Platinum Resistance In Ovarian Cancer Research Articles

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.

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.

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.

Abstract B100: Perfluoroalkyl substances (PFAS) induce platinum resistance in ovarian cancer through altering mitochondrial function

Abstract Platinum resistance is a major barrier to the effective treatment of advanced-stage ovarian cancer; however, factors leading to the development of resistance are not well understood. In fact, the role of environmental endocrine disrupting chemicals, such as perfluoroalkyl substances (PFAS), have seldom been explored. This is important because select PFAS have been linked to adverse reproductive outcomes in females including endometriosis, oocyte apoptosis, infertility, and increased even ovarian cancer risk at very high exposure levels. The relationship between PFAS and adverse female reproductive outcomes, as well as reports of other endocrine disruptors leading to therapy resistance, led, in the current study, to the evaluation of the effect of PFAS exposure on response to carboplatin in ovarian cancer cells. We recently showed that select PFAS, at human-relevant concentrations, induced carboplatin resistance in OVCAR-3 and Caov-3 cells; however, the mechanism underlying the onset of resistance remains largely unknown. Since platinum-resistant ovarian cancer is characterized, in part, by increased mitochondrial networks and enhanced bioenergetic capacities, the central hypothesis of this study is that PFAS induce alterations to mitochondrial biology. Mitochondrial endpoints of interest included redox ratio and superoxide production. To measure redox ratio, nicotinamide dinucleotide (NADH) and flavin adenine dinucleotide (FAD), which are inherently fluorescent, were measured using a fluorescence plate reader. Since NADH and FAD are metabolites produced via oxidative phosphorylation and glycolysis, evaluating redox ratio can provide an understanding of which pathway is preferred in the presence of environmental stimuli like PFAS. In OVCAR-3 and Caov-3 cells, baseline NADH:FAD ratios were 3.3 and 3.5, respectively. After 48 hours of PFAS exposure, NADH:FAD ratios of OVCAR-3 and Caov-3 cells ranged from 8-10 or 6-10, respectively. This increase after PFAS exposure could suggest enhanced energy production capabilities that warrant further investigation. As an additional measure, superoxide production was measured using flow cytometry. OVCAR-3 and Caov-3 cells were exposed to PFAS for 6 days prior to isolating cell pellets and incubating them with MitoSOX (mitochondrial) and SYTOX Blue (nuclear) dyes. After 15–30-minute incubations, samples were run on the flow cytometer. Compared to controls, superoxide production in PFAS-exposed ovarian cancer cells increased by up to 200%. Often, cancer cells have elevated levels of reactive oxygen species due to enhanced energy production and signaling pathways, thus this finding further suggests that PFAS affect mitochondrial energy pathways. Altogether, these data show that PFAS exposure, which can induce carboplatin resistance in OVCAR-3 and Caov-3 cells, increases redox ratios and superoxide production in ovarian cancer cells. Therefore, targeting alterations in mitochondrial biology arising from PFAS exposure using precision medicine could be effective in overcoming platinum resistance in ovarian cancer. Citation Format: Brittany P. Rickard, Marta Overchuk, Vesna A. Chappell, Carl D. Bortner, Victoria L. Bae-Jump, Suzanne E. Fenton, Imran Rizvi. Perfluoroalkyl substances (PFAS) induce platinum resistance in ovarian cancer through altering mitochondrial function [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 B100.

Abstract B111: Mechanism-informed photochemical strategies to overcome fluid shear stress-induced platinum resistance in ovarian cancer

