Survival Of Ovarian Cancer Cells Research Articles

Claudin-4 stabilizes the genome via nuclear and cell cycle remodeling to support ovarian cancer cell survival.

Alterations in the interplay between the nucleus and the cell cycle during cancer development lead to a state of genomic instability, often accompanied by observable morphological aberrations. Tumor cells can regulate these aberrations to evade cell death, either by preventing or eliminating genomic instability. In epithelial ovarian cancer (EOC), overexpression of claudin-4 significantly contributes to therapy resistance through mechanisms associated with genomic instability regulation. However, the molecular mechanisms underlying claudin-4 overexpression in EOC remain poorly understood. In this study, we modified claudin-4 expression and employed a unique claudin mimic peptide (CMP) to investigate claudin-4's function. Our findings show that claudin-4 supports ovarian cancer cell survival by stabilizing the genome through nuclear and cell cycle remodeling. Specifically, claudin-4 induced nuclear constriction by excluding lamin B1 and promoting perinuclear F-actin accumulation, thereby altering nuclear structure and dynamics. Similarly, cell cycle modifications due to claudin-4 overexpression resulted in fewer cells entering the S-phase and reduced genomic instability in tumors. Importantly, disrupting claudin-4's biological effects using CMP and forskolin increased the efficacy of PARP inhibitor treatment, correlating with alterations in the oxidative stress response. Our data indicate that claudin-4 protects tumor genome integrity by modulating the crosstalk between the nucleus and the cell cycle, leading to resistance to genomic instability formation and the effects of genomic instability-inducing agents.

A novel ITGB8 transcript variant sustains ovarian cancer cell survival through genomic instability and altered ploidy on a mutant p53 background

BackgroundTranscript variants and protein isoforms are central to unique tissue functions and maintenance of homeostasis, in addition to being associated with aberrant states such as cancer, where their crosstalk with the mutated tumor suppressor p53 may contribute to genomic instability and chromosomal rearrangements. We previously identified several novel splice variants in ovarian cancer RNA-sequencing datasets; herein, we aimed to elucidate the biological effects of the Integrin Subunit Beta 8 variant (termed pITGB8-205).MethodsResolution of the full-length sequence of pITGB8-205 through rapid amplification of cDNA ends (RACE-PCR). Cell cycle analysis and karyotype studies were performed to further explore genomic instability. RNA-seq and proteomics analyses were used to identify the differential expression of the genes.ResultsThis full-length study revealed a unique 5’ sequence in pITGB8-205 that differed from the reported ITGB8-205 sequence, suggesting differential regulation of this novel transcript. Under a p53 mutant background, overexpression of pITGB8-205 triggered genetic instability reminiscent of oncogene-induced replicative stress with extensive abnormal mitoses and chromosomal and nuclear aberrations indicative of chromosomal instability, leading to near whole-genome duplication that imposes energy stress on cellular resources. Micronuclei and aneuploidy are striking features of pITGB8-205-overexpressing p53-mutant cells but are not enhanced in p53 wild-type (WT) cells. RNA-seq and proteomics analyses further suggested that p53 inactivation in ovarian cancer provides a permissive intracellular molecular niche for pITGB8-205 to mediate its effects on genomic instability. This observation is pivotal considering that most high-grade serous ovarian carcinoma (HGSC) tumors express mutant p53. The resulting aneuploid clones with enhanced self-renewal and survival capabilities disrupt clonal dominance under stress yet maintain a balance between replicative stress and prosurvival advantages.ConclusionpITGB8-205-overexpressing clones sustain ovarian tumor cell survival, achieve homeostasis and are formidable opponents of therapy.

