Drug-resistant Epithelial Ovarian Cancer Research Articles

BBT-877, a Novel Autotaxin Inhibitor, Abrogates Drug Resistance in Epithelial Ovarian Cancer Stem Cells.

Cancer stem cells (CSCs) contribute significantly to the poor prognosis of patients with epithelial ovarian cancer (EOC) due to their roles in drug resistance and tumor metastasis. Autotaxin (ATX) plays a pivotal role in the maintenance of the CSC-like properties of EOC tumors. BBT-877 is a novel ATX inhibitor used in clinical treatment of idiopathic pulmonary fibrosis. However, the effects of BBT-877 on drug resistance and metastasis in ovarian CSCs remain unknown. In this study, we aimed to investigate the effects of BBT-877 on drug resistance and intraperitoneal metastasis of EOC. Spheroid-forming CSCs, which were isolated from two EOC cell lines, A2780 and SKOV3, were investigated by cell viability, western blot, PCR, Spheroid-forming assay, and in vivo experiments. Spheroid-forming CSCs exhibited increased CSC-like properties and paclitaxel (PTX) resistance. BBT-877 treatment inhibited the viability of spheroid-forming CSCs more potently than that of adherent ovarian cancer cell lines. Combinatorial treatment with BBT-877 and PTX significantly attenuated the viability of spheroid-forming CSCs. In a SKOV3 cells-derived intraperitoneal metastasis model, BBT-877 treatment reduced the number of metastatic tumor nodes, while combinatorial treatment with BBT-877 and PTX more potently attenuated the formation of metastatic nodes and accumulation of ascitic fluid. These results suggest that BBT-877 can be combined with conventional anticancer drugs for the treatment of patients with recurrent or drug-resistant EOC.

The anti-tumor effects of AZD4547 on ovarian cancer cells: differential responses based on c-Met and FGF19/FGFR4 expression

BackgroundThe FGF/FGFR signaling pathway plays a critical role in human cancers. We analyzed the anti-tumor effect of AZD4547, an inhibitor targeting the FGF/FGFR pathway, in epithelial ovarian cancer (EOC) and strategies on overcoming AZD4547 resistance.MethodsThe effect of AZD4547 on cell viability/migration was evaluated and in vivo experiments in intraperitoneal xenografts using EOC cells and a patient-derived xenograft (PDX) model were performed. The effect of the combination of AZD4547 with SU11274, a c-Met-specific inhibitor, FGF19-specific siRNA, or an FGFR4 inhibitor was evaluated by MTT assay.ResultsAZD4547 significantly decreased cell survival and migration in drug-sensitive EOC cells but not drug-resistant cells. AZD4547 significantly decreased tumor weight in xenograft models of drug-sensitive A2780 and SKOV3ip1 cells and in a PDX with drug sensitivity but not in models with drug-resistant A2780-CP20 and SKOV3-TR cells. Furthermore, c-Met expression was high in SKOV3-TR and HeyA8-MDR cells, and co-administration of SU11274 and AZD4547 synergistically induced cell death. In addition, expressions of FGF19 and FGFR4 were high in A2780-CP20 cells. Combining AZD4547 with FGF19 siRNA or with a selective FGFR4 inhibitor led to significantly reduced cell proliferation in A2780-CP20 cells.ConclusionsThis study showed that AZD4547 has significant anti-cancer effects in drug-sensitive cells and PDX models but not in drug-resistant EOC cells. In drug-resistant cells, the expression level of c-Met or FGF19/FGFR4 may be a predictive biomarker for AZD4547 treatment response, and a combination strategy of drugs targeting c-Met or FGF19/FGFR4 together with AZD4547 may be an effective therapeutic strategy for EOC.

Drug-Resistant Epithelial Ovarian Cancer: Current and Future Perspectives.

