Resistant Ovarian Cancer Research Articles

OTUB2 silencing promotes ovarian cancer via mitochondrial metabolic reprogramming and can be synthetically targeted by CA9 inhibition

Ovarian cancer is an aggressive gynecological tumor characterized by a high relapse rate and chemoresistance. Ovarian cancer exhibits the cancer hallmark of elevated glycolysis, yet effective strategies targeting cancer cell metabolic reprogramming to overcome therapeutic resistance in ovarian cancer remain elusive. Here, we revealed that epigenetic silencing of Otubain 2 (OTUB2) is a driving force for mitochondrial metabolic reprogramming in ovarian cancer, which promotes tumorigenesis and chemoresistance. Mechanistically, OTUB2 silencing destabilizes sorting nexin 29 pseudogene 2 (SNX29P2), which subsequently prevents hypoxia-inducible factor-1 alpha (HIF-1α) from von Hippel-Lindau tumor suppressor-mediated degradation. Elevated HIF-1α activates the transcription of carbonic anhydrase 9 (CA9) and drives ovarian cancer progression and chemoresistance by promoting glycolysis. Importantly, pharmacological inhibition of CA9 substantially suppressed tumor growth and synergized with carboplatin in the treatment of OTUB2-silenced ovarian cancer. Thus, our study highlights the pivotal role of OTUB2/SNX29P2 in suppressing ovarian cancer development and proposes that targeting CA9-mediated glycolysis is an encouraging strategy for the treatment of ovarian cancer.

Expression of human dCTP pyrophosphatase 1 (DCTPP1) and its association with cisplatin resistance characteristics in ovarian cancer.

Cisplatin (DDP) resistance is a major challenge in treating ovarian cancer patients. A recently discovered enzyme called dCTP pyrophosphatase 1 (DCTPP1) has been implicated in regulating cancer characteristics, including drug responses. In this study, we aimed to understand the role of DCTPP1 in cancer progression and cisplatin response. Using publicly available databases, we analysed the expression and clinical significance of DCTPP1 in ovarian cancer. Our bioinformatics analysis confirmed that DCTPP1 is significantly overexpressed in ovarian cancer and is closely associated with tumour progression and poor prognosis after cisplatin treatment. We also found that DCTPP1 located in oxidoreductase complex and may be involved in various biological processes related to cisplatin resistance, including pyrimidine nucleotide metabolism, the P53 signalling pathway and cell cycle signalling pathways. We observed higher expression of DCTPP1 in cisplatin-resistant cells (SKOV3/DDP) and samples compared to their sensitive counterparts. Additionally, we found that DCTPP1 expression was only enhanced in SKOV3/S cells when treated with cisplatin, indicating different expression patterns of DCTPP1 in cisplatin-sensitive and cisplatin-resistant cancer cells. Our study further supports the notion that cisplatin induces intracellular reactive oxygen species (ROS) and triggers cancer cell death through excessive oxidative stress. Knocking out DCTPP1 reversed the drug resistance of ovarian cancer cells by enhancing the intracellular antioxidant stress response and accumulating ROS. Based on our research findings, we conclude that DCTPP1 has prognostic value for ovarian cancer patients, and targeting DCTPP1 may be clinically significant in overcoming cisplatin resistance in ovarian cancer.

MAP7 drives EMT and cisplatin resistance in ovarian cancer via wnt/β-catenin signaling

MethodsOur approach encompasses analyzing MAP7's expression levels across various datasets and clinical specimens, evaluating its association with patient outcomes, and probing its influence on ovarian cancer cell dynamics such as proliferation, migration, invasion, and apoptosis. ResultsWe have identified significant upregulation of MAP7 in ovarian cancer tissues, which correlates with advanced disease stages, higher pathological grades, and unfavorable prognoses. Functionally, the inhibition of MAP7 suppresses cancer cell proliferation, migration, and invasion while promoting apoptosis. Notably, the silencing of MAP7 attenuates the epithelial-mesenchymal transition (EMT) and disrupts Wnt/β-catenin pathway signaling—two critical processes implicated in metastasis and chemoresistance. In cisplatin-resistant A2780-DDP cells, the downregulation of MAP7 effectively reverses their resistance to cisplatin. Furthermore, the nuclear localization of MAP7 in these cells underscores its pivotal role in driving cisplatin resistance by modulating the transcriptional regulation and interaction dynamics of β-catenin. ConclusionOur findings position MAP7 as a pivotal element in ovarian cancer advancement and cisplatin resistance, primarily through its modulation of EMT and the Wnt/β-catenin pathway. Its association with poor clinical outcomes underscores its potential as both a prognostic marker and a therapeutic target. Strategies aimed at MAP7 could represent a new frontier in combating chemotherapy resistance in ovarian cancer, emphasizing its significance in crafting complementary treatments for this disease.

