HDAC6-selective inhibitors enhance anticancer effects of paclitaxel in ovarian cancer cells

Histone deacetylase 6 (HDAC6)-selective inhibitors are potent anticancer agents that are gaining increasing attention and undergoing various developments. These have been approved or are under clinical trials for use with other anticancer agents, such as pomalidomide, anti-programmed death-ligand 1 antibody and paclitaxel, for various types of cancer, including solid tumors. In the present study, a second generation HDAC6-selective inhibitor, ACY-241 (citarinostat), and a novel inhibitor, A452, exhibited synergistic anticancer effects with paclitaxel in AT-rich interaction domain 1A-mutated ovarian cancer in vitro. Co-treatment of paclitaxel and the two HDAC6 inhibitors synergistically decreased cell growth and viability of TOV-21G. Furthermore, the protein expression levels of pro-apoptotic markers, such as poly(ADP-ribose) polymerase, cleaved caspase-3, Bak and Bax, were increased, whereas the expression levels of anti-apoptotic markers, such as Bcl-xL and Bcl-2, were decreased synergistically. Treatment with all drug combinations increased the portion of apoptotic cells in fluorescence-activated cell sorting analysis. These results demonstrated synergy between paclitaxel and HDAC6-selective inhibitors, providing further impetus for clinical trials of combination therapy using HDAC6-selective inhibitors, not only in ovarian cancer but also in other tumors.     

Curcumin enhances the anticancer effects of trichostatin a in breast cancer cells

Breast cancer patients with HER‐2 positive or estrogen receptor negative tumors have a poor prognosis because these tumors are aggressive and respond poorly to standard therapies. Histone deacetylase (HDAC) inhibitors have been shown to decreased cell survival, which suggests that HDAC inhibitors may be developed for preventing and treating breast cancer. Curcumin has anti‐inflammatory and proapoptotic effects in cancer cells. We determined whether the HDAC inhibitor, Tricostatin A (TSA) in combination with curcumin would produce greater antiproliferative and apoptotic effects than either agent alone. Increasing the concentration of curcumin from 10 to 20 µM enhanced the growth inhibitory effects of the combination in SkBr3 and 435eB breast cancer cells, which was accompanied by decreased viability along with decreased phosphorylation of ERK and Akt. The decreased cell viability observed in SkBr3 cells when curcumin was combined with TSA led to a G0/G1 cell cycle arrest and increased p21 and p27, and decreased Cyclin D1 protein expression. The combination induced cleavage of caspase 3 and poly(ADP‐ribose) polymerase‐1, suggesting that cell death occurred by apoptosis. There were no changes in protein expression of Bcl2, Bax, or Bcl‐xL and decreased expression of p53. The combination increased protein expression of phosphorylated JNK and phosphorylated p38. Pharmacological inhibition of JNK, but not p38, attenuated the decreased viability induced by the curcumin and TSA combination. We conclude that p53 independent apoptosis induced by combining curcumin and TSA involves JNK activation. These findings provide a rationale for exploring the potential benefits of the combination of curcumin with TSA for treatment of breast cancer. © 2012 Wiley Periodicals, Inc.     

Novel inhibitors of urokinase-type plasminogen activator and matrix metalloproteinase expression in metastatic cancer cell lines

The plasminogen-activating (PA) and matrix metalloproteinase (MMP) enzyme systems are implicated in proteolytic turnover of the extracellular matrix (ECM) associated with biologic processes including wound healing, inflammation and angiogenesis. Aberrant expression of components of the PA and MMP enzyme systems occurs in the pathogenesis of metastatic cancer. Oxamflatin (Ox), a novel hydroxamic acid derivative, inhibits u-PA mRNA expression and proteolytic activity while simultaneously upregulating the expression of the natural inhibitor of u-PA, plasminogen activator inhibitor type 2 (PAI-2) in metastatic cancer cells. We have characterized the effects of Ox and a novel derivative, Metacept-1 (MCT-1), on PA and MMP-mediated proteolysis and invasion in several metastatic tumor lines. Both compounds are able to inhibit u-PA-, MMP-2- and MMP-9-mediated gene expression at low micromolar concentrations as well as u-PA- and MMP-mediated proteolysis as assessed by zymography, with MCT-1 being the more effective of the 2 agents in some assays. Cellular invasion assays correlate with gene expression and zymography experiments identifying both Ox and MCT-1 as able to inhibit invasion of metastatic cancer cell lines through matrigel at nanomolar concentrations, with MCT-1 more effective than Ox in 2 of the 3 cancer cell lines assessed.     