Epithelial ovarian cancer (EOC) is a complex disease with diverse histological subtypes, which, based on the aggressiveness and course of disease progression, have recently been broadly grouped into type I (low-grade serous, endometrioid, clear cell, and mucinous) and type II (high-grade serous, high-grade endometrioid, and undifferentiated carcinomas) categories. Despite substantial differences in pathogenesis, genetics, prognosis, and treatment response, clinical diagnosis and management of EOC remain similar across the subtypes. Debulking surgery combined with platinum-taxol-based chemotherapy serves as the initial treatment for High Grade Serous Ovarian Carcinoma (HGSOC), the most prevalent one, and for other subtypes, but most patients exhibit intrinsic or acquired resistance and recur in short duration. Targeted therapies, such as anti-angiogenics (e.g., bevacizumab) and PARP inhibitors (for BRCA-mutated cancers), offer some success, but therapy resistance, through various mechanisms, poses a significant challenge. This comprehensive chapter delves into emerging strategies to address these challenges, highlighting factors like aberrant miRNAs, metabolism, apoptosis evasion, cancer stem cells, and autophagy, which play pivotal roles in mediating resistance and disease relapse in EOC. Beyond standard treatments, the focus of this study extends to alternate targeted agents, including immunotherapies like checkpoint inhibitors, CAR T cells, and vaccines, as well as inhibitors targeting key oncogenic pathways in EOC. Additionally, this chapter covers disease classification, diagnosis, resistance pathways, standard treatments, and clinical data on various emerging approaches, and advocates for a nuanced and personalized approach tailored to individual subtypes and resistance mechanisms, aiming to enhance therapeutic outcomes across the spectrum of EOC subtypes.

Cholesterol Biosynthesis Inhibitor RO 48-8071 Suppresses Growth of Epithelial Ovarian Cancer Cells in Vitro and In Vivo.

Epithelial Ovarian Cancer (EOC) cells express enzymes in the cholesterol biosynthetic pathway, making this pathway an attractive therapeutic target for controlling ovarian cancer. Potent small molecule inhibitors of one biosynthetic enzyme, Oxidosqualene Cyclase (OSC), have been identified, and RO 48-8071 (4'-[6-(allylmethylamino)hexyloxy]-4-bromo-2'-fluorobenzophenone fumarate) (RO), has emerged as a useful chemotherapeutic agent for breast and prostate cancer. Cell viability assays were performed to determine effects of RO 48-8071 on growth of EOC cells. Aldehyde Dehydrogenase (ALDH) assay was conducted to determine the effects of drug on reducing stem cell like properties of EOC cells. Finally, xenograft studies were performed to assess the ability of RO 48-8071 to inhibit the growth of EOC cells in vivo. We found that short-term (24-48 h) administration of pharmacological doses of RO effectively reduced the viability of drug-resistant EOC cells (SK-OV-3 and OVCAR-3), as determined with sulforhodamine B colorimetric assays. In 7-day assays, nanomolar concentrations of RO effectively inhibited the growth of EOC cells. RO also suppressed ALDH activity, a marker of stem cells. Importantly, RO significantly suppressed growth of xenografts derived from EOC cells when given to mice intraperitoneally (20-40 mg kg-1 day-1) for 27 days once tumors reached 100 mm3 (controls: 336 + 60 mm3; treated: 171 + 20 mm3) with no toxicity to the experimental animals. Mechanistically, RO induced apoptosis in tumor cells in vivo as shown with immunohistochemistry. Cholesterol biosynthesis inhibitor RO 48-8071 is thus a novel and potent inhibitor of human EOC, including EOC stem cells.

TAZ Regulates the Cisplatin Resistance of Epithelial Ovarian Cancer Cells via the ANGPTL4/SOX2 Axis.

Objective Epithelial ovarian cancer (EOC) is a fatal gynecological malignancy. This study explored the mechanism of TAZ in regulating drug sensitivity of cisplatin (DDP-)-resistant EOC cells through the ANGPTL4/SOX2 axis. Methods The A2780/DDP cells were prepared by stepwise progressive concentration method. The drug resistance and TAZ expression in EOC cells were determined. Drug sensitivity was measured after TAZ overexpression in A2780 cells and TAZ downregulation in A2780/DDP cells, respectively. The effects of TAZ knockdown on apoptosis rate, stemness, and cancer stem cell (CSC) marker (CD44, OCT4, and ALDH1A) levels in A2780/DDP and DDP-treated A2780/DDP cells were assessed. The binding of TAZ and ANGPTL4 was verified using ChIP-qPCR, and ANGPTL4 and SOX2 levels were determined. The effects of different combined treatments of TAZ, ANGPTL4, and SOX2 on drug sensitivity of A2780/DDP cells and DDP-treated A2780/DDP cells were evaluated. Results TAZ was upregulated in drug-resistant EOC cells. TAZ knockdown significantly increased the drug sensitivity of A2780/DDP cells, while TAZ overexpression markedly decreased the drug sensitivity of A2780 cells. TAZ silencing promoted apoptosis of drug-resistant EOC cells and inhibited cell stemness. TAZ targeted ANGPTL4 and TAZ silencing enhanced drug sensitivity of A2780/DDP cells by inhibiting ANGPTL4. ANGPTL4 overexpression elevated SOX2 expression, and SOX2 downregulation reduced the drug resistance and promoted the apoptosis of A2780/DDP cells. Conclusion TAZ regulates DDP sensitivity of drug-resistant EOC cells via the ANGPTL4/SOX2 axis.