RAD51 as an immunohistochemistry-based marker of poly(ADP-ribose) polymerase inhibitor resistance in ovarian cancer.

Effective functional biomarkers that can be readily used in clinical practice to predict poly(ADP-ribose) polymerase inhibitor (PARPi) sensitivity are lacking. With the widespread adoption of PARPi maintenance therapy in ovarian cancer, particularly in patients with BRCA mutation or HR deficiencies, accurately identifying de novo or acquired resistance to PARPi has become critical in clinical practice. We investigated RAD51 immunohistochemistry (IHC) as a functional biomarker for predicting PARPi sensitivity in ovarian cancer. Ovarian cancer patients who had received PARPi and had archival tissue samples prior to PARPi exposure ("pre-PARPi") and/or after progression on PARPi ("post-PARPi") were selected. RAD51 IHC expression was semi-quantitatively evaluated using the H-score in geminin (a G2/S phase marker)- and γH2AX (a DNA damage marker)-positive tissues. A RAD51 H-score of 20 was used as the cutoff value. In total, 72 samples from 56 patients were analyzed. The median RAD51 H-score was 20 (range: 0-90) overall, 10 (0-190) in pre-PARPi samples (n = 34), and 25 (1-170) in post-PARPi samples (n = 19). Among patients with BRCA mutations, RAD51-low patients had better progression-free survival (PFS) after PARPi treatment than RAD51-high patients (P = 0.029). No difference was found in PFS with respect to the genomic scar score (P = 0.930). Analysis of matched pre- and post-PARPi samples collected from 15 patients indicated an increase in the RAD51 H-score upon progression on PARPi, particularly among pre-PARPi low-RAD51-expressing patients. RAD51 is a potential functional IHC biomarker of de novo and acquired PARPi resistance in BRCA-mutated ovarian cancer and can be used to fine-tune ovarian cancer treatment.

TCEB3 initiates ovarian cancer apoptosis by mediating ubiquitination and degradation of MCL-1.

Platinum resistance remains a major contributor to the poor prognosis of ovarian cancer. Anti-apoptotic protein myeloid cell leukemia-1 (MCL-1) has emerged as a promising target for overcoming drug resistance, but different cancer cells utilize distinct protein degradation pathways to alter MCL-1 level. We systematically investigated E3 ligases to identify novel candidates that mediate platinum resistance in ovarian cancer. Transcription Elongation Factor B (TCEB3) has been identified as a novel E3 ligase recognition subunit that targets MCL-1 in the cytoplasm during platinum treatment other than its traditional function of targeting the Pol II in the nuclear compartment. TCEB3 expression is downregulated in platinum-resistant cell lines and this low expression is associated with poor prognosis. The ubiquitination of MCL-1 induced by TCEB3 leads to cell death in ovarian cancer. Moreover, platinum treatment increased the cytoplasm proportion of TCEB3, and the cytoplasm localization of TCEB3 is important for its targeting of MCL-1. This study emphasizes the dual function of TCEB3 in homeostasis maintenance and in cell fate determination under different conditions, and provides a new insight into drug resistance in ovarian cancer.