Dub3 controls DNA damage signalling by direct deubiquitination of H2AX

A crucial event in the DNA damage response is the phosphorylation and subsequent ubiquitination of H2AX, required for the recruitment of proteins involved in DNA repair. Here we identify a novel regulator of this process, the ubiquitin hydrolase Dub3. Overexpression of wild type, but not catalytic inactive, Dub3 decreases the DNA damage‐induced mono‐ubiquitination of H2A(X) whereas downregulation of Dub3 has the opposite effect. Dub3 overexpression abrogates focus formation of 53BP1 and BRCA1 in response to genotoxic stress. However, focus formation of MDC1 and γH2AX, earlier events in this response, are unaffected by Dub3 overexpression. We show that Dub3 counteracts H2AX E3 ligases RNF8 and RNF168. Moreover, Dub3 and H2AX interact and Dub3 deubiquitinates H2AX in vitro. Importantly, overexpression of Dub3 delays H2AX dephosphorylation and recovery of MDC1 focus formation at later time points after DNA damage, whereas H2AX dephosphorylation at later time points is faster after Dub3 depletion. Altogether these results show that Dub3 regulates a correct DNA damage response by controlling H2AX ubiquitination.     

Sensitization of ovarian carcinoma cells to the atypical retinoid ST1926 by the histone deacetylase inhibitor,RC307: enhanced DNA damage response

The synthetic atypical retinoids containing an adamantyl group exhibit antiproliferative or proapoptotic activities. Apoptosis induction is a dose‐dependent effect independent of retinoid receptors. We have reported that induction of apoptosis by the atypical retinoid, ST1926, is associated with early manifestations of genotoxic stress. Indeed, in this study performed in ovarian carcinoma cells, we show that exposure to ST1926 resulted in an increase of early markers of DNA damage, including ATM and H2AX phosphorylation. In addition, we found that a novel histone deacetylase (HDAC) inhibitor (RC307) was able to enhance sensitivity of ovarian carcinoma cells to ST1926. Under conditions where single‐agent treatment caused only antiproliferative effects, the combination of the atypical retinoid and HDAC inhibitor resulted in marked apoptotic cell death with a more rapid onset in wild‐type p53 ovarian carcinoma cells. The sensitization to ST1926‐induced apoptosis was associated with an enhanced DNA damage response, because a prolonged expression of DNA damage markers (e.g., H2AX, p53 and RPA‐2 phosphorylation) and a marked activation of DNA damage checkpoint kinases (in particular, phosphorylation of Chk1) were observed indicating an accumulation of DNA damage by the ST1926/HDAC inhibitor combination. The study provides additional support to the role of DNA damage as a primary event leading to the activation of apoptosis in ovarian carcinoma cells by adamantyl retinoids and documents the potential therapeutic efficacy of the combination of ST1926 and HDAC inhibitors of the novel series.     