Application of Arsenic Trioxide-Based Combined Sequential Chemotherapy in Recurrent Resistant and Refractory Ovarian Cancers: A Single-Center, Open Phase II Clinical Study.

Objective Arsenic trioxide (ATO) has been effectively used for the treatment of hematological malignancies and some solid tumors, while ATO effects were not tested clinically in epithelial ovarian cancer (EOC). Methods Patients with primary or secondary platinum-resistant EOC were enrolled from October 2015 to December 2019. Patients were mainly treated with ATO-based combined sequential chemotherapy as follows: Regimen 1 (ATO combined taxanes weekly therapy); Regimen 2 (ATO + taxanes + 5-fluorouracil + adriamycin ± bevacizumab sequential chemotherapy), for 5 patients platinum-free interval >12 months, added oxaliplatin). Prespecified end points in this cohort included confirmed best overall response rate (ORR), disease control rate (DCR), progression-free survival (PFS), overall survival (OS), and safety. Results A total of 33 patients were enrolled in this study. After a median follow-up time of 22.1 months (range 5.5–42.9 months), ORR was 42% and DCR was 85%. The overall PFS was 9.5 months (range 1–38.4 months). The main side effect was myelosuppression. Conclusions ATO-based sequential combined chemotherapy is effective for primary and recurrent drug-resistant EOC patients in clinical phase II trials. The associated side effects could be controlled, while further study is needed.

Bioinformatics analysis of drug-resistant ceRNA in epithelial ovarian cancer

Objective: To explore the possible biological function of long-chain non-coding RNA (lncRNA) on epithelial ovarian cancer (EOC) drug resistance and the value of new diagnostic markers through bioinformatics analysis, clinical testing and verification methods. Methods: (1) Mining the lncRNA related to EOC and constructing the competing endogenous RNA (ceRNA) regulatory network: comprehensively apply text mining, data prediction and network construction and other bioinformatics methods to establish a potential ceRNA regulatory network related to EOC drug resistance, namely lncRNA-microRNA (miRNA)-mRNA regulatory network. (2) Clinical verification: a total of 95 cancer tissue specimens were collected from EOC patients who underwent cytoreductive surgery at the Affiliated Tumor Hospital of Guangxi Medical University from June 2008 to October 2016, of which 54 were platinum-resistant patients (resistance group), 41 platinum-based drug-sensitive patients (sensitive group). Real-time fluorescent quantitative PCR was used to detect the expression of lncRNA in EOC tissues of the two groups, the effect of lncRNA expression on the prognosis of EOC patients, and the diagnostic efficacy of lncRNA expression on resistance to EOC were also analyzed. Results: (1) Text mining preliminarily screened out 25 differentially expressed lncRNA related to the occurrence and development of EOC, and further subcellular localization analysis found that 8 lncRNA exist in the cytoplasm. Through further data mining, collinear literature analysis and construction of ceRNA, the regulatory network predicts that the two lncRNA molecules, GAS5 and HOTAIR, could serve as key ceRNA molecules. (2) Through real-time fluoressent quantitative PCR verification, it was found that both GAS5 and HOTAIR were highly expressed in drug-resistant EOC tissues, which affects the progression-free survival (PFS) and overall survival (OS) time of patients with drug-resistant EOC independent risk factors (P<0.05). The receiver operating characteristic (ROC) area under the curve (AUC) of GAS5 alone was 0.678, the AUC of HOTAIR alone was 0.863, and the AUC of GAS5 combined with HOTAIR was 0.871, and there were statistically significant differences (all P<0.05). Conclusions: The high expression of GAS5 and HOTAIR is closely related to the drug resistance of EOC, which could be used as a potential predictor of response to chemotherapy. At the same time, the combined detection of GAS5 and HOTAIR has a certain diagnostic efficiency for patients with platinum-resistant EOC. This method of using the ceRNA regulatory network to predict key molecules will provide new ideas for the diagnosis and treatment of EOC.