Platinum-induced upregulation of ITGA6 promotes chemoresistance and spreading in ovarian cancer

Platinum (PT)-resistant Epithelial Ovarian Cancer (EOC) grows as a metastatic disease, disseminating in the abdomen and pelvis. Very few options are available for PT-resistant EOC patients, and little is known about how the acquisition of PT-resistance mediates the increased spreading capabilities of EOC. Here, using isogenic PT-resistant cells, genetic and pharmacological approaches, and patient-derived models, we report that Integrin α6 (ITGA6) is overexpressed by PT-resistant cells and is necessary to sustain EOC metastatic ability and adhesion-dependent PT-resistance. Using in vitro approaches, we showed that PT induces a positive loop that, by stimulating ITGA6 transcription and secretion, contributes to the formation of a pre-metastatic niche enabling EOC cells to disseminate. At molecular level, ITGA6 engagement regulates the production and availability of insulin-like growth factors (IGFs), over-stimulating the IGF1R pathway and upregulating Snail expression. In vitro data were recapitulated using in vivo models in which the targeting of ITGA6 prevents PT-resistant EOC dissemination and improves PT-activity, supporting ITGA6 as a promising druggable target for EOC patients.

Extracellular vesicles of Bifidobacterium longum reverse the acquired carboplatin resistance in ovarian cancer cells via p53 phosphorylation on Ser15.

We previously found that the relative abundance of Bifidobacterium was increased after chemotherapy; however, the role of Bifidobacterium longum in chemotherapeutic drug resistance in ovarian cancer (OVC) remains unclear. This study aimed to understand the potential effects and mechanism of B. longum extracellular vesicles (B. longum-EVs) on carboplatin (CBP) resistance in OVC. Eight normal and 11 ovarian tissues were collected and the expression of B. longum genomic DNA and its association with acquired CBP resistance in OVC patients was determined. After isolating EVs by ultracentrifugation from B. longum (ATCC 15707), CBP-resistant A2780 cells were treated with PBS, CBP, B. longum-EVs, or CBP + B. longum-EVs, and subsequently analyzed by CCK-8, Edu staining, Annexin V/PI double staining, wound healing, and Transwell assays to detect cell viability, proliferation, apoptosis, migration, and invasion, respectively. MRP1, ATP7A, ATP7B, and p53 expression as well as p53 phosphorylation were measured by western blot analysis. S15A mutation of p53 was assessed to examine the potential role of p53 Ser15 phosphorylation in CBP-resistant OVC. B. longum levels were elevated and positively associated with CBP resistance in OVC patients. Only high concentrations of B. longum-EVs attenuated A2780 cell proliferation, apoptosis, migration, and invasion. B. longum-EVs exposure significantly enhanced the sensitivity of CBP-resistant A2780 cells to CBP and decreased the expression of drug resistance-related proteins. The effect of B. longum-EVs on reversing CBP resistance was completely inhibited by S15A mutation of p53. B. longum-EVs enhanced the sensitivity of OVC cells to CBP through p53 phosphorylation on Ser15.

Harnessing Antitumor Immunity in Ovarian Cancer.

Despite progress in other tumor types, immunotherapy is not yet part of the standard of care treatment for high-grade serous ovarian cancer patients. Although tumor infiltration by T cells is frequently observed in patients with ovarian cancer, clinical responses to immunotherapy remain low. Mechanisms for immune resistance in ovarian cancer have been explored and may provide insight into future approaches to improve response to immunotherapy agents. In this review, we discuss what is known about the immune landscape in ovarian cancer, review the available data for immunotherapy-based strategies in these patients, and provide possible future directions.

Targeting PNPO to suppress tumor growth via inhibiting autophagic flux and to reverse paclitaxel resistance in ovarian cancer