Carcinoma-associated mesenchymal stem cells promote ovarian cancer heterogeneity and metastasis through mitochondrial transfer

Ovarian cancer is characterized by early metastatic spread. This study demonstrates that carcinoma-associated mesenchymal stromal cells (CA-MSCs) enhance metastasis by increasing tumor cell heterogeneity through mitochondrial donation. CA-MSC mitochondrial donation preferentially occurs in ovarian cancer cells with low levels of mitochondria ("mito poor"). CA-MSC mitochondrial donation rescues the phenotype of mito poor cells, restoring their proliferative capacity, resistance to chemotherapy, and cellular respiration. Receipt of CA-MSC-derived mitochondria induces tumor cell transcriptional changes leading to the secretion of ANGPTL3, which enhances the proliferation of tumor cells without CA-MSC mitochondria, thus amplifying the impact of mitochondrial transfer. Donated CA-MSC mitochondrial DNA persisted in recipient tumor cells for at least 14days. CA-MSC mitochondrial donation occurs invivo, enhancing tumor cell heterogeneity and decreasing mouse survival. Collectively, this work identifies CA-MSC mitochondrial transfer as a critical mediator of ovarian cancer cell survival, heterogeneity, and metastasis and presents a unique therapeutic target in ovarian cancer.

Netrin signaling mediates survival of dormant epithelial ovarian cancer cells.

Dormancy in cancer is a clinical state in which residual disease remains undetectable for a prolonged duration. At a cellular level, rare cancer cells cease proliferation and survive chemotherapy and disseminate disease. We created a suspension culture model of high-grade serous ovarian cancer (HGSOC) dormancy and devised a novel CRISPR screening approach to identify survival genes in this context. In combination with RNA-seq, we discovered the Netrin signaling pathway as critical to dormant HGSOC cell survival. We demonstrate that Netrin-1, -3, and its receptors are essential for low level ERK activation to promote survival, and that Netrin activation of ERK is unable to induce proliferation. Deletion of all UNC5 family receptors blocks Netrin signaling in HGSOC cells and compromises viability during the dormancy step of dissemination in xenograft assays. Furthermore, we demonstrate that Netrin-1 and -3 overexpression in HGSOC correlates with poor outcome. Specifically, our experiments reveal that Netrin overexpression elevates cell survival in dormant culture conditions and contributes to greater spread of disease in a xenograft model of abdominal dissemination. This study highlights Netrin signaling as a key mediator HGSOC cancer cell dormancy and metastasis.

Crizotinib Enhances PARP Inhibitor Efficacy in Ovarian Cancer Cells and Xenograft Models by Inducing Autophagy.

Poly (ADP-ribose) polymerase inhibitors (PARPi) can encounter resistance through various mechanisms, limiting their effectiveness. Our recent research showed that PARPi alone can induce drug resistance by promoting autophagy. Moreover, our studies have revealed that anaplastic lymphoma kinase (ALK) plays a role in regulating the survival of ovarian cancer cells undergoing autophagy. Here, we explored whether the ALK-inhibitor crizotinib could enhance the efficacy of PARPi by targeting drug-induced autophagic ovarian cancer cell and xenograft models. Our investigation demonstrates that crizotinib enhances the anti-tumor activity of PARPi across multiple ovarian cancer cells. Combination therapy with crizotinib and olaparib reduced cell viability and clonogenic growth in two-olaparib resistant cell lines. More importantly, this effect was consistently observed in patient-derived organoids. Furthermore, combined treatment with crizotinib and olaparib led to tumor regression in human ovarian xenograft models. Mechanistically, the combination resulted in increased levels of reactive oxygen species (ROS), induced DNA damage, and decreased the phosphorylation of AKT, mTOR, and ULK-1, contributing to increased olaparib-induced autophagy and apoptosis. Notably, pharmacologic, or genetic inhibition or autophagy reduced the sensitivity of ovarian cancer cell lines to olaparib and crizotinib treatment, underscoring the role of autophagy in cell death. Blocking ROS mitigated olaparib/crizotinib-induced autophagy and cell death while restoring levels of phosphorylated AKT, mTOR and ULK-1. These findings suggest that crizotinib can improve the therapeutic efficacy of olaparib by enhancing autophagy. Implications: The combination of crizotinib and PARPi presents a promising strategy, that could provide a novel approach to enhance outcomes for patients with ovarian cancer.

Dual‑regulated oncolytic adenovirus carrying ERCC1‑siRNA gene possesses potent antitumor effect on ovarian cancer cells.

