Deciphering resistancemechanisms and novel strategies to overcome drug resistance in ovarian cancer:a comprehensive review

Ovarian cancer is among the most lethal gynecological cancers,primarily due to the lack of specific symptoms leading to an advanced-stage diagnosis and resistance to chemotherapy.Drug resistance(DR)poses the most significant challenge in treating patients with existing drugs.The Food and Drug Administration(FDA)has recently approved three new therapeutic drugs,including two poly(ADP-ribose)polymerase(PARP)inhibitors(olaparib and niraparib)and one vascular endothelial growth factor(VEGF)inhibitor(bevacizumab)for maintenance therapy.However,resistance to these new drugs has emerged.Therefore,understanding the mechanisms of DR and exploring new approaches to overcome them is crucial for effective management.In this review,we summarize the major molecular mechanisms of DR and discuss novel strategies to combat DR.

Difference in Expression of Bcl-2 and Bcl-xl Genes in Cisplatin-sensitive and Cisplatin-resistant Human in Ovarian Cancer Cell Lines

To investigate the expression of Bcl-2 and Bcl-xl gene in sensitive (A2780) and drug-resistance (AD6) human ovarian cancer cell lines and explore the molecular mechanism of multidrug resistance, A2780 and AD6 were detected by using DNA gel electrophoresis, flow cytometry and RT-PCR. Our results showed that (1)'DNA ladder ' was observed in A2780 and AD6 after cisplatin treatment; (2) after 3.0, 6.0, 9.9 μg/ml of cisplatin treatment, a significant difference was noted in the rate of apoptosis between in A2780 and AD6 (P<0.05); (3) Bcl-2 and Bcl-xl genes were overexpressed in AD6. After cisplatin treatment, the expression of Bcl-2 and Bcl-xl genes was down-regulated in A2780 and AD6. It is concluded that cisplatin could induce the apoptosis of ovarian cancer cells, and the over-expression of Bcl-2 and Bcl-xl genes may contribute to apoptotic inhibition and the development of multidrug-resistance of human ovarian cancer.

Genetic features of platinum-resistant ovarian cancer patients

The authors try to decide a problem of ovarian cancer resistance to platinum drugs by the way of correlation finding between platinum-resistance of tumor and presence of gene mutations in the patient.It was shown a variety of options for BRCA gene mutations in patients with ovarian cancer:BRCA 1(185delAG)-64.2%,BRCA 1(5382 insC)-55.7%,and BRCA 2(6174delT)-53.8%.Authors discovered a significant positive correlation between carriage of mutations in the BRCA genes 1/2 and the sensitivity of malignant ovarian tumors to chemotherapy with platinum.Mutations in these genes occurred significantly more often in patients with platinum-sensitive ovarian cancer.

A Pilot Study of Gemcitabine and Epirubicin Combination Chemotherapy as a Salvage Regimen for Recurrent Platinum Resistant and/or Refractory Epithelial Ovarian Cancer

BACKGROUND AND OBJECTIVES: The objective of this study was to assess the antitumor activity and toxicity profile of gemcitabine combined with epirubicin in patients with recurrent platinum refractory ovarian epithelial cancer. PATIENTS AND METHODS: Patients with recurrent platinum refractory ovarian cancer and with adequate hematologic, renal and hepatic function and an Eastern Cooperative Oncology Group (ECOG) performance status of 0 - 2 were enrolled. The regimen was Gemcitabine 1000 mg/m2 (day 1, 8) and Epirubicin 60 mg/m2 (day 1), the cycle was repeated at interval of 21 days. RESULTS: Twenty eight patients were recruited and received 156 cycles of gemcitabine-epirubicin combination chemotherapy (median 6 cycles). Overall response rate was 42.9% (95% CI equal 24.5 to 62.7) and tumor control rate was 75% (95% CI equal 55.1 to 89.3). No complete responses were observed. Median progression-free and median overall survival times were 7 and 15 months, respectively. The most common grade 3/4 hematological toxicities were neutropenia (57.1%), anemia (10.7%), and thrombocytopenia (7.1%), while the most common grade 3/4 non-hematological toxicities were mucositis (14.3%) and vomiting (3.6%). No treatment related deaths were observed. CONCLUSION: Gemcitabine combined with epirubicin regimen appeared to offer an acceptable clinical profile in patients with recurrent platinum-refractory epithelial ovarian cancer.

