metastasis and invasion by regulating epithelial-mesenchymal transition (EMT) in SKOV3 cells. These results indicate that ERH protein promotes the development of OC and provides an experimental basis for ERH as the potential target for ovarian cancer treatment.

Divergent metabolic responses dictate vulnerability to NAMPT inhibition in ovarian cancer.

It is of current interest to target cancer metabolism as treatment for many malignancies, including ovarian cancer (OVC), in which few druggable driver mutations have been identified. Nicotinamide phosphoribosyltransferase (NAMPT), a rate-limiting enzyme in the NAD salvage pathway, is a potential therapeutic target in OVC. However, factors that determine responsiveness to NAMPT inhibition are not fully understood. Here, we report that OVC cell lines can be divided into subgroups exhibiting NAMPT-dependent or NAMPT-independent glycolysis, and these metabolic differences correlate with vulnerability to NAMPT inhibition. Interestingly, cells showing NAMPT-dependent glycolysis were enriched in a group of cells lacking BRCA1/2 gene mutations. Our findings suggest the importance of selecting appropriate patients for NAMPT-targeting therapy in OVC.

PLAG1 silencing promotes cell chemosensitivity in ovarian cancer via the IGF2 signaling pathway.

Ovarian cancer (OC) is one of the most lethal gynecological diseases. Novel prognostic biomarkers and therapeutic targets for OC are urgently required. The aim of this study was to investigate the mechanisms that govern how pleomorphic adenoma gene 1 (PLAG1) influences the biological processes and chemosensitivity of OC cells via the insulin-like growth factor-2 (IGF2) signaling pathway. Differentially expressed genes in OC were selected based on bioinformatics data. OC and adjacent tissue specimen were collected, followed by the determination of the expression of PLAG1 and IGF2 signaling pathway-associated genes. The regulatory mechanisms of PLAG1 in OC cells were analyzed following treatment with pcDNA or small interfering RNA (siRNA), and included the assessment of cell proliferation, migration, invasion and cisplatin resistance. PLAG1 was identified as an upregulated gene in OC. OC tissues exhibited increased expression of PLAG1 and IGF2 compared with the controls. Moreover, PLAG1 was observed to positively regulate the IGF2 signaling pathway. The siRNA-mediated silencing of PLAG1 resulted in decreased expression of IGF2, IGF1 receptor and insulin receptor substrate 1, as well as inhibited proliferation, migration, invasion and cisplatin resistance of OC cells. Furthermore, the effect of PLAG1 was dependent on IGF2. PLAG1 may therefore be considered as a possible target for the treatment of OC.

Circular RNAs and their emerging roles as diagnostic and prognostic biomarkers in ovarian cancer.

Ovarian cancer (OC), one of the gynecologic malignancies with high invasive and metastatic potential, has a low survival rate in females. Although cytoreductive surgery combined with chemotherapy is the principal treatment for OC, the prognosis remains poor, and the recurrence rate of OC remains high. It is urgent to explore novel biomarkers for the diagnosis and prognosis of OC, as well as therapeutic targets. Circular RNAs (circRNAs) are a class of highly conserved, stable and abundant noncoding RNAs (ncRNAs). Recent studies have shown that circRNAs participate in OC progression by regulating various processes, including cell proliferation, migration, invasion and apoptosis. In addition, circRNAs are potential biomarkers for OC diagnosis and prognosis. This review provides an overview of recent findings on circRNAs in OC, including their functions and molecular mechanisms, and discusses their potential roles as diagnostic and prognostic biomarkers, as well as therapeutic targets for OC.

Immunoblotting Analysis of Intracellular PD-L1 Levels in Interferon-γ-Treated Ovarian Cancer Cells Stably Transfected with Bcl3 shRNA.

Expression of the immune checkpoint programmed death ligand 1 (PD-L1, CD274) is increased in many types of cancer, including ovarian cancer (OC), but the mechanisms that regulate the PD-L1 expression are not fully understood. In addition to binding to PD-1 on T cells, thus inhibiting T cell-mediated antitumor responses, PD-L1 has also tumor-intrinsic effects that include increased cancer cell survival and proliferation, and that might be in part mediated by the intracellular PD-L1. In this chapter, we describe a protocol for the analysis of the intracellular PD-L1 protein levels in OC cells by immunoblotting. Our results show that interferon-γ (IFNγ) induces the intracellular levels of PD-L1 and the proto-oncogene Bcl3 in OC cells. However, the PD-L1 expression is significantly decreased in OC cells stably transfected with Bcl3 shRNA, demonstrating that the IFNγ-induced PD-L1 expression in OC cells is mediated by Bcl3. These data identify the IFNγ-Bcl3-PD-L1 axis as a novel therapeutic target in OC, and suggest that targeting Bcl3 may provide a novel strategy to regulate the PD-L1 expression, and especially the tumor-intrinsic PD-L1 effects mediated by the intracellular PD-L1 in OC cells.