Our previous study showed that pyridoxine 5’-phosphate oxidase (PNPO) is a tissue biomarker of ovarian cancer (OC) and has a prognostic implication but detailed mechanisms remain unclear. The current study focused on PNPO-regulated lysosome/autophagy-mediated cellular processes and the potential role of PNPO in chemoresistance. We found that PNPO was overexpressed in OC cells and was a prognostic factor in OC patients. PNPO significantly promoted cell proliferation via the regulation of cyclin B1 and phosphorylated CDK1 and shortened the G2M phase in a cell cycle. Overexpressed PNPO enhanced the biogenesis and perinuclear distribution of lysosomes, promoting the degradation of autophagosomes and boosting the autophagic flux. Further, an autolysosome marker LAMP2 was upregulated in OC cells. Silencing LAMP2 suppressed cell growth and induced cell apoptosis. LAMP2-siRNA blocked PNPO action in OC cells, indicating that the function of PNPO on cellular processes was mediated by LAMP2. These data suggest the existence of the PNPO-LAMP2 axis. Moreover, silencing PNPO suppressed xenographic tumor formation. Chloroquine counteracted the promotion effect of PNPO on autophagic flux and inhibited OC cell survival, facilitating the inhibitory effect of PNPO-shRNA on tumor growth in vivo. Finally, PNPO was overexpressed in paclitaxel-resistant OC cells. PNPO-siRNA enhanced paclitaxel sensitivity in vitro and in vivo. In conclusion, PNPO has a regulatory effect on lysosomal biogenesis that in turn promotes autophagic flux, leading to OC cell proliferation, and tumor formation, and is a paclitaxel-resistant factor. These data imply a potential application by targeting PNPO to suppress tumor growth and reverse PTX resistance in OC.

Abstract CT139: Immunological activity of oncolytic adenovirus encoding TNFα and IL-2 (TILT-123) in combination with pembrolizumab in platinum resistant or refractory ovarian cancer patients

Abstract Background TILT-123 (Ad5/3-E2F-D24-hTNFα-IRES-hIL-2) is a serotype chimeric dual safety device oncolytic adenovirus armed with tumor necrosis factor alpha and interleukin-2. It was designed to improve efficacy of T-cell therapies such as immune checkpoint blockade or adoptive cell transfer. We present biological and immunological endpoints from an open-label phase 1 dose escalation study of TILT-123 in combination with anti-PD-1 pembrolizumab in platinum resistant or refractory ovarian cancer patients. Experimental procedures In this dose escalation trial (NCT05271318), patients were first injected with an intravenous (i.v.) dose of TILT-123 ranging from 3x1011 to 4x1012 virus particles (VP), followed by five intratumoural (i.t.) or intraperitoneal (i.p.) injections ranging from 1x1011 to 5x1011 VP. Patients also received intravenous injections of 200 mg pembrolizumab every three weeks starting 36 days after the first dose of TILT-123. The primary endpoint was safety, while efficacy by RECIST1.1 was a secondary endpoint. Collection of tumor biopsies, circulating immune cells, serum, saliva, urine and feces enabled multi-omic evaluation of mechanism of action and identification of predictive biomarkers. Summary of data As of January 2nd 2024, 15 patients received trial therapy. No dose-limiting toxicities were observed and the most frequent AEs associated with therapy included chills and nausea (>10% of patients). Stable disease by RECIST 1.1 was seen in 67% in 12 evaluable patients. TILT-123 replication was detected in both injected and non-injected tumors as assessed by qPCR and anti-hexon IHC. Multiplex immunofluorescence demonstrated induction of robust immunological activity in both injected and non-injected tumors, including significant increase in granzyme B+, PD-1+ CD4+ and CD8+ T cells as well as PD-1+ NK cells. Baseline intratumoral CD4+, FOXP3+ regulatory T cells were not associated with clinical response. Tertiary lymphoid structures and lymphoid aggregates were identified in patients showing long term disease control. Low to medium titers of neutralizing antibodies against 5/3 chimeric adenovirus were detected in 57% of patients at baseline and were not a predictive factor of disease control. No patients had high titers at baseline. Conclusion TILT-123 in combination with anti-PD-1 pembrolizumab was safe and resulted in disease control in both platinum resistant and refractory ovarian cancer patients. Analysis of biological samples revealed insights into mechanism of action, including an immune profile predictive of clinical response. These results, together with those from four other trials (NCT04695327, NCT04217473, NCT06125197 and NCT05222932) set the stage for continued clinical evaluation of TILT-123. Citation Format: James H. Clubb, Matthew S. Block, Johanna Mäenpää, Santeri Pakola, Lyna Haybout, Dafne C. Quixabeira, Tatiana Kudling, Mirte van der Heijden, Elise Jirovec, Tuomo Alanko, Daniel A. Adamo, Susan Ramadan, Jorma Sormunen, Juha Kononen, Julia W. Cohen, Nadena Singh, John Goldfinch, Suvi Sorsa, Riikka Havunen, Claudia Kistler, João M. Santos, Víctor Cervera-Carrascon, Akseli Hemminki. Immunological activity of oncolytic adenovirus encoding TNFα and IL-2 (TILT-123) in combination with pembrolizumab in platinum resistant or refractory ovarian cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT139.