Ovarian cancer is a multifactorial and deadly disease. Despite significant advancements in ovarian cancer therapy, its incidence is on the rise and the molecular mechanisms underlying ovarian cancer invasiveness, metastasis and drug resistance remain largely elusive, resulting in poor prognosis. Oncolytic viruses armed with therapeutic transgenes of interest offer an attractive alternative to chemical drugs, which often face innate and acquired drug resistance. The present study constructed a novel oncolytic adenovirus carrying ERCC1 short interfering (si)RNA, regulated by hTERT and HIF promoters, termed Ad‑siERCC1. The findings demonstrated that this oncolytic adenovirus effectively inhibits the proliferation, migration and invasion of ovarian cancer cells. Furthermore, the downregulation of ERCC1 expression by siRNA ameliorates drug resistance to cisplatin (DDP) chemotherapy. It was found that Ad‑siERCC1 blocks the cell cycle in the G1 phase and enhances apoptosis through the PI3K/AKT‑caspase‑3 signaling pathways in SKOV3 cells. The results of the present study highlighted the critical effect of oncolytic virus Ad‑siERCC1 in inhibiting the survival of ovarian cancer cells and increasing chemotherapy sensitivity to DDP. These findings underscore the potent antitumor effect of Ad‑siERCC1 on ovarian cancers in vivo.

Deletion of PTP4A3 phosphatase in high grade serous ovarian cancer cells decreases tumorigenicity and produces marked changes in intracellular signaling pathways and cytokine release.

The oncogenic protein tyrosine phosphatase PTP4A3 is frequently overexpressed in human ovarian cancers and is associated with poor patient prognosis. PTP4A3 is thought to regulate multiple oncogenic signaling pathways, including STAT3, SRC, and ERK. The objective of this study was to generate ovarian cancer cells with genetically depleted PTP4A3; to assess their tumorigenicity; to examine their cellular phenotype; and to uncover changes in their intracellular signaling pathways and cytokine release profiles. Genetic deletion of PTP4A3 using CRISPR/Cas9 enabled the generation of individual clones derived from single cells isolated from the polyclonal knockout population. We observed a >90% depletion of PTP4A3 protein levels by Western blotting in the clonal cell lines compared to the sham transfected wildtype population. The wildtype and polyclonal knockout cell lines shared similar monolayer growth rates, while the isolated clonal populations 2B4, 3C9, and 3C12 exhibited significantly lower monolayer growth characteristics consistent with their lower PTP4A3 levels. The clonal PTP4A3 knockout cell lines also had substantially lower in vitro colony formation efficiencies compared to the wildtype cells and were less tumorigenic in vivo The clonal knockout cells were markedly less responsive to IL-6-stimulated migration in a scratch wound assay compared to the wildtype cells. Antibody microarray assays documented differences in cytokine release and intracellular phosphorylation patterns in the PTP4A3 deleted clones. Bioinformatic network analyses indicated alterations in cellular signaling nodes. These biochemical changes could ultimately form the foundation for pharmacodynamic endpoints useful for emerging anti-PTP4A3 therapeutics. Significance Statement Clones of high grade serous ovarian cancer cells were isolated in which the oncogenic phosphatase PTP4A3 was deleted using CRISPR/Cas9 methodologies. The PTP4A3 null cells exhibited loss of in vitro proliferation, colony formation, and migration, and reduced in vivo tumorigenesis. Marked differences in intracellular protein phosphorylation and cytokine release were seen. The newly developed PTP4A3 knockout cells should provide useful tools to probe the role of PTP4A3 phosphatase in ovarian cancer cell survival, tumorigenicity and cell signaling.

Abstract A028: Investigating the role of SOX2 in promoting anchorage-independent survival of ovarian cancer cells