High expression of maternal embryonic leucine-zipper kinase (MELK) impacts clinical outcomes in patients with ovarian cancer and its inhibition suppresses ovarian cancer cells growth ex vivo.

ObjectiveMaternal embryonic leucine zipper kinase (MELK) is receiving an attention as a therapeutic target in various types of cancers. In this study, we aimed to evaluate the prognostic significance of MELK expression in ovarian cancer using clinical samples, and assessed the efficacy of a small molecule MELK inhibitor, OTS167, using patient-derived ovarian cancer cells as well as cell lines.MethodsExpression levels of MELK in 11 ovarian cancer cell lines were confirmed by western blotting. Inhibitory concentration of OTS167 was determined by colorimetric assay. MELK messenger RNA (mRNA) expression was evaluated in 228 ovarian cancer patients by quantitative polymerase chain reaction. Growth inhibition of OTS167 was also evaluated using freshly-isolated primary ovarian cancer cells including spheroid formation condition.ResultsMELK mRNA expression was significantly higher in ovarian cancer than in normal ovaries (p<0.001), and high MELK mRNA expression was observed in patients with advanced stage, positive ascites cytology and residual tumor size. Patients with high MELK mRNA expression showed shorter progression-free survival (p=0.001). Expression of MELK was also confirmed in 10 of 11 ovarian cancer cell lines tested, and the half maximal inhibitory concentration of MELK inhibitor, OTS167, ranged from 9.3 to 60 nM. Additionally, OTS167 showed significant growth inhibitory effect against patient-derived ovarian cancer cells, regardless of their tumor locations, histologic subtypes and stages.ConclusionsWe demonstrated MELK as both a prognostic marker and a therapeutic target for ovarian cancer using clinical ovarian cancer samples. MELK inhibition by OTS167 may be an effective approach to treat ovarian cancer patients.

CADM1 inhibits ovarian cancer cell proliferation and migration by potentially regulating the PI3K/Akt/mTOR pathway

Previous studies have shown that cell adhesion molecule 1 (CADM1), an immunoglobulin superfamily member, is frequently inactivated but functions as a tumor suppressor in many solid tumors. However, the characterization of CADM1 expression in ovarian cancer cells and the mechanisms of its tumor suppressor function are not fully understood. We generated ovarian cancer cell lines in which CADM1 was stably upregulated or downregulated. CADM1 expression was significantly decreased in ovarian cancer tissue and cells lines. Functionally, knockdown of CADM1 promoted the growth, migration and invasion of ovarian cancer cells. Conversely, further experimental evidence indicated that overexpression of CADM1 inhibited the migration and invasion of ovarian cancer cells potentially through inhibition of the PI3K/Akt/mTOR signaling pathway by regulating upstream regulators (LXR/RXR, IGF1, IFI44L and C4BPA) and downstream effectors (APP, EDN1, TGFBI and Rap1A). In conclusion, CADM1 inhibits ovarian cancer cell proliferation and migration by potentially regulating the PI3K/Akt/mTOR signaling pathway. CADM1 could be a potential therapeutic target for ovarian cancer.

KRCC1: A potential therapeutic target in ovarian cancer

Using a systems biology approach to prioritize potential points of intervention in ovarian cancer, we identified the lysine rich coiled-coil 1 (KRCC1), as a potential target. High-grade serous ovarian cancer patient tumors and cells express significantly higher levels of KRCC1 which correlates with poor overall survival and chemoresistance. We demonstrate that KRCC1 is predominantly present in the chromatin-bound nuclear fraction, interacts with HDAC1, HDAC2, and with the serine-threonine phosphatase PP1CC. Silencing KRCC1 inhibits cellular plasticity, invasive properties, and potentiates apoptosis resulting in reduced tumor growth. These phenotypes are associated with increased acetylation of histones and with increased phosphorylation of H2AX and CHK1, suggesting the modulation of transcription and DNA damage that may be mediated by the action of HDAC and PP1CC, respectively. Hence, we address an urgent need to develop new targets in cancer.