Comparative analysis of ATP-based tumor chemosensitivity assay-directed chemotherapy versus physician-decided chemotherapy in platinum-resistant recurrent ovarian cancer

Objective The aim of the study was to evaluate the role of ATP-based tumor chemosensitivity assay(ATP-TCA) in patients with platinum-resistant recurrent ovarian cancer(PRROC).Methods A total of 43 patients with PRROC who underwent chemotherapy based on the results of ATPTCA in the Cancer Hospital,Chinese Academy of Medical Sciences were included in the present study.As controls,we selected another 43 patients with PRROC who were treated at the physician's discretion within the same time period and had the same clinical characteristics as the patients in the ATP-TCA group.Logrank test and Cox proportional hazards model were adopted for analysis.Results A total of 86 patients were retrospectively analyzed in the present study.Patients were routinely monitored to evaluate the rate of progression-free survival(PFS).The median follow-up time was 13 months.The PFS for the ATP-TCA and control groups was 5 and 3 months,respectively(P = 0.027).Multivariate analysis showed that the type of treatment was an independent prognostic factor for PFS(P = 0.040;HR:0.623;95% CI:0.313–0.973).Subgroup analysis showed that among patients with a treatmentfree interval(TFI) of ≥ 3 months(n = 50),those in the ATP-TCA group had longer PFS than those in the control group(7 vs 4 months,P = 0.010).Meanwhile,the median PFS of patients who underwent ≤ 2 prior chemotherapy regimens(PCR,n = 52) in the ATP-TCA and control groups was 6 months and 4 months,respectively(P = 0.025).Conclusion ATP-TCA-directed chemotherapy might improve the PFS in PRROC.In particular,the survival benefit from ATP-TCA is higher in patients with a TFI of ≥ 3 months or treated with ≤ 2 PCR.

Expression of cyclooxygenase-2 mRNA in drug-sensitive cell and drug-resistant strains of ovarian cancer cell lines

Objective： To investigate the expression of cyclooxygenase-2 （COX-2） mRNA in drug-sensitive cell and drugresistant clones of ovarian cancer cell lines. Methods： RT-PCR and immunocytochemistry were used to investigate the expression of cyclooxygenase-2 in 3 clones drug-sensitive and 5 clones drug-resistant ovarian cancer cell. Results： Strong COX-2 mRNA expressions were detected in 3 clones of drug-sensitive cell and weak expressions were detected in 5 clones of drug-resistant cell. The protein expression of COX-2 in drug-sensitive cell was strongly positive reaction in immunocytochemistry stain and there was a weak positive reaction in 5 clones of drug-resistant cell. Conclusion： The expression of COX-2 mRNA in drug-sensitive cell strains is much higher than that in drugresistant strains of ovarian cancer cell lines, providing a basis of the chemoprevention for ovarian cancer.

Apoptosis Rate and Objective Diagnosis of Drug Resistance of Ovarian Cancer Cell Lines

Objective： To investigate whether the change of drug resistance degree could be evaluated by apoptotic rate in ovarian cancer cell lines. Methods： Human epithelia ovarian cancer cell line A2780 and its platinum （DDP） resistance cell line AD4 were used. They were divided into 4 groups respectively （A2780-DDP group, A2780-DDP＋VRM group, AD4-DDP group and AD4-DDP＋VRM group）. 3-（4, 5- dimethylthiazol-2-yl）-2, 5-diphenyl-2H-tetrazolium bromide （MTT） was used to measure the multiple of drug resistance. The expression of drug-resistance genes （mdrl, TopoⅡα and GSTπ） was detected by using reverse transcription polymerase chain reaction （RT-PCR）. Semi-quantity assay was proceed by rate the of multidrug resistance genes to G3 PDH gene. Apoptosis was measured by DNA gel electrophoresis and flow cytometry respectively. The advantages and disadvantage of evaluating drug-resistance with these three methods were analyzed. Results： The 50% inhibition concentration （IC50） of A2780 and AD4 was 19.2 μg/mL and 66 μg/mL respectively, and the resistance fold of the AD4 was 3.4. Some drug-resistance genes could be detected by RT-PCR in A2780 and AD4 cell lines. The expression of mdrl was only （0.09±0.03）×10^-2 ： 1 and （0.10±0.02） × 10^-2：1 respectively （rate to G3 PDH gene） with the difference being not significant between them. The expression of TopoⅡα in the A2780 cells was （2.60±0.12）×10^-2：1 and （0.11±0.03）× 10^-2：1 in the AD4 cells respectively with the difference between them being significant. On the contrary, the expression of GSTπ in A2780 cells was lower than in AD4 cells, and the ratio was （0.11±0.03）×10^-2：1 and （3.13±0.14）×10^-2：1 respectively with tile difference being significant between them. There was no significant difference among the genes expression after the drugs were given for 6 h, 12 h and 24 h. couldn＇t reflect the change of drug-resistance timely. DNA gel electrophoresis used to detect apoptosis was only a qualitative analysis. Different drug resistance degrees may be detected by flow cytometry as early as few hours after drugs were given, which realized the earlier and quantities detection of drug resistance. Conclusion： Detection of apoptosis with flow cytometry may not be affected by the variety of drug-resistance genes, suggested this was a general, quantitative and objective method to reflect drug resistance.

miR-125b Confers Resistance of Ovarian Cancer Cells to Cisplatin by Targeting Pro-apoptotic Bcl-2 Antagonist Killer 1