Abstract Ovarian cancer (OVCA) is the most lethal gynecologic malignancy, often detected at an advanced stage. OVCA progression involves transcoelomic metastasis, where tumor cells disseminate into the peritoneal ascites. Malignant cells in the ascites adapt to survive under Anchorage-Independent (A-I) conditions by altering the expression of genes escalating anoikis (A-I cell death) resistance and metastasis. Our lab has shown that OVCA cells manipulate their transcriptomic profile to promote the expression of anoikis resistance genes in A-I. Expression profiling of genes upregulated in A-I revealed the transcription factor SRY-Box Transcription Factor 2 (SOX2) to be highly upregulated in response to OVCA cell detachment. While we have previously demonstrated that SOX2 is necessary for the A-I survival of OVCA cells, the specific mechanism underlying SOX2-dependent A-I survival remains unknown. RNA-sequencing studies performed in the high-grade serous ovarian cancer cell line, OVCAR3, revealed that the Leucine-rich repeat-containing G-protein coupled receptor 5, LGR5, is the most significantly upregulated gene in A-I compared to attached conditions. Importantly, amongst those genes that are upregulated in A-I, LGR5 is significantly downregulated following SOX2 knockdown in A-I. LGR5 is an ‘orphan’ G-protein coupled receptor known to modulate canonical Wnt signaling upon interacting with its ligand R-spondin1 (RSPO1). Time-course experiments in OVCAR3 cells revealed a striking increase in LGR5 expression that peaked after 24 hours in A-I. Furthermore, siRNA mediated knockdown of SOX2 downregulated LGR5 expression only in A-I, suggesting that LGR5 is a potential SOX2 target under A-I conditions. Interestingly, bioinformatics analysis of the existing OVCA datasets from the Cancer Genome Atlas showed increased expression of RSPO1, which correlated with a significant decrease in the overall survival of OVCA patients. Interaction of LGR5 with its ligand RSPO1 is crucial for the receptor to signal through the Wnt pathway to promote cell survival and cancer stemness. Although SOX2 and LGR5 are established markers of cancer stemness in various tumor types, their direct relationship in promoting tumor progression and regulation of OVCA A-I cell survival remains unknown. Our data suggests that increased SOX2 and LGR5 expression could drive OVCA cell survival under A-I conditions. Our current studies focus on understanding the molecular mechanisms behind SOX2-driven regulation of LGR5 and the role of LGR5 in driving OVCA A-I cell survival. Citation Format: Shriya Kamlapurkar, Coryn Stump, Mythreye Karthikeyan, Nadine Hempel. Investigating the role of SOX2 in promoting anchorage-independent survival of ovarian cancer cells [abstract]. In: Proceedings of the AACR Special Conference on Ovarian Cancer; 2023 Oct 5-7; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(5 Suppl_2):Abstract nr A028.

Engineered CAR-Tcells targeting the non-functional P2X purinoceptor 7 (P2X7) receptor as a novel treatment for ovarian cancer.

Recent studies have identified expression of the non-functional P2X7 (nfP2X7) receptor on various malignant cells including ovarian cancer, but not on normal cells, which makes it a promising tumour-associated antigen candidate for chimeric antigen receptor (CAR)-T-cell immunotherapies. In this study, we assessed the cytotoxic effects of nfP2X7-CAR-T cells on ovarian cancer using in vitro and in vivo models. We evaluated the effects of nfP2X7-CAR-T cells on ovarian cancer cell lines (SKOV-3, OVCAR3, OVCAR5), normal peritoneal cells (LP-9) and primary serous ovarian cancer cells derived from patient ascites invitro using monolayer and 3D spheroid assays. We also evaluated the effects of nfP2X7-CAR-T cells on patient-derived tissue explants, which recapitulate an intact tumour microenvironment. In addition, we investigated the effect of nfP2X7-CAR-T cells in vivo using the OVCAR-3 xenograft model in NOD-scid IL2Rγnull (NSG) mice. Our study found that nfP2X7-CAR-T cells were cytotoxic and significantly inhibited survival of OVCAR3, OVCAR5 and primary serous ovarian cancer cells compared with un-transduced CD3+ Tcells in vitro. However, no significant effects of nfP2X7-CAR-T cells were observed for SKOV3 or normal peritoneal cells (LP-9) cells with low P2X7 receptor expression. Treatment with nfP2X7-CAR-T cells increased apoptosis compared with un-transduced Tcells in patient-derived explants and correlated with CD3 positivity.Treatment with nfP2X7-CAR-T cells significantly reduced OVCAR3 tumour burden in mice compared with un-transduced CD3 cells for 7-8 weeks. This study demonstrates that nfP2X7-CAR-T cells have great potential to be developed as a novel immunotherapy for ovarian cancer.

Unveiling the Significance of FGF8 Overexpression in Orchestrating the Progression of Ovarian Cancer.