Abstract GMM-035: TARGETING SPSB1 SENSITIZES PLATINUM-RESISTANT OVARIAN CANCER CELLS TO CISPLATIN

Abstract OBJECTIVE: Emergence of chemoresistance remains a critical clinical issue responsible for treatment failure in patients with ovarian cancer. The precise mechanisms underlying the development of chemoresistance are not fully understood. In our previous study using methylomic and transcriptomic analyses, SPRY domain-containing SOCS box protein 1 (SPSB1) was found to be differentially expressed between cisplatin-sensitive and –resistant ovarian cancer cells. Here, we investigated the roles of SPSB1 as a new therapeutic target for ovarian cancer cells resistant to cisplatin. METHODS: Knockdown of SPSB1 gene was performed by transfection of SPSB1 siRNA. Ovarian cancer cell lines were cultured for 5 days and 12 days after transfection for MTT assay and colony forming assay, respectively. Protein level was analyzed by western blot analysis. Cell migration assay was performed using Boyden chamber method. RESULTS: Knockdown of SPSB1 using RNAi method dramatically inhibited cell viability and migratory capability of ovarian cancer cells. Also, SPSB1 knockdown significantly induced CDK inhibitors, p21 and p27 and inhibited anti-apoptotic Bcl-2, indicating that SPSB1 inhibition induces cell cycle arrest and apoptosis in ovarian cancer cells. CONCLUSION: Our results suggest that SPSB1 might be a potential therapeutic target for cisplatin-resistant ovarian cancer. Citation Format: Mi-Kyung Kim, Hyun-Jung Kim, Yun Hwan Kim, Seung Cheol Kim, Woong Ju. TARGETING SPSB1 SENSITIZES PLATINUM-RESISTANT OVARIAN CANCER CELLS TO CISPLATIN [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr GMM-035.

Abstract GMM-018: CD73: A NEW DRIVER AND A THERAPEUTIC TARGET IN OVARIAN CANCER STEM CELLS

Abstract Many biological and clinical features of ovarian cancer (OC) support the notion that the disease is driven by a subpopulation of self-renewing cancer stem cells (CSC) that are able to generate the entire progeny of short-lived, differentiated and heterogeneous cells that compose the tumor bulk. Ovarian cancer stem cells (OCSC), in particular, have been proposed to drive and sustain tumor dissemination, recurrence and chemoresistance, most likely due to their slow cycling rate and their detoxifying molecular machineries. This provides the rationale for investigating OCSC as suitable targets for OC eradication. Our study aims at assessing the functional contribution of OCSC to OC etiology and progression and at defining their molecular and functional traits. Specifically, we are pursuing these objectives through the accomplishment of the following milestones: 1) collection of normal and pathological samples; 2) identification of OCSC based on functional properties; 3) molecular profiling of OCSC and their normal counterpart; 4) characterization of novel genes/pathways involved in OCSC function (clonogenicity, tumorigenicity, quiescence, chemoresistance, etc.). We have established a repository of patient-derived primary cells isolated either from OC or from its tissues of origin, ovarian surface or fallopian tube epithelium. The OCSC subpopulation and their normal counterpart were then derived from primary cultures and used to profile their specific transcriptome, inferring a OCSC signature. Among the genes differentially expressed in OCSC, we focused on CD73, which encodes a membrane-associated 5'-ectonucleotidase that accounts for the generation of extracellular adenosine. Genetic ablation experiments revealed that CD73 acts as a driver of OC cell stemness and tumor initiation. Furthermore, the pharmacological inhibition of CD73 reduced OCSC self-renewal and tumorigenesis, highlighting the druggability of CD73 in the context of OCSC-directed therapies. The biological function of CD73 in OCSC required its enzymatic activity and involved adenosine signaling. Mechanistically, CD73 promotes the expression of stemness and epithelial-mesenchymal transition-associated genes, implying a regulation of OCSC function at the transcriptional level. In summary, CD73 is involved in OCSC biology and may represent a therapeutic target for innovative treatments aimed at OC eradication. In this context, CD73 is involved in tumor immune escape and actively investigated as a target to restore antitumor response. Thus, CD73-targeted therapies may combine the benefit of OCSC neutralization with overcoming CD73-driven immune escape, resulting in a synergistic effect towards OC eradication. Furthermore, CD73 neutralization might help preventing OCSC-dependent chemoresistance, thus enhancing the therapeutic efficacy of conventional chemotherapy. The therapeutic potential of CD73-based treatments and the molecular function of CD73 in OCSC are currently under investigation. Citation Format: Michela Lupia, Kris F. Sachsenmeier, Nicoletta Colombo, Fabrizio Bianchi, and Ugo Cavallaro. CD73: A NEW DRIVER AND A THERAPEUTIC TARGET IN OVARIAN CANCER STEM CELLS [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr GMM-018.