miR-515-5p通过靶向HDAC2影响食管癌发生发展的分子机制

目的：探讨miR-515-5p对食管癌细胞增殖、迁移和侵袭的影响及其分子机制。方法：选取2020年6月至2020年12月在河北医科大学第四医院手术切除的60例食管癌患者的癌组织标本和20例健康成人的食管上皮组织标本,以及食管癌细胞TE1、Eca109、KYSE30和KYSE170,用q PCR法检测食管癌组织和细胞中miR-515-5p的表达水平。在Eca109细胞中转染miR-515-5p模拟物以及其阴性对照物、在TE1细胞中转染miR-515-5p抑制剂以及其阴性对照物,q PCR法检测转染效率,用CCK-8法、Transwell实验分别检测转染细胞的增殖、迁移及侵袭能力。采用生物信息学方法分析预测miR-515-5p的下游靶基因,双荧光素酶报告基因实验验证组蛋白去乙酰化酶2(histone deacetylase 2,HDAC2)为miR-515-5p的靶基因。应用GEPIA和TCGA数据集分析HDAC2在食管癌组织中的表达及其与患者临床特征的关系。结果：miR-515-5p在食管癌组织及细胞中表达降低（均P<0.01）。过表达miR-515-5p抑制食管癌Eca109细胞...     

Hexokinase 2在卵巢癌中的表达及临床病理意义

目的：探讨卵巢癌中Hexokinase 2（HK-2）表达的临床病理意义。方法：免疫组化检测56例卵巢癌组织及10例癌旁组织中HK-2的表达情况,并对临床病理数据进行分析。MTT法和流式细胞分析分别检测siRNA沉默HK-2蛋白对卵巢癌Skov3细胞增殖及凋亡的影响。Western Blot检测凋亡蛋白Caspase-3的表达。结果：10例癌旁组织中均未见HK-2阳性表达,56卵巢癌中HK-2的阳性表达率为53.6%（30/56）。HK-2高表达与卵巢癌患者肿瘤分期较高（P＝0.018）、肿瘤淋巴结转移密切相关（P＝0.035）,但与患者年龄（P＝0.410）、肿瘤组织学分级（P＝0.108）、肿瘤组织学类型（P＝0.122）、复发（P＝0.160）无显著相关性。siRNA沉默HK-2蛋白抑制卵巢癌Skov3细胞增殖,促进凋亡。Western Blot检测蛋白提示siRNA沉默HK-2蛋白促进了调亡蛋白Caspase-3的表达。结论：卵巢癌中存在HK-2高表达,HK-2在卵巢上皮癌可能发挥了促进肿瘤发生和进展的重要作用,可能是一种新的上皮卵巢癌治疗靶点。     

Epigenetic regulation of RGS2 (Regulator of G-protein signaling 2) in chemoresistant ovarian cancer cells

Regulator of G-protein signaling 2 (RGS2) is a GTPase-activating protein functioning as an inhibitor of G-protein coupled receptors (GPCRs). RGS2 dysregulation was implicated in solid tumour development and RGS2 downregulation has been reported in prostate and ovarian cancer progression. However, the molecular mechanism by which RGS2 expression is suppressed in ovarian cancer remains unknown. The expression and epigenetic regulation of RGS2 in chemosensitive and chemoresistant ovarian cancer cells were determined by qRT-PCR and chromatin immunoprecipitation assays, respectively. In the present study, the molecular mechanisms contributing to the loss of RGS2 expression were determined in ovarian cancer. The data indicated that suppression of RGS2 gene in chemoresistant ovarian cancer cells, in part, due to accumulation of histone deacetylases (HDACs) and DNA methyltransferase I (DNMT1) at the promoter region of RGS2. Inhibition of HDACs or DNMTs significantly increases RGS2 expression. These results suggest that epigenetic changes in histone modifications and DNA methylation may contribute to the loss of RGS2 expression in chemoresistant ovarian cancer cells. The results further suggest that class I HDACs and DNMT1 contribute to the suppression of RGS2 during acquired chemoresistance and support growing evidence that inhibition of HDACs/DNMTs represents novel therapeutic approaches to overcome ovarian cancer chemoresistance.     