Abstract Background: Over 75% of patients with disseminated ovarian cancer develop resistance to platinum-based chemotherapies (carboplatin or cisplatin). Patients with a high volume of malignant ascites or excessive fluid buildup in the peritoneum are more likely to present with primary platinum-resistant disease. It is hypothesized that the physical forces generated by ascites may contribute to the dissemination and progression of ovarian cancer. Our research group has shown that fluid shear stress (FSS) induces carboplatin resistance and a motile and aggressive phenotype in monolayer cultures and 3D models for adherent ovarian cancer. In this study, the effects of FSS on treatment response to cisplatin and doxorubicin were examined. The latter is used to manage recurrent platinum-resistant disease. Changes in mitochondrial function under FSS as they relate to platinum resistance were also characterized. Finally, the use of photodynamic therapy (PDT), which utilizes 690 nm light and a clinical photosensitizer benzoporphyrin derivative (BPD) to locally generate cytotoxic reactive molecular species as a means of overcoming FSS-induced platinum resistance, was explored. Methods: Human epithelial ovarian adenocarcinoma cells OVCAR-3 and Caov-3 (ATCC) were cultured in tissue culture plates (static culture) or chamber slides (ibidi) connected to a perfusion pump for 48 h (flow rate: 0.11 mL/min, shear stress: 0.41 dyn/cm2). Cells in static and flow cultures were exposed to cisplatin, doxorubicin, BPD-PDT or combinations thereof and survival fractions were measured 72 h post-treatment. Mitochondrial membrane potential was measured using JC-1 fluorescence assay, and mitochondrial DNA (mtDNA) copy number was quantified using qPCR. ATP content per cell was measured with a CellTiterGlo luminescence assay. Results: OVCAR-3 and Caov-3 cells grown under FSS developed significant resistance to cisplatin. Specifically, 3.13 µM cisplatin induced a 50% decrease in the survival fraction in OVCAR-3 static cultures but failed to decrease the survival fraction under flow. In contrast to these findings with platins, no resistance to doxorubicin was observed under flow. Evaluation of the mitochondrial function revealed increased ATP content and mtDNA copy number in flow cultures, suggesting that increased mitochondrial activity may contribute to platinum resistance. Finally, low-dose BPD-PDT (IC10, 0.15 J/cm2) enhanced the efficacy of cisplatin in OVCAR-3 cells under flow, indicating that PDT is a viable strategy to sensitize tumors exposed to FSS to platinum-based chemotherapy. Conclusions: Our data suggest that ovarian cancer cells that acquired resistance to platinum due to FSS remain sensitive to doxorubicin. Changes in mitochondrial function, including increased ATP content per cell and mtDNA copy number, have been identified as potential contributing factors to platinum resistance under FSS. Finally, low-dose BPD-PDT can be used to re-sensitize cells to cisplatin and overcome platinum resistance. Citation Format: Marta Overchuk, Brittany P. Rickard, Justin Tulino, Frances S. Ligler, Imran Rizvi. Mechanism-informed photochemical strategies to overcome fluid shear stress-induced platinum resistance in ovarian cancer [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 B111.

CircNUP50 is a novel therapeutic target that promotes cisplatin resistance in ovarian cancer by modulating p53 ubiquitination

BackgroundMost patients with ovarian cancer (OC) treated with platinum-based chemotherapy have a dismal prognosis owing to drug resistance. However, the regulatory mechanisms of circular RNA (circRNA) and p53 ubiquitination are unknown in platinum-resistant OC. We aimed to identify circRNAs associated with platinum-resistant OC to develop a novel treatment strategy.MethodsPlatinum-resistant circRNAs were screened through circRNA sequencing and validated using quantitative reverse-transcription PCR in OC cells and tissues. The characteristics of circNUP50 were analysed using Sanger sequencing, oligo (dT) primers, ribonuclease R and fluorescence in situ hybridisation assays. Functional experimental studies were performed in vitro and in vivo. The mechanism underlying circNUP50-mediated P53 ubiquitination was investigated through circRNA pull-down analysis and mass spectrometry, luciferase reporters, RNA binding protein immunoprecipitation, immunofluorescence assays, cycloheximide chase assays, and ubiquitination experiments. Finally, a platinum and si-circNUP50 co-delivery nanosystem (Psc@DPP) was constructed to treat platinum-resistant OC in an orthotopic animal model.ResultsWe found that circNUP50 contributes to platinum-resistant conditions in OC by promoting cell proliferation, affecting the cell cycle, and reducing apoptosis. The si-circNUP50 mRNA sequencing and circRNA pull-down analysis showed that circNUP50 mediates platinum resistance in OC by binding p53 and UBE2T, accelerating p53 ubiquitination. By contrast, miRNA sequencing and circRNA pull-down experiments indicated that circNUP50 could serve as a sponge for miR-197-3p, thereby upregulating G3BP1 to mediate p53 ubiquitination, promoting OC platinum resistance. Psc@DPP effectively overcame platinum resistance in an OC tumour model and provided a novel idea for treating platinum-resistant OC using si-circNUP50.ConclusionsThis study reveals a novel molecular mechanism by which circNUP50 mediates platinum resistance in OC by modulating p53 ubiquitination and provides new insights for developing effective therapeutic strategies for platinum resistance in OC.Graphical