Chloroquine reverses chemoresistance via upregulation of p21WAF1/CIP1 and autophagy inhibition in ovarian cancer

Overcoming drug-resistance is a big challenge to improve the survival of patients with epithelial ovarian cancer (EOC). In this study, we investigated the effect of chloroquine (CQ) and its combination with cisplatin (CDDP) in drug-resistant EOC cells. We used the three EOC cell lines CDDP-resistant A2780-CP20, RMG-1 cells, and CDDP-sensitive A2780 cells. The CQ-CDDP combination significantly decreased cell proliferation and increased apoptosis in all cell lines. The combination induced expression of γH2AX, a DNA damage marker protein, and induced G2/M cell cycle arrest. Although the CQ-CDDP combination decreased protein expression of ATM and ATR, phosphorylation of ATM was increased and expression of p21WAF1/CIP1 was also increased in CQ-CDDP-treated cells. Knockdown of p21WAF1/CIP1 by shRNA reduced the expression of γH2AX and phosphorylated ATM and inhibited caspase-3 activity but induced ATM protein expression. Knockdown of p21WAF1/CIP1 partly inhibited CQ-CDDP-induced G2/M arrest, demonstrating that knockdown of p21WAF1/CIP1 overcame the cytotoxic effect of the CQ-CDDP combination. Ectopic expression of p21WAF1/CIP1 in CDDP-treated ATG5-shRNA/A2780-CP20 cells increased expression of γH2AX and caspase-3 activity, demonstrating increased DNA damage and cell death. The inhibition of autophagy by ATG5-shRNA demonstrated similar results upon CDDP treatment, except p21WAF1/CIP1 expression. In an in vivo efficacy study, the CQ-CDDP combination significantly decreased tumor weight and increased expression of γH2AX and p21WAF1/CIP1 in A2780-CP20 orthotopic xenografts and a drug-resistant patient-derived xenograft model of EOC compared with controls. These results demonstrated that CQ increases cytotoxicity in combination with CDDP by inducing lethal DNA damage by induction of p21WAF1/CIP1 expression and autophagy inhibition in CDDP-resistant EOC.

Lentivirus-Mediated RNAi silencing targeting ERCC1 reverses cisplatin resistance in cisplatin-resistant ovarian carcinoma cell line.

The aim of the study was to investigate the potential mechanisms that interferencing of excision repair cross-complementing gene 1 (ERCC1) mediated by lentiviral vector in cisplatin-resistant ovarian cancer SKOV3/DDP cells. The human platinum-resistant ovarian carcinoma cell line SKOV3/DDP was transfected by pLVX-shRNA lentivirus. Interference efficiency for ERCC1 by lentiviruses transfection was detected by real-time polymerase chain reaction and western blot assay. CCK-8 assay was used for cell proliferation on cell resistance after transfection with ERCC1. Effects of cell apoptosis and cell cycles were detected by flow cytometry. The expression levels of ERCC1 were significantly suppressed in SKOV3/DDP cells after stably transfecting with shERCC1-recombinant plasmid. The results of cell viability assay demonstrated that interference with ERCC1 gene increased the sensitivity of SKOV3/DDP cells to cisplatin (p<0.01). ERCC1 gene-specific silencing promoted cell apoptosis of SKOV3/DDP cells (p<0.01) detected by flow cytometry. Cell cycle analysis results showed that the proportion of cells in G1 and S phase decreased, while the proportion of G2 phase cells increased in ERCC1-silencing cells. The differences were statistically significant (p<0.01), which demonstrated that stable interferencing with ERCC1 induced the cells arrest in G2 phase after being treated by DDP and silencing the expression of ERCC1 inhibited cell proliferation by preventing the progression of cell mitosis. ERCC1 gene silencing effectively reversed SKOV3/DDP cell resistance to cisplatin and increased sensitivity to cisplatin resistance in cisplatin-resistant ovarian cancer cells. Interference of ERCC1 promoted the apoptosis of SKOV3/DDP cells and prevented cell mitosis by inducing G0/G1 phase arrest. Thus, ERCC1 could be a potential therapeutic target for the therapy of cisplatin-resistant ovarian cancer and it would provide new ideas for epigenetic therapy of drug-resistant epithelial ovarian cancer.