Improved survival for BRCA2-associated serous ovarian cancer compared with both BRCA-negative and BRCA1-associated serous ovarian cancer

BACKGROUND:

Multiple observational studies have suggested that breast cancer gene (BRCA)‐associated ovarian cancers have improved survival compared with BRCA‐negative ovarian cancers. However, most of those studies combined BRCA1 and BRCA2 patients or evaluated only BRCA1 patients. The objective of the current study was to examine whether BRCA1‐associated and BRCA2‐associated ovarian cancers were associated with different outcomes.

METHODS:

This was a single‐institution, retrospective analysis of patients who had a new diagnosis of histologically confirmed stage III or IV serous ovarian, fallopian tube, or primary peritoneal cancer between January 1, 1996 and February 1, 2011 and who underwent BRCA mutation testing on 1 of 2 institutional review board‐approved follow‐up studies. Patients who had been tested for BRCA mutations beyond 24 months of diagnosis were excluded from analysis to minimize selection bias from including patients who were referred for genetic testing because of long survival.

RESULTS:

Data from 190 patients (143 BRCA‐negative patients, 30 BRCA1‐positive patients, and 17 BRCA2‐positive patients) were analyzed. During the study period, 73 deaths were observed (60 BRCA‐negative patients, 10 BRCA1‐positive patients, 3 BRCA2‐positive patients). The median follow‐up for the remaining 117 survivors was 2.5 years. At 3 years, 69.4%, 90.7%, and 100% of BRCA‐negative patients, BRCA1‐positive patients, and BRCA2‐positive patients were alive, respectively. On univariate analysis, age, BRCA2 mutations, debulking status, and type of first‐line therapy (intravenous or intraperitoneal) were significant predictors of overall survival. On multivariate analysis, BRCA2 mutations (hazard ratio, 0.20; 95% confidence interval, 0.06‐0.65; P = .007), but not BRCA1 mutations (hazard ratio, 0.70; 95% confidence interval, 0.36‐1.38; P = .31), predicted for improved overall survival compared with BRCA‐negative patients. When carriers of BRCA2 mutations were directly compared with carriers of BRCA1 mutations, BRCA2 mutations appeared to confer improved overall survival (hazard ratio, 0.29; 95% confidence interval, 0.08‐1.05; P = .060), although this finding did not reach significance.

CONCLUSIONS:

The current data suggests that BRCA2 mutations confer an overall survival advantage compared with either being BRCA‐negative or having a BRCA1 mutation in high‐grade serous ovarian cancer. This finding may have important implications for clinical trial design. Cancer 2012. © 2011 American Cancer Society.     

组蛋白去乙酰化酶抑制剂在HR阳性HER-2阴性晚期乳腺癌的研究进展

组蛋白去乙酰化酶（histone deacetylase,HDAC）是可调节表观遗传学改变的组蛋白修饰酶,在一些肿瘤中HDACs被异常激活,与肿瘤进展和耐药密切相关。HDAC抑制剂（HDAC inhibitor,HDACi）通过调节肿瘤细胞的表观遗传属性,靶向性控制肿瘤细胞增殖、调节肿瘤细胞周期及修复DNA损伤。HDACi可抑制多个乳腺癌致癌信号通路,从而有可能逆转激素受体（hormone receptor,HR）阳性HER-2阴性乳腺癌的治疗耐药。本文将对HDACi在HR阳性HER-2阴性晚期乳腺癌治疗方面进行综述,探讨其在乳腺癌治疗领域中的应用前景。     

A comparative analysis of inhibitors of the glycolysis pathway in breast and ovarian cancer cell line models