Comparison of Photodynamic Priming Efficacy, with BPD or ALA-PpIX, to Overcome PFAS-Induced Platinum Resistance in Ovarian Cancer

Ovarian cancer is the most lethal gynecologic cancer, largely due to the development of platinum-based chemotherapy resistance. Understanding sources of chemoresistance and the development of mechanism-based treatments are critical. In a recent study, we reported that perfluoroalkyl substances (PFAS), endocrine disruptors that pollute drinking water supplies worldwide, induce carboplatin resistance in ovarian cancer cells, potentially by enhancing mitochondrial function. The ability of photodynamic priming (PDP) to overcome PFAS-induced resistance using photosensitizers that, in part, localize to mitochondria, specifically benzoporphyrin derivative (BPD) or aminolevulinic acid-induced protoporphyrin IX (ALA-PpIX)), will be presented. Ovarian cancer cells were exposed to PFAS, then treated with either BPD- or ALA-PpIX-PDP followed by carboplatin. Under PFAS exposure conditions that previously induced chemoresistance, both BPD- and ALA-PpIX-PDP sensitized ovarian cancer cells to carboplatin. A concomitant decrease in mitochondrial membrane potential was observed.

Long noncoding RNA TUG1 promotes cisplatin resistance in ovarian cancer via upregulation of DNA polymerase eta.

Chemoresistance is a major cause of high mortality and poor survival in patients with ovarian cancer (OVCA). Understanding the mechanisms of chemoresistance is urgently required to develop effective therapeutic approaches to OVCA. Here, we show that expression of the long noncoding RNA, taurine upregulated gene 1 (TUG1), is markedly upregulated in samples from OVCA patients who developed resistance to primary platinum-based therapy. Depletion of TUG1 increased sensitivity to cisplatin in the OVCA cell lines, SKOV3 and KURAMOCHI. Combination therapy of cisplatin with antisense oligonucleotides targeting TUG1 coupled with a drug delivery system effectively relieved the tumor burden in xenograft mouse models. Mechanistically, TUG1 acts as a competing endogenous RNA by downregulating miR-4687-3p and miR-6088, both of which target DNA polymerase eta (POLH), an enzyme required for translesion DNA synthesis. Overexpression of POLH reversed the effect of TUG1 depletion on cisplatin-induced cytotoxicity. Our data suggest that TUG1 upregulation allows OVCA to tolerate DNA damage via upregulation of POLH; this provides a strong rationale for targeting TUG1 to overcome cisplatin resistance in OVCA.

Targeting the Cdc2-like kinase 2 for overcoming platinum resistance in ovarian cancer.

Platinum resistance represents a major barrier to the survival of patients with ovarian cancer (OC). Cdc2-like kinase 2 (CLK2) is a major protein kinase associated with oncogenic phenotype and development in some solid tumors. However, the exact role and underlying mechanism of CLK2 in the progression of OC is currently unknown. Using microarray gene expression profiling and immunostaining on OC tissues, we found that CLK2 was upregulated in OC tissues and was associated with a short platinum-free interval in patients. Functional assays showed that CLK2 protected OC cells from platinum-induced apoptosis and allowed tumor xenografts to be more resistant to platinum. Mechanistically, CLK2 phosphorylated breast cancer gene 1 (BRCA1) at serine 1423 (Ser1423) to enhance DNA damage repair, resulting in platinum resistance in OC cells. Meanwhile, in OC cells treated with platinum, p38 stabilized CLK2 protein through phosphorylating at threonine 343 of CLK2. Consequently, the combination of CLK2 and poly ADP-ribose polymerase inhibitors achieved synergistic lethal effect to overcome platinum resistance in patient-derived xenografts, especially those with wild-type BRCA1. These findings provide evidence for a potential strategy to overcome platinum resistance in OC patients by targeting CLK2.