Oxaliplatin-based combination chemotherapy is still effective for the treatment of recurrent and platinum-resistant epithelial ovarian cancer: results from a single center

Background Combination paclitaxel and carboplatin is currently a first-line regimen for ovarian cancer. However, many patients develop tumor recurrence or drug resistance to this regimen. The study aims to investigate the effectiveness and safety of an oxaliplatin + epirubicin + ifosfamide regimen for the treatment of recurrent and drug-resistant epithelial ovarian cancer. Methods A retrospective analysis of 73 patients with recurrent and drug-resistant ovarian cancer was performed; 38 cases of them received oxaliplatin + epirubicin + ifosfamide regimens (IAP group), 35 patients received non-oxaliplatinbased chemotherapy regimens (control group). The therapeutic effects and side effects of the oxaliplatin + epirubicin + ifosfamide regimen were analyzed and summarized. Kaplan-Meier survival curves and Cox proportional hazards regression were used to compare progression-free and overall survival between the two groups. Results Of the 38 patients in the IAP group, 14 patients (36.84%) achieved complete remission, 12 (31.58%) achieved partial remission, 2 (5.26%) achieved stable disease and 10 (26.32%) developed progressive disease. The overall effective rate (complete or partial remission) of the IAP regime was 68.42%. While, of the 35 patients in the control group, 12 patients (34.29%) achieved complete remission, 3 (8.57%) achieved partial remission, 5 (14.29%) achieved stable disease and 15 (42.86%) developed progressive disease. The overall effective rate was 42.86%, which was lower than that in the IAP group (P=0.035, χ2=4.836). Progression-free survival was 9.5 months (0–64 months) in the IAP group vs. 3 months (0–74 months) in the non-oxaliplatin group (P=0.014 by Kaplan-Meier survival curves; HR=2.260; 95%CI 1.117–4.573; P=0.023 by Cox proportional hazards regression). Median overall survival was 46 months (9–124 months) in the IAP group vs. 35 months (9–108 months) in non-oxaliplatin group (P=0.018 by Kaplan-Meier survival curves; HR=2.272; 95% CI 1.123–4.598; P=0.022 by Cox proportional hazards regression). In IAP group, 15.79% (6/38) of the patients suffered grade III-IV bone marrow arrest. The main non-hematological side effects of the IAP regimen included nausea and vomiting (21.05%, 8/38), peripheral neurotoxicity (15.79%, 6/38) and hepatic or renal lesions (2.63%, 1/38). The main side effects of the two chemotherapy regimens showed no statistical difference. Conclusion The oxaliplatin-based IAP regimen is potentially effective for salvage chemotherapy in patients with recurrent and drug-resistant ovarian cancer, with a better therapeutic effect and tolerable side effects.

Abstract IA17: Targeting the methylome for epigenetic resensitization of ovarian cancer

Abstract Women with advanced stage ovarian cancer (OC) have a five-year survival rate of less than 25%. Although most patients respond to platinum-based chemotherapy, relapses are common, leading to platinum-resistant OC, which is uniformly fatal. OC progression is associated with accumulation of epigenetic alterations. In particular, deoxycytosine methylation of CpG islands in promoter regions of tumor suppressor genes (TSGs) plays a prominent role in the development and progression of drug-resistant epithelial OC. We recently demonstrated for the first time in a clinical trial that therapeutic interventions targeting the OC methylome reverse drug resistance and induce meaningful clinical responses. We showed that repetitive low-dose decitabine reactivated silenced genes and restored sensitivity to carboplatin, providing strong clinical and biological support for further study of hypomethylating agents in heavily pre-treated, platinum-resistant ovarian cancer patients. While the FDA-approved demethylating agent decitabine is prone to deamination by cytidine deaminase, SGI-110 (Astex Pharmaceuticals, Inc.), a dinucleotide analogue of decitabine, is more stable, less toxic, and a promising alternative to restoring silenced TSG expression in cancer cells by reversal of DNA methylation. Our preclinical evaluation demonstrated that SGI-110 resensitized platinum-resistant OC cell lines to cisplatin (CDDP) (3-fold reduction in IC50) and reduced the CDDP IC50. SGI-110 treatment induced significant demethylation and subsequent transcriptional derepression of tumor suppressors and differentiation-associated genes in OC cells. SGI-110 alone or in combination with CDDP was well tolerated in non-tumor bearing mice. Significant antitumor activity was observed in mice harboring subcutaneous OC tumors and treated with single SGI-110 and SGI-110 + CDDP treatment in both a biweekly and daily (QD5) regimen. In addition to reducing tumor growth in xenografts, SGI therapy was effective in causing global as well as TSG demethylation and gene reexpression in vivo. Furthermore, the antitumor activity of SGI-110 was associated with reduced chromatin compaction, allowing greater CDDP intercalation into DNA, as assessed by increased DNA platinum adducts in SGI-treated OC cells. The results of our preclinical study support our recently activated clinical trial NCT01696032 using SGI-110 in combination with carboplatin in patients with recurrent, platinum-resistant OC. Clinical specimens (tumor and plasma samples) will be analyzed for epigenetic biomarker changes. We seek to bring forward the new concept of epigenetic targeting in platinum resistant OC by priming the tumors with SGI-110 and set the stage for interventions targeting the OC epigenome, as well as guide and impact the design of future clinical investigations in OC. Citation Format: Kenneth P. Nephew, Daniela Matei, Pietro Taverna, Fang Fang, Jessica Tang, Gavin Choy, John Lyons, Mohammad Azab, Jay Pilrose, John Turchi. Targeting the methylome for epigenetic resensitization of ovarian cancer. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: From Concept to Clinic; Sep 18-21, 2013; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2013;19(19 Suppl):Abstract nr IA17.