Many cancer cells rely on aerobic glycolysis for energy production and targeting of this pathway is a potential strategy to inhibit cancer cell growth. In this study, inhibition of five glycolysis pathway molecules (GLUT1, HKII, PFKFB3, PDHK1 and LDH) using 9 inhibitors (Phloretin, Quercetin, STF31, WZB117, 3PO, 3-bromopyruvate, Dichloroacetate, Oxamic acid, NHI-1) was investigated in panels of breast and ovarian cancer cell line models. All compounds tested blocked glycolysis as indicated by increased extracellular glucose and decreased lactate production and also increased apoptosis. Sensitivity to several inhibitors correlated with the proliferation rate of the cell lines. Seven compounds had IC₅₀ values that were associated with each other consistent with a shared mechanism of action. A synergistic interaction was revealed between STF31 and Oxamic acid when combined with the antidiabetic drug metformin. Sensitivity to glycolysis inhibition was also examined under a range of O₂ levels (21% O₂, 7% O₂, 2% O₂ and 0.5% O₂) and greater resistance to the inhibitors was found at low oxygen conditions (7% O₂, 2% O₂ and 0.5% O₂) relative to 21% O₂ conditions. These results indicate growth of breast and ovarian cancer cell lines is dependent on all the targets examined in the glycolytic pathway with increased sensitivity to the inhibitors under normoxic conditions.     

The inhibiting effects of Laggera alata flavone on human ovarian cancer HO-8910 cells proliferation and its mechanism in vitro

The purpose of this study was to investigate the effect of Laggera alata flavonen （LAF） on the inhibit- ing effect of human ovarian cancer HO-8910 cells proliferation and its possible mechanism in vitro. Methods： Human ovarian cancer HO-8910 cells were cultured in vitro. Inhibitory effect of LAF on the viability of HO-8910 cells was evaluated by the MTT assay. Apoptotic effect of different concentrations of LAF on HO-8910 cells was assessed by AO/EB staining and FCM with propidium iodide （PI） staining. Expression of proteins related to apoptosis was analyzed by Western blot. Results： LAF significantly inhibited the viability of HO-8910 cells proliferation in a dose-dependent and time-dependent manner, there were statistical significance compared with NS group （P 〈 0.05）, and the ICso was 4.28 pg/mL for 48 h. The cells treated with LAF showed typical morphological change and apoptotic rate increased by FCM in a dose-dependent, and there was notable dif- ference compared with NS group （P 〈 0.05）. Western blot showed that expression of Fas, caspase-8, tBid and Cyto-c proteins were up-regulated after treatment with LAF for 48 h in a concentration dependent. Conclusion： LAF could inhibit HO-8910 cells proliferation and induce apoptosis, which may be through the pathway of death receptor in vitro.     

H2AX磷酸化抑制肺癌细胞发生上皮-间质转化的作用机制

背景 与目的:上皮-间质转化(epithelial-to-mesenchymal transition,EMT)是肿瘤细胞发生转移的关键生物学过程,阻碍EMT将抑制肿瘤转移,因此阐明EMT的分子机制具有重要意义.抑癌蛋白H2AX调控肿瘤细胞凋亡相关基因表达,进而产生抗肿瘤作用.揭示H2AX与EMT的关系,探讨H2AX调...     

MS-275 synergistically enhances the growth inhibitory effects of RAMBA VN/66-1 in hormone-insensitive PC-3 prostate cancer cells and tumours

Combining drugs, which target different signalling pathways, often decreases adverse side effects while increasing the efficacy of treatment. The objective of our study was to determine if the combination of our novel atypical retinoic acid metabolism-blocking agent (RAMBA) VN/66-1 and a promising histone deacetylase inhibitor N-(2-aminophenyl)4-[N-(pyridine-3-yl-methoxy-carbonyl)aminomethyl]benzamide (MS-275) would show enhanced antineoplastic activity on human PC-3 prostate cancer cells/tumours and also to decipher the molecular mechanisms of action. The combination of VN/66-1+MS-275 was found to be synergistic in inhibiting PC-3 cell growth, caused cell cytostaticity/cytotoxicity and induced marked G2/M phase arrest and apoptosis. In mice with well-established PC-3 tumours, VN/66-1 (5 and 10 mg kg(-1) day(-1)) caused significant suppression of tumour growth compared with mice receiving vehicle alone. Furthermore, treatment with VN/66-1 (10 mg kg(-1) day(-1))+MS-275 (2.5 mg kg(-1) day(-1)) for 18 days resulted in an 85% reduction in final mean tumour volume compared with control and was more effective than either agent alone. Mechanistic studies indicated that treatment of PC-3 cells/tumours with VN/66-1+MS-275 caused DNA damage (upregulation of gammaH2AX), hyperacetylation of histones H3 and H4, upregulation of retinoic acid receptor-beta, p21WAF1/CIP1, E-cadherin, and Bad and downregulation of Bcl-2. These data suggest that the mechanism of action of the combination of agents is DNA damage-induced p21 activation, resulting in inhibition of the Cdc2/cyclin B complex and accumulation of cells in G2/M phase. In addition, the combination caused modulation and induction of apoptosis. These results suggest that VN/66-1 or its combination with MS-275 may be a novel therapy for the treatment of prostate carcinoma.     