The asymptomatic nature, high rate of disease recurrence, and resistance to platinum-based chemotherapy highlight the need to identify and characterize novel target molecules for ovarian cancer. Fibroblast growth factor 8 (FGF8) aids in the development and metastasis of ovarian cancer; however, its definite role is not clear. We employed ELISA and IHC to examine the expression of FGF8 in the saliva and tissue samples of epithelial ovarian cancer (EOC) patients and controls. Furthermore, various cell assays were conducted to determine how FGF8 silencing influences ovarian cancer cell survival, adhesion, migration, and invasion to learn more about the functions of FGF8. In saliva samples, from controls through low-grade to high-grade EOC, a stepped overexpression of FGF8 was observed. Similar expression trends were seen in tissue samples, both at protein and mRNA levels. FGF8 gene silencing in SKOV3 cells adversely affected various cell properties essential for cancer cell survival and metastasis. A substantial reduction was observed in the cell survival, cell adhesion to the extracellular matrix, migration, and adhesion properties of SKOV3 cells, suggesting that FGF8 plays a crucial role in the development of EOC. Conclusively, this study suggests a pro-metastatic function of FGF8 in EOC.

Disruption of Ovarian Cancer STAT3 and p38 Signaling with a Small-Molecule Inhibitor of PTP4A3 Phosphatase.

Protein tyrosine phosphatase type IVA member 3 (PTP4A3 or PRL-3) is a nonreceptor, oncogenic, dual-specificity phosphatase that is highly expressed in many human tumors, including ovarian cancer, and is associated with a poor patient prognosis. Recent studies suggest that PTP4A3 directly dephosphorylates SHP-2 phosphatase as part of a STAT3-PTP4A3 feedforward loop and directly dephosphorylates p38 kinase. The goal of the current study was to examine the effect of a PTP4A phosphatase inhibitor, 7-imino-2-phenylthieno[3,2-c]pyridine-4,6(5H,7H)-dione (JMS-053), on ovarian cancer STAT3, SHP-2, and p38 kinase phosphorylation. JMS-053 caused a concentration- and time-dependent decrease in the activated form of STAT3, Y705 phospho-STAT3, in ovarian cancer cells treated in vitro. In contrast, the phosphorylation status of two previously described direct PTP4A3 substrates, SHP-2 phosphatase and p38 kinase, were rapidly increased with JMS-053 treatment. We generated A2780 and OVCAR4 ovarian cancer cells resistant to JMS-053, and the resulting cells were not crossresistant to paclitaxel, cisplatin, or teniposide. JMS-053-resistant A2780 and OVCAR4 cells exhibited a 95% and 50% decrease in basal Y705 phospho-STAT3, respectively. JMS-053-resistant OVCAR4 cells had an attenuated phosphorylation and migratory response to acute exposure to JMS-053. These results support a regulatory role for PTP4A phosphatase in ovarian cancer cell STAT3 and p38 signaling circuits. SIGNIFICANCE STATEMENT: This study demonstrates that chemical inhibition of PTP4A phosphatase activity with JMS-053 decreases STAT3 activation and increases SHP-2 phosphatase and p38 kinase phosphorylation activation in ovarian cancer cells. The newly developed JMS-053-resistant ovarian cancer cells should provide useful tools to further probe the role of PTP4A phosphatase in ovarian cancer cell survival and cell signaling.

HERPUD1 promotes ovarian cancer cell survival by sustaining autophagy and inhibit apoptosis via PI3K/AKT/mTOR and p38 MAPK signaling pathways

HERPUD1 is an important early marker of endoplasmic reticulum stress (ERS) and is involved in the ubiquitination and degradation of several unfolded proteins. However, its role in tumorigenesis is seldom studied, and its role in ovarian cancer is unclear. Lewis y antigen is a tumor-associated sugar antigen that acts as an ‘antenna’ on the cell surface to receive signals from both inside and outside the cell. We previously reported that Lewis y can promote ovarian cancer by promoting autophagy and inhibiting apoptosis. In this study, we detect the expression of HERPUD1 and Lewis y antigens in 119 different ovarian cancer tissues, determine their relationship with clinicopathological parameters, analyze the correlation between these two proteins, and explore the related cancer-promoting mechanisms through MTT, flow cytometry, western blotting, and bioinformatics. HERPUD1 is highly expressed in ovarian cancer, especially in the early stage, and the expression of HERPUD1 and Lewis y antigen was positively correlated. After overexpression of Lewis y antigen, the expression level of HERPUD1 increased. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes pathways (KEGG) analysis showed that HERPUD1 and its related genes are enriched in regulating immunity, endoplasmic reticulum stress, ubiquitin-dependent degradation, ERS-induced apoptosis, and other key signaling pathways. We also clarified the HERPUD1 network of kinases, microRNA and transcription factor targets, and the impact of HERPUD1 mutations on prognosis. In addition, HERPUD1 promotes the proliferation of ovarian cancer cells, inhibits apoptosis, affects the cell cycle, promotes the occurrence of autophagy, and inhibits EMT and PI3K/AKT/mTOR and p38MAPK pathways. Overall, HERPUD1, regulated by the expression of tumor-associated protein Lewis y, promotes cell survival in the early stages of tumors, suggesting that HERPUD1 may play an important role in the development of ovarian cancer.