Abstract 4081: In vivo effects of decitabine on global gene expression profiles in tumors from patients with platinum-resistant ovarian cancer

Abstract Deoxycytosine methylation of CpG islands within promoter regions of tumor suppressor genes (TSGs) plays a prominent role in the development and progression of drug-resistant epithelial ovarian cancer (OC). Recently, in a phase I/II trial of the DNA methylation inhibitor decitabine in combination with carboplatin in platinum-resistant OC patients (NCT00477386), we demonstrated that decitabine-altered DNA methylation resulted in platinum resensitization and significant clinical activity, with a response rate of 35% and median PFS of 10 months (ASCO abstract #79158). The objective of the current study was to investigate the molecular basis underlying the clinical response observed. For this, we compared differential gene expression in paired tumor biopsies and ascitic fluid collected before and one week after decitabine treatment. Of the 17 patients enrolled in NCT00477386, samples evaluable from 14 patients were subjected to global gene expression profiling using GeneChip Human Gene 1.0 St arrays, and selected genes were validated by quantitative RT-PCR. Data analysis was performed using significance of microarray analysis (SAM), clustering, functional pathway prediction using DAVID, gene ontology (GO), and gene set enrichment analysis (GSEA). In the patients with progression free survival (PFS) greater than six months (n=6), 274 genes were uniquely upregulated by decitabine. Enriched signaling pathways included Hedgehog, focal adhesion, and gap junction. Specifically, genes upregulated (fold change &amp;gt;1.2, P &amp;lt; 0.05) in the Hedgehog pathway included PTCH2 (a putative TSG), the hedgehog antagonist HHIP, and BAALC (with the latter two genes frequently silenced by DNA methylation in cancer), and MMP8 (associated with decreased lung cancer risk). Expression of AKT1 was higher in patients with PFS &amp;gt; 6 months compared to patients with PFS &amp;lt; 6 months (fold change 1.9 vs. 1.2 compared to baseline). MLH1 (mismatch repair gene) expression was increased (1.3 fold-change compared to baseline) in patients with PFS &amp;gt; 6 months and decreased in patients with PFS &amp;lt; 6 months (-1.2 fold-change). Furthermore, 394 genes were downregulated (FC &amp;lt; –1.2, P &amp;lt; 0.05) by decitabine in patients with PFS &amp;gt; 6 months, including 33 genes of the “stemness” and chemoresistance-associated Wnt pathway. Notably, underexpression of those 33 genes has been correlated with prolonged survival in previous ovarian cancer studies. In summary, these findings show that repetitive low-dose decitabine reactivates silenced genes and restores sensitivity to carboplatin, providing strong clinical and biological support for further study of hypomethylating agents in heavily pre-treated, platinum-resistant ovarian cancer patients. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4081. doi:1538-7445.AM2012-4081

Abstract 4077: Chemosensitizing effects of the novel, small molecule DNA methylation inhibitor SGI-110 in ovarian cancer