PiR-1919609 Is an Ideal Potential Target for Reversing Platinum Resistance in Ovarian Cancer.

PIWI-interacting RNAs (piRNAs) are a type of noncoding small RNA that can interact with PIWI-like RNA-mediated gene silencing (PIWIL) proteins to affect biological processes such as transposon silencing through epigenetic effects. Recent studies have found that piRNAs are widely dysregulated in tumors and associated with tumor progression and a poor prognosis. Therefore, this study aimed to investigate the effect of piR-1919609 on the proliferation, apoptosis, and drug resistance of ovarian cancer cells. In this study, we used small RNA sequencing to screen and identify differentially expressed piRNAs in primary ovarian cancer, recurrent ovarian cancer, and normal ovaries. A large-scale verification study was performed to verify the expression of piR-1919609 in different types of ovarian tissue, including ovarian cancer tissue and normal ovaries, by RT-PCR and to analyze its association with the clinical prognosis of ovarian cancer. The expression of PIWILs in ovarian cancer was verified by RT-PCR, Western blotting and immunofluorescence. The effects of piR-1919609 on ovarian cancer cell proliferation, apoptosis and drug resistance were studied through in vitro and in vivo models. (1) piR-1919609 was highly expressed in platinum-resistant ovarian cancer tissues (p < 0.05), and this upregulation was significantly associated with a poor prognosis and a shorter recurrence time in ovarian cancer patients (p < 0.05). (2) PIWIL2 was strongly expressed in ovarian cancer tissues (p < 0.05). It was expressed both in the cytoplasm and nucleus of ovarian cancer cells. (3) Overexpression of piR-1919609 promoted ovarian cancer cell proliferation, inhibited apoptosis, and promoted tumor growth in nude mice. (4) Inhibition of piR-1919609 effectively reversed ovarian cancer drug resistance. In summary, we showed that piR-1919609 is involved in the regulation of drug resistance in ovarian cancer cells and might be an ideal potential target for reversing platinum resistance in ovarian cancer.

An Attention-Based Deep Learning Network for Predicting Platinum Resistance in Ovarian Cancer

An Attention-Based Deep Learning Network for Predicting Platinum Resistance in Ovarian Cancer

Activation of PI3K/AKT/mTOR signaling axis by UBE2S inhibits autophagy leading to cisplatin resistance in ovarian cancer