FAP is critical for ovarian cancer cell survival by sustaining NF-κB activation through recruitment of PRKDC in lipid rafts.

Fibroblast activation protein (FAP) is tumor-specific and plays an important role in tumorigenecity. However, agents against its enzymatic activity or extracellular presence were unsuccessful in the clinic for undefined reasons. Here we show that FAP expression is higher in advanced ovarian cancer and is only detected in invasive ovarian cancer cells. Silencing FAP induces apoptosis and FAP's enzymatic activity is dispensable for cell survival. To elucidate the cause of apoptosis, we find that NF-κB activity is diminished when FAP is depleted and BIRC5 (survivin) acts downstream of FAP-NF-κB axis to promote cell survival. To uncover the link between FAP and NF-κB activation, we reveal that PRKDC (DNA-PK, DNA-dependent protein kinase) forms complex with FAP and is required for NF-κB activation and cell survival. Remarkably, FAP-PRKDC interaction occurs only in lipid rafts, and depleting FAP prevents lipid raft localization of PRKDC. Given the known ability of PRKDC to direct NF-κB activation, these results suggest that FAP recruits PRKDC in lipid rafts for NF-κB activation. FAP's non-enzymatic role and functioning from lipid rafts for cell survival also offer an explanation on the failure of past FAP-targeted therapies. Finally, we demonstrate that EpCAM aptamer-delivered FAP siRNA impeded intraperitoneal xenograft development of ovary tumors.

Agent-based modeling predicts RAC1 is critical for ovarian cancer metastasis.

Experimental and computational studies pinpoint rate-limiting step(s) in metastasis governed by Rac1. Using ovarian cancer cell and animal models, Rac1 expression was manipulated, and quantitative measurements of cell-cell and cell-substrate adhesion, cell invasion, mesothelial clearance, and peritoneal tumor growth discriminated the tumor behaviors most highly influenced by Rac1. The experimental data were used to parameterize an agent-based computational model simulating peritoneal niche colonization, intravasation, and hematogenous metastasis to distant organs. Increased ovarian cancer cell survival afforded by the more rapid adhesion and intravasation upon Rac1 overexpression is predicted to increase the numbers of and the rates at which tumor cells are disseminated to distant sites. Surprisingly, crowding of cancer cells along the blood vessel was found to decrease the numbers of cells reaching a distant niche irrespective of Rac1 overexpression or knockdown, suggesting that sites for tumor cell intravasation are rate limiting and become accessible if cells intravasate rapidly or are displaced due to diminished viability. Modeling predictions were confirmed through animal studies of Rac1-dependent metastasis to the lung. Collectively, the experimental and modeling approaches identify cell adhesion, rapid intravasation, and survival in the blood as parameters in the ovarian metastatic cascade that are most critically dependent on Rac1.

SIRT3 supports anchorage-independent survival of ovarian cancer cells by regulating mitochondrial redox signaling

SIRT3 supports anchorage-independent survival of ovarian cancer cells by regulating mitochondrial redox signaling

Splicing factor BUD31 promotes ovarian cancer progression through sustaining the expression of anti-apoptotic BCL2L12