The histone deacetylase inhibitor, suberoylanilide hydroxamic acid, overcomes resistance of human breast cancer cells to Apo2L/TRAIL

While the apoptosis-inducing ligand Apo2L/TRAIL is a promising new agent for the treatment of cancer, the sensitivity of cancer cells for induction of apoptosis by Apo2L/TRAIL varies considerably. Identification of agents that can be used in combination with Apo2L/TRAIL to enhance apoptosis in breast cancer cells would increase the potential utility of this agent as a breast cancer therapeutic. Here, we show that the histone deacetylase inhibitor, suberoylanilide hydroxamic acid (SAHA), can sensitize Apo2L/TRAIL-resistant breast cancer cells to Apo2L/TRAIL-induced apoptosis. Importantly, neither Apo2L/TRAIL alone, nor in combination with SAHA, affected the viability of normal human cells in culture. Apo2L/TRAIL-resistant MDA-MB-231 breast cancer cells, generated by long-term culture in the continuous presence of Apo2L/TRAIL, were resensitized to Apo2L/TRAIL-induced apoptosis by SAHA. The sensitization of these cells by SAHA was accompanied by activation of caspase 8, caspase 9 and caspase 3 and was concomitant with Bid and PARP cleavage. The expression of the proapoptotic protein, Bax, increased significantly with SAHA treatment and high levels of Bax were maintained in the combined treatment with Apo2L/TRAIL. Treatment with SAHA increased cell surface expression of DR5 but not DR4. Interestingly, SAHA treatment also resulted in a significant increase in cell surface expression of DcR1. Taken together, our findings indicate that the use of these 2 agents in combination may be effective for the treatment of breast cancer.     

Tribbles 2 mediates cisplatin sensitivity and DNA damage response in epithelial ovarian cancer

Aim was to identify methylated genes with functional involvement in cisplatin‐resistance development of epithelial ovarian cancer (EOC). Genome‐wide analyses of hypermethylated CpG‐islands in resistant cell lines in combination with qRT‐PCR analyses were used to identify epigenetically silenced genes. EOC‐Type‐II tumors were analyzed for gene methylation and expression and TCGA data were interrogated in‐silico. Experiments revealed 37 commonly hypermethylated genes in resistant cells of which Tribbles 2 (TRIB2) showed the most pronounced downregulation on mRNA level and was characterized further. TRIB2 showed a reactivation after 5′‐Aza‐Cytidine treatment in resistant cells but a cisplatin‐dependent, prominent upregulation on mRNA level in sensitive cells, only. Re‐expression in resistant A2780 cells increased the sensitivity to cisplatin and other DNA‐damaging agents, but not taxanes. Contrary, knockdown of TRIB2 increased resistance to cisplatin in sensitive cells. TRIB2 was involved in the induction of a cisplatin‐dependent cell cycle arrest and apoptosis by influencing p21 and survivin expression. An increased Pt‐DNA‐adduct formation in TRIB2 re‐expressing cells did not translate in higher levels of dsDNA damage (yH2AX‐foci). Thus, TRIB2 is potentially involved in the signal transduction from nucleotide excision repair of intrastrand cross links. Importantly, patient stratification of two homogenous cohorts of EOC‐Type‐II patients from Jena (n = 38) and the TCGA (n = 149) by TRIB2 mRNA expression consistently revealed a significantly decreased PFS for patients with low TRIB2 levels (log‐rank p < 0.05). Tumors from resistant patients expressed the lowest levels of TRIB2. Downregulation of TRIB2 contributes to platin‐resistance and TRIB2 expression should be validated as prognostic and predictive marker for EOC.     