P28GANK overexpression is associated with chemotherapy resistance and poor prognosis in ovarian cancer.

The non-ATPase regulatory subunit 10 of the human 26S proteasome (p28GANK) has been implicated in the tumorigenesis and progression of several types of malignant tumor. The aim of the present study was to detect the expression of p28GANK in ovarian cancer (OC) and investigate its association with the clinicopathological features and prognosis of OC. The expression levels of p28GANK were determined in 114 OC tissue samples and 30 normal ovarian tissue samples using immunohistochemistry. An association was observed between p28GANK overexpression and certain clinicopathological factors, including advanced International Federation of Gynecology and Obstetrics stage (P=0.042), residual tumor size (P=0.005) and response to chemotherapy (P<0.001). Furthermore, patients with high expression of p28GANK demonstrated worse overall survival (OS) and disease-free survival (DFS) rates compared with patients with low expression of p28GANK (both P<0.001). Multivariate Cox regression analysis revealed that overexpression of p28GANK was an independent prognostic factor of OS and DFS in patients with OC (P=0.013 and P=0.001, respectively). In summary, the current results indicate that p28GANK may be a predictive marker and a therapeutic target for OC.

Ubiquitin-specific peptidase 39 regulates the process of proliferation and migration of human ovarian cancer via p53/p21 pathway and EMT.

Ovarian cancer is one of the most lethal gynecological cancers; owning to its late detection and chemoresistance, understanding the pathogenesis of this malignant tumor is much critical. Previous studies have reported that ubiquitin-specific peptidase 39 (USP39) is generally overexpressed in a variety of cancers, including hepatocellular carcinoma, gastric cancer and so forth. Furthermore, USP39 is proved to be associated with the proliferation of malignant tumors. However, the function and mechanism of USP39 in ovarian cancer have not been elucidated. In the present study, we observed that USP39 was frequently overexpressed in human ovarian cancer and was highly correlated with TNM stage. Suppression of USP39 markedly inhibited the growth and migration of ovarian cancer cell lines HO-8910 and SKOV3 and induced cell cycle G2/M arrest. Moreover, knockdown of USP39 inhibited ovarian tumor growth in a xenograft model. In addition, our findings indicated that cell cycle arrest induced by USP39 knockdown might be involved in p53/p21 signaling pathway. Furthermore, we found that the depletion of USP39 inhibited the migration of ovarian cancer cells via blocking epithelial-mesenchymal transition. Taken together, these results suggest that USP39 may play vital roles in the genesis and progression and may serve as a potential biomarker for diagnosis and therapeutic target of ovarian cancer.

RETRACTED: Downregulation of Rab23 inhibits proliferation, invasion, and metastasis of human ovarian cancer

Previously, we reported that the expression of human epididymis protein (HE4) was correlated with the expression of RAB23 in ovarian cancer cells. Rab23 is a member of the Ras-related small GTPase superfamily, which plays a key role in the Sonic Hedgehog (Shh) signaling pathway. However, the function of Rab23 in ovarian cancer remains unclear. In this study, we explored the location and expression of Rab23 in ovarian cancer tissues and cells (CaoV3 and A2780), and further investigated the function and potential mechanism of Rab23 in malignant biological behaviors including the epithelial-mesenchymal transition (EMT) process in ovarian cancer for the first time. Rab23 is highly expressed in ovarian cancer tissues and associated with advanced stage, and shortened overall survival time of ovarian cancer patients. We are the first to report that human epididymis protein (HE4) can regulate the expression of the Rab23 protein, and that knockdown of RAB23 decreases the proliferation, invasion, and migration abilities as well as inhibits the epithelial-mesenchymal transition (EMT) process in ovarian cancer cells. Furthermore, downregulation of Rab23 significantly inhibited Shh-Gli1 and PI3K-AKT signaling pathways. Collectively, our results indicate that Rab23 plays a critical role in the malignant biological behavior of ovarian cancer and may serve as a potential biomarker and therapeutic target for ovarian cancer.