Dysregulated expression of splicing factors has important roles in cancer development and progression. However, it remains a challenge to identify the cancer-specific splicing variants. Here we demonstrate that spliceosome component BUD31 is increased in ovarian cancer, and its higher expression predicts worse prognosis. We characterize the BUD31-binding motif and find that BUD31 preferentially binds exon-intron regions near splicing sites. Further analysis reveals that BUD31 inhibition results in extensive exon skipping and a reduced production of long isoforms containing full coding sequence. In particular, we identify BCL2L12, an anti-apoptotic BCL2 family member, as one of the functional splicing targets of BUD31. BUD31 stimulates the inclusion of exon 3 to generate full-length BCL2L12 and promotes ovarian cancer progression. Knockdown of BUD31 or splice-switching antisense oligonucleotide treatment promotes exon 3 skipping and results in a truncated isoform of BCL2L12 that undergoes nonsense-mediated mRNA decay, and the cells subsequently undergo apoptosis. Our findings reveal BUD31-regulated exon inclusion as a critical factor for ovarian cancer cell survival and cancer progression.

Ovarian cancer cell fate regulation by the dynamics between saturated and unsaturated fatty acids

Fatty acids are an important source of energy and a key component of phospholipids in membranes and organelles. Saturated fatty acids (SFAs) are converted into unsaturated fatty acids (UFAs) by stearoyl Co-A desaturase (SCD), an enzyme active in cancer. Here, we studied how the dynamics between SFAs and UFAs regulated by SCD impacts ovarian cancer cell survival and tumor progression. SCD depletion or inhibition caused lower levels of UFAs vs. SFAs and altered fatty acyl chain plasticity, as demonstrated by lipidomics and stimulated Raman scattering (SRS) microscopy. Further, increased levels of SFAs resulting from SCD knockdown triggered endoplasmic reticulum (ER) stress response with brisk activation of IRE1α/XBP1 and PERK/eIF2α/ATF4 axes. Disorganized ER membrane was visualized by electron microscopy and SRS imaging in ovarian cancer cells in which SCD was knocked down. The induction of long-term mild ER stress or short-time severe ER stress by the increased levels of SFAs and loss of UFAs led to cell death. However, ER stress and apoptosis could be readily rescued by supplementation with UFAs and reequilibration of SFA/UFA levels. The effects of SCD knockdown or inhibition observed invitro translated into suppression of intraperitoneal tumor growth in ovarian cancer xenograft models. Furthermore, a combined intervention using an SCD inhibitor and an SFA-enriched diet initiated ER stress in tumors growing invivo and potently blocked their dissemination. In all, our data support SCD as a key regulator of the cancer cell fate under metabolic stress and point to treatment strategies targeting the lipid balance.

Pigment epithelium-derived factor promotes peritoneal dissemination of ovarian cancer through induction of immunosuppressive macrophages

Peritoneal dissemination of ovarian cancer (OC) correlates with poor prognosis, but the mechanisms underlying the escape of OC cells from the intraperitoneal immune system have remained unknown. We here identify pigment epithelium–derived factor (PEDF) as a promoting factor of OC dissemination, which functions through induction of CD206+ Interleukin-10 (IL-10)–producing macrophages. High PEDF gene expression in tumors is associated with poor prognosis in OC patients. Concentrations of PEDF in ascites and serum are significantly higher in OC patients than those with more benign tumors and correlated with early recurrence of OC patients, suggesting that PEDF might serve as a prognostic biomarker. Bromodomain and extraterminal (BET) inhibitors reduce PEDF expression and limit both OC cell survival and CD206+ macrophage induction in the peritoneal cavity. Our results thus implicate PEDF as a driver of OC dissemination and identify a BET protein–PEDF–IL-10 axis as a promising therapeutic target for OC.

Abstract 5183: LGR5 CAR-T cells: A novel potential treatment against high grade serous ovarian cancer