BackgroundEpithelial ovarian cancer (OC) is the fourth leading cause of cancer-related deaths in women, with a 5-year survival rate of 30%-50%. Platinum resistance is the chief culprit for the high recurrence and mortality rates. Several studies confirm that the metabolic regulation of ubiquitinating enzymes plays a vital role in platinum resistance in OC.MethodsIn this study, we selected ubiquitin-conjugating enzyme E2S (UBE2S) as the candidate gene for validation. The levels of UBE2S expression were investigated using TCGA, GTEx, UALCAN, and HPA databases. In addition, the correlation between UBE2S and platinum resistance in OC was analyzed using data from TCGA. Cisplatin-resistant OC cell lines were generated and UBE2S was knocked down; the transfection efficiency was verified. Subsequently, the effects of knockdown of UBE2S on the proliferation and migration of cisplatin-resistant OC cells were examined through the CCK8, Ki-67 immunofluorescence, clone formation, wound healing, and transwell assays. In addition, the UBE2S gene was also validated in vivo by xenograft models in nude mice. Finally, the relationship between the UBE2S gene and autophagy and the possible underlying regulatory mechanism was preliminarily investigated through MDC and GFP-LC3-B autophagy detection and western blotting experiments. Most importantly, experimental validation of mTOR agonist reversion (the rescuse experiments) was also performed.ResultsUBE2S was highly expressed in OC at both nucleic acid and protein levels. The results of immunohistochemistry showed that the level of UBE2S expression in platinum-resistant samples was significantly higher relative to the platinum-sensitive samples. By cell transfection experiments, knocking down of the UBE2S gene was found to inhibit the proliferation and migration of cisplatin-resistant OC cells. Moreover, the UBE2S gene could inhibit autophagy by activating the PI3K/AKT/mTOR signaling pathway to induce cisplatin resistance in OC in vivo and in vitro.ConclusionIn conclusion, we discovered a novel oncogene, UBE2S, which was associated with platinum response in OC, and examined its key role through bioinformatics and preliminary experiments. The findings may open up a new avenue for the evaluation and treatment of OC patients at high risk of cisplatin resistance.

1O CircIGF1R_0001 mediates platinum resistance in ovarian cancer that sensitive to PARP inhibitors via promoting PARP1 binding to DNA damage sites

1O CircIGF1R_0001 mediates platinum resistance in ovarian cancer that sensitive to PARP inhibitors via promoting PARP1 binding to DNA damage sites

Phase IIa Study of PLX2853 in Gynecologic Cancers With Known ARID1A Mutation and Phase Ib/IIa Study of PLX2853/Carboplatin in Platinum-Resistant Epithelial Ovarian Cancer.

The Bromodomain and Extra-Terminal (BET) domain proteins facilitate the development of many human cancers via epigenetic regulation. BET inhibitors may be effective in reversing platinum resistance in ovarian cancer (OC) and may generate synthetic lethality with ARID1A loss. PLX2853 is an orally active, small-molecule inhibitor of BET bromodomain-mediated interactions that exhibits low nanomolar potency in blocking all four BET family members. We conducted a multicenter and open-label study with two parallel arms: a phase IIa study of PLX2853 monotherapy in patients with advanced gynecologic malignancies with an ARID1A mutation and a phase Ib/IIa combination study of PLX2853 plus carboplatin in women with platinum-resistant OC. The primary objectives were safety and tolerability for phase Ib and efficacy for both phase IIa portions. Thirty-four of 37 enrolled patients completed at least one post-baseline response assessment. Of the 14 evaluable patients on the monotherapy arm, 1 (7.1%) achieved a best overall response of partial response (PR), 5 (35.7%) had stable disease (SD), and 8 (57.1%) had progressive disease (PD). Of the 20 evaluable patients on the combination arm, 1 (5.0%) had PR, 9 (45.0%) had SD, and 10 (50%) had PD. This study confirmed the safety profile of PLX2853 and demonstrated the feasibility of combination with carboplatin. Although these results did not meet the prespecified response criteria, evidence of clinical activity highlights the rationale for further exploration of BET inhibitors in patients with ARID1A-mutated gynecologic malignancies, possibly in combination with agents targeting potential feedback mechanisms such as the PI3K pathway.

AUF1-induced circular RNA hsa_circ_0010467 promotes platinum resistance of ovarian cancer through miR-637/LIF/STAT3 axis.