Cytotoxic activity of the histone deacetylase inhibitor panobinostat (LBH589) in anaplastic thyroid cancer in vitro and in vivo

Anaplastic thyroid carcinoma (ATC) has a rapidly fatal clinical course, being resistant to multimodal treatments. Microtubules, α/β tubulin heterodimers, are crucial in cell signaling, division and mitosis and are among the most successful targets for anticancer therapy. Panobinostat (LBH589) is a potent deacetylase inhibitor acting both on histones and nonhistonic proteins, including α-tubulin. In vitro LBH589, evaluated in three ATC cell lines (BHT-101, CAL-62 and 8305C), resulted in impairment of cell viability, inhibition of colony formation, cell cycle arrest and apoptosis induction. Mechanistically, we showed that LBH589 not only affected the expression of p21 and cyclin D1, but markedly determined microtubule stabilization as evidenced by tubulin acetylation and increased tubulin polymerization. In a SCID xenograft model implanted with CAL-62 cells, the cytotoxic properties of LBH589 were confirmed. The drug at the dose of 20 mg/kg significantly impaired tumor growth (final tumor volume 2.5-fold smaller than in untreated animals); at this dose, no relevant side effects were observed. In tumors of treated animals, a significant reduction of Ki67, which was negatively correlated with tubulin acetylation, was observed. Moreover, acetyl-tubulin levels negatively correlated with tumor volume at sacrifice, reinforcing the opinion that tubulin acetylation has a role in the inhibition of tumor growth. In conclusion, LBH589, acting on both histones and nonhistonic proteins in anaplastic thyroid cancer, appears to be a promising therapeutic agent for the treatment of this kind of cancer which is known not to respond to conventional therapy.     

Proton pump inhibitors enhance the effects of cytotoxic agents in chemoresistant epithelial ovarian carcinoma

This study was designed to investigate whether proton pump inhibitors (PPI, V-ATPase blocker) could increase the effect of cytotoxic agents in chemoresistant epithelial ovarian cancer (EOC). Expression of V-ATPase protein was evaluated in patients with EOC using immunohistochemistry, and patient survival was compared based on expression of V-ATPase mRNA from a TCGA data set. In vitro, EOC cell lines were treated with chemotherapeutic agents with or without V-ATPase siRNA or PPI (omeprazole) pretreatment. Cell survival and apoptosis was assessed using MTT assay and ELISA, respectively. In vivo experiments were performed to confirm the synergistic effect with omeprazole and paclitaxel on tumor growth in orthotopic and patient-derived xenograft (PDX) mouse models. Expression of V-ATPase protein in ovarian cancer tissues was observed in 44 patients (44/59, 74.6%). Higher expression of V-ATPase mRNA was associated with poorer overall survival in TCGA data. Inhibition of V-ATPase by siRNA or omeprazole significantly increased cytotoxicity or apoptosis to paclitaxel in chemoresistant (HeyA8-MDR, SKOV3-TR) and clear cell carcinoma cells (ES-2, RMG-1), but not in chemosensitive cells (HeyA8, SKOV3ip1). Moreover, the combination of omeprazole and paclitaxel significantly decreased the total tumor weight compared with paclitaxel alone in a chemoresistant EOC animal model and a PDX model of clear cell carcinoma. However, this finding was not observed in chemosensitive EOC animal models. These results show that omeprazole pretreatment can increase the effect of chemotherapeutic agents in chemoresistant EOC and clear cell carcinoma via reduction of the acidic tumor microenvironment.