Abstract Ovarian cancer is second leading cause of cancer-related mortality among gynecological cancers in the Western world. Although initial responses to 1st line treatment is high, over 75% of patients eventually relapse and acquire chemotherapy resistance, which is the primary cause of ovarian cancer treatment failure. New therapies to improve patient outcome are therefore urgently required. Chimeric antigen receptor T (CAR-T) cell therapy is an adoptive immunotherapy that is currently being used to treat some blood cancers. CAR-T cell therapies have so far been less effective against solid cancers, due in part to the absence of suitable tumor-associated antigen (TAA).This study has investigated whether Leucine-rich repeat-containing G protein-coupled receptor 5, LGR5) is a suitable target for CAR-T cell therapy for ovarian cancer. We found that LGR5 is highly expressed in HGSOC cancer lines (COV318, COV362 and OAW28) and increased in HGSOC tissues following relapse with chemotherapy resistant disease. We assessed the cytotoxic effects of LGR5-CAR-T cells on a range of ovarian cancer cell lines and primary serous ovarian cancer cells derived from patient ascites in vitro by MTT and 3D spheroid assays. We demonstrated that LGR5-CAR-T cells were cytotoxic and significantly inhibited survival of ovarian cancer cell lines (COV318, COV362) that express high levels of LGR5 but not SKOV3 or OV90 that express lower LGR5 levels in monolayer culture. In addition, LGR5-CAR-T cells were cytotoxic and significantly inhibited survival of primary serous ovarian cancer cells compared to un-transduced CD3+ T cells. LGR5 CAR-T cells also exhibited anti-tumor activity against ovarian cancer cell lines (COV318, COV362 & OAW28) and primary serous ovarian cancer cells in vitro using 3D-spheroid culture assays. This study demonstrates that LGR5-CAR-T cells have great potential to be developed as a novel immunotherapy for ovarian cancer. Citation Format: Wanqi Wang, Veronika Bandara, Noor Lokman, Silvana Napoli, Batjargal Gundsambuu, Martin Oehler, Simon C. Barry, Carmela Ricciardelli. LGR5 CAR-T cells: A novel potential treatment against high grade serous ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5183.

Abstract 128: SIRT3 supports anchorage-independent survival of ovarian cancer cells

Abstract Metabolic changes during tumor progression have numerous consequences on cancer cells, including an increased risk of cell death due to production of reactive oxygen species (ROS). Antioxidant defense adaptations thus accompany metabolic alterations as essential survival mechanisms during metastasis. We observe that oxidative phosphorylation is increased when ovarian cancer (OC) cells transition to anchorage independence (a-i), an important step during metastasis in the peritoneal cavity. To combat the rise in oxidative stress resulting from this metabolic shift, a rapid increase in the sirtuin 3 (SIRT3)/superoxide dismutase 2 (SOD2) axis occurs to reduce the mitochondrial superoxide anion surge and to maintain cellular viability. We demonstrate that this upregulation occurs in transcription, translation, and SIRT3-mediated regulation of SOD2 activity. However, the fate of the hydrogen peroxide (H2O2) resulting from superoxide dismutation through SIRT3/SOD2 remains unknown. RNAseq analysis of attached versus a-i conditions revealed a significant downregulation of peroxiredoxin 3, a major scavenger of H2O2 in the mitochondria, suggesting that OCs have a net increase in mitochondrial H2O2 in a-i. At sub-lethal levels, H2O2 serves as a second messenger of redox signaling, primarily via protein cysteine oxidation, which has been implicated with metastasis. We thus hypothesize that increases in SIRT3/SOD2/H2O2 play a role as mediators of redox signaling during OC anchorage-independent survival, spheroid formation and metastasis. Using the HyPer7 redox probe and manipulation of SIRT3 and SOD2 expression, H2O2 generation and localization in a-i are being assessed using 3D fluorescence microscopy. Moreover, siRNA mediated knock-down of SIRT3 in a-i leads to the downregulation of genes involved in specific signaling pathways, including NF-kB signaling, the inflammatory response, and metabolism. Mass-spec studies are underway to identify specific SIRT3 target proteins upstream of these transcriptional changes, by assessing global cysteine oxidation and the cellular acetylome to determine the role of H2O2-dependent redox signaling and SIRT3-dependent protein de-acetylation, respectively. Given the increase in SIRT3-dependent inflammatory signaling in a-i, we are exploring how the SIRT3/SOD2/H2O2 axis influences OC interaction with tumor associated macrophages and mesenchymal stem cells, commonly found in the ascites tumor environment. This work demonstrates a multi-faceted role for the SIRT3/SOD2/H2O2 axis in a-i survival, a key step during OC metastasis. Citation Format: Priscilla Tang, Yeon Soo Kim, Piyushi Gupta-Vallur, Amal T. Elhaw, Zaineb Javed, Weihua Pan, Nadine Hempel. SIRT3 supports anchorage-independent survival of ovarian cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 128.