Increasing evidences has indicated that primary and acquired resistance of ovarian cancer (OC) to platinum is mediated by multiple molecular and cellular factors. Understanding these mechanisms could promote the therapeutic efficiency for patients with OC. Here, we screened the expression pattern of circRNAs in samples derived from platinum-resistant and platinum-sensitive OC patients using RNA-sequencing (RNA-seq). The expression of hsa_circ_0010467 was validated by Sanger sequencing, RT-qPCR, and fluorescence in situ hybridization (FISH) assays. Overexpression and knockdown experiments were performed to explore the function of hsa_circ_0010467. The effects of hsa_circ_0010467 on enhancing platinum treatment were validated in OC cells, mouse model and patient-derived organoid (PDO). RNA pull-down, RNA immunoprecipitation (RIP), and dual-luciferase reporter assays were performed to investigate the interaction between hsa_circ_0010467 and proteins. Increased expression of hsa_circ_0010467 is observed in platinum-resistant OC cells, tissues and serum exosomes, which is positively correlated with advanced tumor stage and poor prognosis of OC patients. Hsa_circ_0010467 is found to maintain the platinum resistance via inducing tumor cell stemness, and silencing hsa_circ_0010467 substantially increases the efficacy of platinum treatment on inhibiting OC cell proliferation. Further investigation reveals that hsa_circ_0010467 acts as a miR-637 sponge to mediate the repressive effect of miR-637 on leukemia inhibitory factor (LIF) and activates the LIF/STAT3 signaling pathway. We further discover that AUF1 could promote the biogenesis of hsa_circ_0010467 in OC. Our study uncovers the mechanism that hsa_circ_0010467 mediates the platinum resistance of OC through AUF1/hsa_circ_0010467/miR-637/LIF/STAT3 axis, and provides potential targets for the treatment of platinum-resistant OC patients.

Single-cell RNA-sequencing analysis reveals divergent transcriptome events between platinum-sensitive and platinum-resistant high-grade serous ovarian carcinoma.

Tumor resistance is one of the main reasons leading to the failure of ovarian cancer treatment. Overcoming platinum resistance remains the greatest challenge in the management of high-grade serous ovarian carcinoma (HGSC). Small conditional RNA-sequencing is a powerful method for exploring the complexity of the cellular components and their interactions in the tumor microenvironment. We profiled the transcriptomes of 35,042 cells from two platinum-sensitive and three platinum resistance HGSC clinical cases downloaded from Gene Expression Omnibus (GSE154600) and annotated tumor cells as platinum-resistant or sensitive based on the clinical trait. The study systematically investigated the inter-tumoral (using differential expression analysis, CellChat, and SCENIC) and intra-tumoral heterogeneity (using enrichment analysis such as gene set enrichment analysis, as well as gene set variation analysis, weighted gene correlation network analysis, and Pseudo-time analysis) of HGSC. A cellular map of HGSC generated by profiling 30,780 cells was revisualized using Uniform Manifold Approximation and Projection. The inter-tumoral heterogeneity was demonstrated with intercellular ligand-receptor interactions of major cell types and regulons networks. FN1, SPP1, and COLLAGEN play important roles in the cross-talk between tumor cells and the tumor microenvironment. HOXA7, HOXA9_extended, TBL1XR1_extended, KLF5, SOX17, and CTCFL regulons consistent with the distribution of platinum-resistant HGSC cells were the high activity regions. The intra-tumoral heterogeneity of HGSC was presented with corresponding functional pathway characteristics, tumor stemness features, and the cellular lineage transition from platinum-sensitive to resistant condition. Epithelial-mesenchymal transition played an important role in platinum resistance, whereas oxidative phosphorylation was the opposite. There was a small subset of cells in platinum-sensitive samples that had transcriptomic characteristics similar to platinum-resistant cells, suggesting that the progression of platinum resistance in ovarian cancer is inevitable. The present study describes a view of HGSC at single-cell resolution that reveals the characteristics of the HGSC heterogeneity and provides a useful framework for future investigation of platinum-resistant.