Abstract Deoxycytosine methylation of CpG islands in promoter regions of tumor suppressor genes (TSGs) plays a prominent role in the development and progression of drug-resistant epithelial ovarian cancer (OC). We previously demonstrated in a phase I/II trial that the DNA methylation inhibitor decitabine alters DNA methylation and restores platinum sensitivity in platinum-resistant OC patients, resulting in significant clinical activity. SGI-110 (Astex Pharmaceuticals) is a DNA hypomethylating agent with demonstrated activity in restoring silenced TSG expression in cancer cells by reversal of DNA methylation. As a decitabine-deoxyguanosine dinucleotide, SGI-110 has been shown to be less prone to deamination by cytidine deaminase and could have advantages over decitabine, such as better stability, less toxicity and a more convenient and less frequent SQ administration. We examined SGI-110 for its ability to inhibit OC cell proliferation and to demethylate and induce TSGs in vitro and in vivo. A 48 hour pretreatment with SGI-110 resensitized drug-resistant ovarian cancer cell lines to cisplatin (3-fold reduction in IC50 of cisplatin). In A2780 platinum sensitive OC cells, SGI-110 pre-treatment for 5 days reduced cisplatin IC50 by &amp;gt;2-fold. Prolonged (7 days) SGI-110 treatment reduced by 2-fold the number of ALDH1+ cells in SKOV3 and A2780 cells, suggesting an effect on the stem cell population, potentially involved in drug resistance. SGI-110 induced significant demethylation of TSGs ras-associated domain family 1A (RASSF1A) and human MutL homologue-1 (MLH1) and the differentiation-associated gene HOXA10; furthermore, RASSF1A, MLH1 and HOXA10 gene reexpression was also observed after 48 hour SGI-110 treatment. SGI-110 prevented TGF-β induced epithelial to mesenchymal transition of OC cells, as measured morphologically and by quantification of E-cadherin, Zeb1, Slug and miR200c expression levels. SGI-110 suppressed E-cadherin promoter methylation induced by TGF-β. We then examined the in vivo tolerability and efficacy of SGI-110, singly and in combination with cisplatin, in nude athymic mice. Mice were injected qd or bi-weekly with SGI-110 (sc) and/or cisplatin (ip) and body weights were measured twice weekly. In the qd regimen, SGI-110 2 mg/kg plus 4 mg/kg cisplatin was tolerated. The 10 mg/kg bi-weekly dose of SGI-110 was tolerated, either alone or in combination with 2 mg/kg cisplatin (5mg/kg SGI-110 plus 4 mg/kg cisplatin was similarly tolerated). SGI-110 induced significant global hypomethylation, as determined by pyrosequencing analysis of LINE1 demethylation in peripheral blood mononuclear cells. We are currently assessing the activity of SGI-110 in combination with cisplatin to retard the growth of platinum resistant human ovarian cancer xenografts. In summary, SGI-110 combined with platinum is a promising clinical combination for the therapy of ovarian cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4077. doi:1538-7445.AM2012-4077

Transfection of Smac/DIABLO sensitizes drug-resistant tumor cells to TRAIL or paclitaxel-induced apoptosis in vitro

Smac/DIABLO is a recently identified protein released from mitochondria in response to apoptotic stimuli and promotes apoptosis by antagonizing inhibitor of apoptosis proteins (IAPs). In this study, we observed depressed Smac/DIABLO and increased XIAP expression in ovarian epithelial tissues ordered by normal, benign and malignant epithelia. In epithelial ovarian cancer (EOC), the expression of Smac/DIABLO decreased with the malignancy. Smac/DIABLO expression showed no correlation with TRAIL sensitivity, while lower Smac/DIABLO expression and decreased release of Smac/DIABLO from mitochondria upon apoptosis stimuli were observed in paclitaxel-resistant A2780/pac cells as compared to the sensitive controls. Ectopic Smac/DIABLO alone inhibited cell growth, arrested cells in G0/G1 phase, and sensitized drug-resistant EOC cells to TRAIL or paclitaxel-induced apoptosis. Increased apoptosis was associated with the down-regulation of XIAP, FLIP, and up-regulation of Smac/DIABLO, cytochrome c, p53, along with increased activity of caspase-3. Thus, over-expression of Smac/DIABLO is a promising strategy for drug-resistant ovarian cancer treatment.