A Stem-like Patient-Derived Ovarian Cancer Model of Platinum Resistance Reveals Dissociation of Stemness and Resistance.

To understand chemoresistance in the context of cancer stem cells (CSC), a cisplatin resistance model was developed using a high-grade serous ovarian cancer patient-derived, cisplatin-sensitive sample, PDX4. As a molecular subtype-specific stem-like cell line, PDX4 was selected for its representative features, including its histopathological and BRCA2 mutation status, and exposed to cisplatin in vitro. In the cisplatin-resistant cells, transcriptomics were carried out, and cell morphology, protein expression, and functional status were characterized. Additionally, potential signaling pathways involved in cisplatin resistance were explored. Our findings reveal the presence of distinct molecular signatures and phenotypic changes in cisplatin-resistant PDX4 compared to their sensitive counterparts. Surprisingly, we observed that chemoresistance was not inherently linked with increased stemness. In fact, although resistant cells expressed a combination of EMT and stemness markers, functional assays revealed that they were less proliferative, migratory, and clonogenic-features indicative of an underlying complex mechanism for cell survival. Furthermore, DNA damage tolerance and cellular stress management pathways were enriched. This novel, syngeneic model provides a valuable platform for investigating the underlying mechanisms of cisplatin resistance in a clinically relevant context, contributing to the development of targeted therapies tailored to combat resistance in stem-like ovarian cancer.

MicroRNA Expression Profiles in Human Samples and Cell Lines Revealed Nine miRNAs Associated with Cisplatin Resistance in High-Grade Serous Ovarian Cancer.

Metastasis and drug resistance are major contributors to cancer-related fatalities worldwide. In ovarian cancer (OC), a staggering 70% develop resistance to the front-line therapy, cisplatin. Despite proposed mechanisms, the molecular events driving cisplatin resistance remain unclear. Dysregulated microRNAs (miRNAs) play a role in OC initiation, progression, and chemoresistance, yet few studies have compared miRNA expression in OC samples and cell lines. This study aimed to identify key miRNAs involved in the cisplatin resistance of high-grade-serous-ovarian-cancer (HGSOC), the most common gynecological malignancy. MiRNA expression profiles were conducted on RNA isolated from formalin-fixed-paraffin-embedded human ovarian tumor samples and HGSOC cell lines. Nine miRNAs were identified in both sample types. Targeting these with oligonucleotide miRNA inhibitors (OMIs) reduced proliferation by more than 50% for miR-203a, miR-96-5p, miR-10a-5p, miR-141-3p, miR-200c-3p, miR-182-5p, miR-183-5p, and miR-1206. OMIs significantly reduced migration for miR-183-5p, miR-203a, miR-296-5p, and miR-1206. Molecular pathway analysis revealed that the nine miRNAs regulate pathways associated with proliferation, invasion, and chemoresistance through PTEN, ZEB1, FOXO1, and SNAI2. High expression of miR-1206, miR-10a-5p, miR-141-3p, and miR-96-5p correlated with poor prognosis in OC patients according to the KM plotter database. These nine miRNAs could be used as targets for therapy and as markers of cisplatin response.

A Novel Synthesized Cyclohexane-Hydroxytyrosol Derivative Suppresses Ovarian Cancer Cell Growth Through Inducing Reactive Oxidative Species and Blocking Autophagic Flux.