Abstract CT160: Phase 1b/2a clinical trial of the oral BET inhibitor PLX2853 as monotherapy for ARID1A mutated gynecologic cancers and in combination with carboplatin for platinum resistant ovarian cance

Abstract The Bromodomain and Extra-Terminal (BET) Domain proteins facilitate the development of many human cancers via epigenetic regulation. BET inhibitors may be effective in reversing platinum resistance in ovarian cancer (OC) and may generate synthetic lethality with ARID1A loss. PLX2853 is an orally active, small molecule inhibitor of BET bromodomain-mediated interactions that exhibits low nanomolar potency in blocking all 4 BET family members (BRD2, BRD3, BRD4, and BRDT). PLX2853 development is continuing at Opna Bio as OPN-2853. Clinical experience with PLX2853 monotherapy in subjects with heavily pretreated solid tumors and lymphoma showed signs of activity. The current study (NCT04493619) was designed as a multicenter, open-label trial with two parallel arms: (1) a phase 2a study of PLX2853 monotherapy in advanced gynecological malignancies with a known ARID1A mutation and (2) a phase Ib/2a combination study of PLX2853 plus carboplatin in platinum resistant OC. The primary objective of the Ib portion of the study was safety and tolerability, with the primary objective of both phase 2a portions being efficacy. In the monotherapy arm, up to 6 patients were treated at 80 mg PLX2853 daily in a safety lead-in, with progression to phase 2a using a Simon 2-stage design if dose limiting toxicities (DLTs) were observed in fewer than 33% subjects. In Stage 1, 6 additional subjects (N=12 total) were planned, with progression to stage 2 if two or more patients responded in stage 1. The combination arm included an escalation phase Ib. Three to six evaluable subjects were planned for each group, with dose escalation pending less than 33% DLT rate. The combination arm defined by the phase 1b portion of the study continued to a planned phase 2a Simon 2 stage design similar to that described for the monotherapy arm. 34 of 37 enrolled patients were evaluable with data from at least 1 post-baseline response (14 monotherapy, 20 combination therapy). Of the 14 evaluable patients on the monotherapy arm, 1 (7.1%) achieved a partial response (PR) with progression-free survival of 278 days, 5 (35.7%) had stable disease (SD) and 8 (57.1%) had progressive disease (PD). Of the 20 evaluable OC patients on the PLX2843 + carboplatin combination, 1 (5.0%) had PR, 9 (45.0%) had SD, and 10 (50%) had PD. This study in a larger cohort of gynecologic cancer patients confirmed the safety profile of the agent and demonstrated the feasibility of combination with carboplatin. While these results did not meet the pre-specified response criteria, evidence of clinical activity nevertheless highlights the rationale for further exploration of BRD4 inhibitors in patients with ARID1A-mutated gynecologic malignancies, possibly in combination with agents targeting potential feedback mechanisms such as the PI3K pathway, frequently activated in these cancers. Citation Format: Elizabeth M. Swisher, Linda R. Duska, Erika P. Hamilton, Amit M. Oza, Gini Fleming, Oladapo O. Yeku, Alexander I. Spira, Debra L. Richardson, Robin Guo, Jackie Walling, Kerry Inokuchi, Dmitriy Zamarin. Phase 1b/2a clinical trial of the oral BET inhibitor PLX2853 as monotherapy for ARID1A mutated gynecologic cancers and in combination with carboplatin for platinum resistant ovarian cance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT160.

ROS-mediated SRMS activation confers platinum resistance in ovarian cancer.

Ovarian cancer is the leading cause of death among gynecological malignancies. Checkpoint blockade immunotherapy has so far only shown modest efficacy in ovarian cancer and platinum-based chemotherapy remains the front-line treatment. Development of platinum resistance is one of the most important factors contributing to ovarian cancer recurrence and mortality. Through kinome-wide synthetic lethal RNAi screening combined with unbiased datamining of cell line platinum response in CCLE and GDSC databases, here we report that Src-Related Kinase Lacking C-Terminal Regulatory Tyrosine And N-Terminal Myristylation Sites (SRMS), a non-receptor tyrosine kinase, is a novel negative regulator of MKK4-JNK signaling under platinum treatment and plays an important role in dictating platinum efficacy in ovarian cancer. Suppressing SRMS specifically sensitizes p53-deficient ovarian cancer cells to platinum in vitro and in vivo. Mechanistically, SRMS serves as a "sensor" for platinum-induced ROS. Platinum treatment-induced ROS activates SRMS, which inhibits MKK4 kinase activity by directly phosphorylating MKK4 at Y269 and Y307, and consequently attenuates MKK4-JNK activation. Suppressing SRMS leads to enhanced MKK4-JNK-mediated apoptosis by inhibiting MCL1 transcription, thereby boosting platinum efficacy. Importantly, through a "drug repurposing" strategy, we uncovered that PLX4720, a small molecular selective inhibitor of B-RafV600E, is a novel SRMS inhibitor that can potently boost platinum efficacy in ovarian cancer in vitro and in vivo. Therefore, targeting SRMS with PLX4720 holds the promise to improve the efficacy of platinum-based chemotherapy and overcome chemoresistance in ovarian cancer.

Abstract 1679: Unraveling the function of TRAF2 and NCK interacting kinase (TNIK) in high-grade serous ovarian cancer

Abstract The large majority of high grade serous ovarian cancer (HGSOC) patients will eventually become resistant to platinum-based chemotherapy, highlighting the urgent need to develop novel therapeutics targeting recurrent, platinum-resistant disease. To study this, our lab generated two patient derived platinum-resistant tumor spheres from platinum-sensitive primary patient cells to better understand the biology behind recurrent disease and identify novel therapeutic targets. Utilizing an artificial intelligence (AI) powered model, we screened a library that consisted of compounds predicted to target known or postulated resistance mechanisms and involved a novel therapeutic target. From this screen, we identified a TNIK kinase inhibitor as the only compound to effectively kill HGSOC spheres while sparing non-malignant fallopian tube cells. TNIK plays a key role in Wnt pathway activation, which our lab has previously shown to be critical in driving cancer stemness and epithelial ovarian cancer platinum resistance. Additionally, patient data shows that TNIK is amplified in ovarian cancer more than any other cancer type and is highly activated in ovarian cancer patients. We found that this compound was able to decrease overall Wnt activity in our platinum-resistant cells and could resensitize our platinum-resistant cells to cisplatin. This work demonstrates the abilities of using AI to expedite the drug discovery process as well as uncover novel therapeutic targets which may lead to future therapeutic strategies for HGSOC patients who no longer respond to standard of care platinum chemotherapy. Citation Format: Noah Puleo, Michele Cusato, Dylan Carvette, Chantelle Husdon, Analisa DiFeo. Unraveling the function of TRAF2 and NCK interacting kinase (TNIK) in high-grade serous ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1679.

ACSL1-induced ferroptosis and platinum resistance in ovarian cancer by increasing FSP1 N-myristylation and stability

Reprogramming of lipid metabolism, which modulates energy utilization and cell signaling, maintains cell survival and promotes cancer metastasis in cancer cells. Ferroptosis is a type of cell necrosis caused by an overload of lipid oxidation, which has been demonstrated to be involved in cancer cell metastasis. However, the mechanism by which fatty acid metabolism regulates the anti-ferroptosis signaling pathways is not fully understood. The formation of ovarian cancer spheroids helps to counteract the hostile microenvironment of the peritoneal cavity with low oxygen, shortage of nutrients, and subjected to platinum therapy. Previously, we demonstrated that Acyl-CoA synthetase long-chain family member 1 (ACSL1) promotes cell survival and peritoneal metastases in ovarian cancer, but the mechanism is still not well elucidated. In this study, we demonstrate that the formation of spheroids and under exposure to platinum chemotherapy increased the levels of anti-ferroptosis proteins as well as ACSL1. Inhibition of ferroptosis can enhance spheroid formation and vice versa. Genetic manipulation of ACSL1 expression showed that ACSL1 reduced the level of lipid oxidation and increased the resistance to cell ferroptosis. Mechanistically, ACSL1 increased the N-myristoylation of ferroptosis suppressor 1 (FSP1), resulting in the inhibition of its degradation and translocation to the cell membrane. The increase in myristoylated FSP1 functionally counteracted oxidative stress-induced cell ferroptosis. Clinical data also suggested that ACSL1 protein was positively correlated with FSP1 and negatively correlated with the ferroptosis markers 4-HNE and PTGS2. In conclusion, this study demonstrated that ACSL1 enhances antioxidant capacity and increases ferroptosis resistance by modulating the myristoylation of FSP1.