Aims: Drug resistance in ovarian cancer (OC) cells often leads to recurrence, metastasis, and high mortality rates among OC patients. Hydroxytyrosol (HT) has been reported to inhibit the proliferation of ovarian and other types of cancer cells. Here we synthesized a novel cyclohexane-hydroxytyrosol derivative (Chx-HT) for enhanced anticaner efficacy. We examined the growth-suppressing effect of Chx-HT on OC cells in vitro and in a xenograft mouse model and investigated the underlying mechanism. Results: We demonstrated that Chx-HT inhibits proliferation, promotes apoptosis, and remodels glucose and lipid metabolism by reducing fatty acid β-oxidation while increasing glycolysis, de novo fatty acid synthesis (FAS), and lipid droplet (LD) accumulation, impairs mitochondrial respiration, and induces oxidative stress both in vitro and in vivo. In addition, Chx-HT blocks autophagic flux by obstructing the maturation of lysosomal cathepsins in the late stage, but also activates autophagy through the p-AMPK/p-mTOR/p-ULK1 pathway in response to energy deficit. Innovation and Conclusion: Reactive oxidative species (ROS) play a critical role in mediating the effects of Chx-HT on proliferation, apoptosis, autophagy, tricarboxylic acid (TCA) cycle, fatty acid β-oxidation, and mitochondrial respiration, and the autophagic activation underlies the effects of Chx-HT on glycolysis, de novo FAS, and LD accumulation in OC cells. Cotreating OC cells with Chx-HT and autophagic inhibitor or glycolytic inhibitor results in an additive inhibition of proliferation. Our study indicates that Chx-HT stands for a promising OC therapeutic by ROS and autophagy blockade-mediated metabolic remodeling.

Drug resistance‑related gene targets and molecular mechanisms in the A2780/Taxol‑resistant epithelial ovarian cancer cell line.

Epithelial ovarian cancer (EOC) is a fatal gynecological malignant tumor with a low 5-year survival rate. The use of the first-line chemotherapeutic drug, paclitaxel, for the treatment of EOC is associated with resistance, often leading to treatment failure. The present study investigated the gene targets in an A2780 paclitaxel-resistant EOC cell line (A2780/Taxol), and the potential underlying mechanisms using transcriptome sequencing technology and bioinformatics analysis. The transcriptome of the A2780/Taxol cell line was sequenced, and 498 differentially expressed genes were obtained contained in the Gene Expression Omnibus dataset. Further bioinformatics analysis revealed that matrix metalloproteinase 1 (MMP1), zyxin (ZYX) and Unc-5 netrin receptor C (UNC5C) may be gene targets related to paclitaxel resistance. Moreover, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis indicated that a potential mechanism associated with paclitaxel resistance was related to cell migration. Furthermore, the expression levels of MMP1, ZYX and UNC5C were verified using western blotting, immunofluorescence and immunohistochemistry in vitro. The results revealed that the expression levels of MMP1 and ZYX were significantly increased in A2780/Taxol cells, while UNC5C expression was significantly decreased, which was consistent with the results of the transcriptome sequencing. The present study demonstrated that MMP1, ZYX and UNC5C may be the gene targets associated with paclitaxel resistance in EOC. These genes have potential to be used as molecular markers for EOC drug therapy, targeted elimination of drug resistance, and evaluation of treatment efficacy and patient prognosis.

CD147 facilitates cisplatin resistance in ovarian cancer through FOXM1 degradation inhibition

CD147 facilitates cisplatin resistance in ovarian cancer through FOXM1 degradation inhibition

Abstract 7155: Dichloroacetate reverses cisplatin resistance in ovarian cancer through promoting ROS production

Abstract Chemotherapy resistance and the high rate of ovarian cancer relapse pose major challenges in the treatment of ovarian cancer. The development of chemoresistance contributes to poor overall prognosis associated with ovarian cancer and high cancer-related mortality in women worldwide. Herein, we found that Dichloroacetate (DCA), a pan-pyruvate dehydrogenase kinase (PDK) inhibitor, is a potent agent to overcome Cisplatin (CP) resistance in ovarian cancer treatment. Firstly, we elucidated that phosphorylation of pyruvate dehydrogenase (pPDH) was elevated in CP-resistant ovarian cancer cells. Then, blockage of pPDH by DCA treatment significantly inhibited cell migratory and invasive capacity in CP-resistant ovarian cancer cells through the transition of motile mesenchymal phenotypes into epithelial characteristics. DCA markedly decreased the number of sphere formations and attenuated the stem cell-like properties in CP-resistant ovarian cancer cells. In combination with CP treatment, DCA effectively inhibited cell proliferation in chemoresistant ovarian cancer cells by triggering apoptosis. Collectively, we suggested that DCA is a promising drug to reverse CP resistance for ovarian cancer treatment. We further tested the underlying mechanisms of DCA to restore CP sensitivity in ovarian cancer. We found that CP treatment promoted reactive oxygen species (ROS) production to induce cell death in CP-sensitive ovarian cancer. However, CP-resistant ovarian cancer cells exhibited higher basal levels of ROS compared with sensitive cancer cells, and CP treatment failed to generate ROS production. That means ovarian cancer cells steadily adapted to elevated ROS levels, then becoming ROS-adapted ovarian cancer cells to survive. Interestingly, DCA treatment results in the buildup of ROS production, causing cell death in CP-resistant ovarian cancer. Therefore, our study suggests that ROS production can be an attractive target in DCA treatment to restore CP sensitivity in ovarian cancer. Citation Format: Yen Thi Do, Seungmee Lee, Changmin Shin, Hyewon Chung, Jin Young Kim, Eunyoung Ha, Sojin Shin, Ji Hae Seo. Dichloroacetate reverses cisplatin resistance in ovarian cancer through promoting ROS production [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7155.