Proteomic analysis reveals CAAP1 negatively correlates with platinum resistance in ovarian cancer

The present study sought to investigate the correlation between CAAP1 and platinum resistance in ovarian cancer and to preliminarily explore the potential biological function of CAAP1. Proteomic analysis was used to analyze differentially expressed proteins in platinum-sensitive and -resistant tissue samples of ovarian cancer. The Kaplan-Meier plotter was used for prognostic analysis. Immunohistochemistry assay and chi-square test were employed to explore the relationship between CAAP1 and platinum resistance in tissue samples. Lentivirus transfection, immunoprecipitation-mass spectrometry, and bioinformatics analysis were used to determine the potential biological function of CAAP1. Based on results, the expression level of CAAP1 was significantly higher in platinum-sensitive tissues compared to that in resistant tissues. Chi-square test demonstrated that there is a negative correlation between high expression of CAAP1 and platinum resistance. Overexpression of CAAP1 increased cis‑platinum sensitivity of the A2780/DDP cell line likely via the mRNA splicing pathway by interacting with the splicing factor AKAP17A. In summary, there is a negative correlation between high expression of CAAP1 and platinum resistance. CAAP1 might be a potential biomarker for platinum resistance in ovarian cancer. SignificancePlatinum resistance is a key factor affecting the survival of ovarian cancer patients. Understanding the mechanisms of platinum resistance is highly important for ovarian cancer management. Here, we performed the DIA- and DDA-based proteomics to analyze differentially expressed proteins in tissue and cell samples of ovarian cancer. We found that the protein identified as CAAP1, which was first reported to be involved in the regulation of apoptosis, may be negatively correlates with platinum resistance in ovarian cancer. In addition, we also found that CAAP1 enhanced the sensitivity of platinum-resistant cells to cis‑platinum via the mRNA splicing pathway by interacting with the splicing factor AKAP17A. Our data would be useful to reveal novel molecular mechanisms of platinum resistance in ovarian cancer.

Targeted PDT Combinations to Overcome Fluid Shear Stress-induced Platinum Resistance in Ovarian Cancer

Targeted PDT Combinations to Overcome Fluid Shear Stress-induced Platinum Resistance in Ovarian Cancer

Predicting Prognosis and Platinum Resistance in Ovarian Cancer: Role of Immunohistochemistry Biomarkers.

Ovarian cancer is a lethal reproductive tumour affecting women worldwide. The advancement in presentation and occurrence of chemoresistance are the key factors for poor survival among ovarian cancer women. Surgical debulking was the mainstay of systemic treatment for ovarian cancer, which was followed by a successful start to platinum-based chemotherapy. However, most women develop platinum resistance and relapse within six months of receiving first-line treatment. Thus, there is a great need to identify biomarkers to predict platinum resistance before enrolment into chemotherapy, which would facilitate individualized targeted therapy for these subgroups of patients to ensure better survival and an improved quality of life and overall outcome. Harnessing the immune response through immunotherapy approaches has changed the treatment way for patients with cancer. The immune outline has emerged as a beneficial tool for recognizing predictive and prognostic biomarkers clinically. Studying the tumour microenvironment (TME) of ovarian cancer tissue may provide awareness of actionable targets for enhancing chemotherapy outcomes and quality of life. This review analyses the relevance of immunohistochemistry biomarkers as prognostic biomarkers in predicting chemotherapy resistance and improving the quality of life in ovarian cancer.