Abstract 7557: Hypoxia-induced downregulation of MUC16: A key player in bispecific T-cell engager resistance in ovarian cancer

Abstract Background: Ovarian cancer (OC) is a lethal disease due to limited treatment options and the development of multidrug resistance. Bispecific T-cell engager (BiTE) therapy represents a promising immunotherapeutic approach to OC. Our previous findings suggest that resistance to BiTE therapy in OC is a complex interplay of factors including loss of tumor-associated antigens and epithelial-mesenchymal transition (EMT). Since the peritoneum is a relatively hypoxic (HX) tumor microenvironment, we hypothesized that HX plays a role in the modulation of MUC16 and potential resistance to BiTE therapy. Methods: After informed consent, samples were collected from patients with recurrent OC undergoing treatment with MUC16 BiTEs. For HX studies, we used OVCAR3 tumor cell lines which express full-length MUC16. Tumor cells were cultured under normoxic (NX) or HX conditions. The effect of HX on cell death was analyzed using an apoptosis assay. Cells were evaluated for changes in cell surface MUC16 expression by flow cytometry. MUC16 protein expression and EMT markers were analyzed by western blot. Proteasome inhibitors were used to stabilize MUC16 expression under HX conditions. Antibody internalization assays were conducted to assess MUC16 endocytosis and recycling. Results: In patients who progressed on MUC16 BiTEs, we found decreased MUC16 expression on tumor samples isolated from ascites samples. Using OVCAR3 cells, we found significantly decreased MUC16 expression on ovarian cancer cells grown under HX conditions (Fold change: 0.4 vs NX, p<0.001). Flow cytometry analysis revealed a time-dependent loss of MUC16 expression on the cell surface under HX (64.22% after 9 days HX vs 88.26% NX), highlighting the susceptibility of MUC16 to HX-induced downregulation. Treatment with proteasome inhibitors partially rescued MUC16 expression under HX conditions (Fold change: 1.4 vs NX, p<0.001). Notably, HX did not induce necrotic cell death in these tumor cells. In addition to the loss of MUC16, tumor cells under HX conditions showed alterations in EMT markers. E-cadherin was downregulated with prolonged HX exposure (Fold change: 0.3 vs NX, p < 0.001), while Vimentin (Fold change: 7.1 vs NX, p < 0.001) and Snail (Fold change: 2.8 vs NX, p < 0.001) were upregulated, indicating a potential shift towards a more aggressive phenotype. Epidermal growth factor receptor (EGFR) was also upregulated (Fold change: 4.9 vs NX, p < 0.001), potentially contributing to enhanced survival and invasion of OC cells under HX stress. Finally, under HX conditions, MUC16 internalization was slower in response to antibody binding over time due to reduced cell antigen expression, corroborating the observed MUC16 loss. Conclusion: Understanding hypoxia-induced MUC16 downregulation and its downstream effects on EMT markers and CA125 expression provides crucial insight into the mechanisms of BiTE therapy resistance in ovarian cancer. Citation Format: Mengyao Xu, Syem K. Barakzai, Artem Kononenko, Raj Kumar, Irva Veillard, Eugene Kim, Timothy S. Bond, David R. Spriggs, Bo R. Rueda, Oladapo Yeku. Hypoxia-induced downregulation of MUC16: A key player in bispecific T-cell engager resistance in ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7557.