Chemotherapy is the preferred therapeutic approach for advanced ovarian cancer,but a successful long-term treatment is prevented by the development of drug resistance.Recent works have underlined the involvement of non-coding RNAs,microRNAs（miRNAs） in cancer development,with several conjectures regarding their possible involvement in the evolution of drug resistance.This study is to investigate the promoting effects and mechanism of miR-125b involved in the development of chemoresistance in ovarian cancer.The different expression of miR-125b in cisplatin-sensitive ovarian cancer cell line（OV2008） and its resistant variant（C13＊） was identified by real-time PCR.An in vitro cytotoxicity assay and apoptosis assay using CCK-8 assay and flow cytometry,were carried out to detect the effect of miR-125b and Bak1 on cisplatin resistance of cells.Real-time PCR,Western blotting and luciferase reporter assay were used to detect whether Bak1 is a target of miR-125b.As compared with OV2008 cells,the expression levels of miR-125b in C13＊ cells were increased.It was found that the up-regulation of microRNA-125b caused a marked inhibition of cisplatin-induced cytotoxicity and apoptosis and a subsequent increase in the resistance to cisplatin in OV2008 and C13＊ cells.Moreover,Bak1 was a direct target of miR-125b,and down-regulation of Bak1 suppressed cisplatin-induced apoptosis and led to an increased resistance to cisplatin.Our study indicates that miR-125b has a significantly promoting effect on chemoresistance of C13＊ cells and up-regulation of miR-125b expression contributes to cisplatin resistance through suppression of Bak1 expression.This finding has important implications in the development of targeted therapeutics for overcoming cisplatin resistance in ovarian cancer.

Reversal of Multidrug Resistance and Inhibition of Phosphorylation of AKT in Human Ovarian Cancer Cell Line by Wild-type PTEN Gene

The reversing effect of wild-type PTEN gene on resistance of C 13K cells to cisplatin and its inhibitory effect on the phosphorylation of protein kinase B （AKT） were studied. The expression of PTEN mRNA and protein in OV2008 cells and C13K cells were semi-quantitatively detected by using RT-PCR and Western blotting. Recombinant eukaryotic expression plasmid containing human wild-type PTEN gene was transfected into C13K cells by lipofectamine2000. The expression of PTEN mRNA was monitored by RT-PCR and the expression of PTEN, Akt, p-Akt protein were ana- lyzed by Western blotting in PTEN-transfected and non-transfected C13K cells. Proliferation and chemosensitivity of cells to DDP were measured by MTT, and cell apoptosis was detected by flow cytometry after treatment with cisplatin. The expression of PTEN mRNA and protein in OV2008 cells were significantly higher than those in C13K cells. After transfection with PTEN gene for 48 h, the expression of PTEN mRNA and protein in C 13K cells were 2.04 ± 0.10, 0.94± 0.04 respectively and the expression of p-Akt protein （ 0.94± 0.07） was lower than those in control groups （1.68 ±0.14, 1.66± 0.10） （P〈 0.05）. The IC50 of DDP to C 13 K cells transfected with PTEN （7.2± 0.3 la mol/L） was obviously lower than those of empty-vector transfected cells and non-transfected cells （12.7±0.4 lamol/1, 13.0±0.3 lamol/L） （P〈0.05）. The apopototis ratio of wild-type PTEN-transfected, empty vector transfected and non-transfected C13K cells were （41.65___0.87）%, （18.61 ±0.70）% and （15.28±0.80）% respectively, and the difference was statistically significant （P〈0.05）. PTEN gene plays an important role in ovarian cancer multidrug resistance. Transfection of PTEN could increase the expression of PTEN and restore drug sensitivity to cisplatin in human ovarian cancer cell line C 13K with multidrug-resistance by decreasing the expression of p-Akt.

Role of CD24 in Anoikis Resistance of Ovarian Cancer Cells

This study examined the effect of CD24 on anoikis of ovarian cancer cells. The expres- sion of CD24 was detected by RT-PCR and Western blotting in ovarian cancer cells with high metas- tatic potential （HO-8910PM cells） and low metastatic potential （A2780 cells）. Cell viability and cell proliferation were detected by MTT assay in suspension culture and adhesion culture. Soft agar cul- ture was used to observe the colony formation. Anoikis was flow cytometrically detected. The results showed that the expression levels of CD24 mRNA and protein were significantly higher in HO-8910PM cells than in A2780 cells （P〈0.01）. In the suspension culture and soft agar culture, the HO-8910PM cells formed larger and more colonies （35.334-5.51 vs. 16.674-4.04; P〈0.01）, and showed a stronger resistance to anoikis than A2780 cells did （cell apoptosis rate： 5.93%4-2.38% vs. 16.32%-4-2.00%; P〈0.01）. After treated with CD24 monoclonal antibodies, the number of colony formed in HO-8910PM and A2780 cells was significantly decreased （9.334-2.52 and 8.004-2.00, re- spectively）, and the anoikis rate of the two cell lines was also markedly increased （23.11%4-2.87% and 28.36%~2.29%, respectively）. Our study suggested that CD24 may play an important role in the development of anoikis resistance and CD24 can be used as a new therapeutic target to induce anoikis and inhibit metastasis in ovarian cancer.

MiR-106a Targets Mcl-1 to Suppress Cisplatin Resistance of Ovarian Cancer A2780 Cells

Summary： Resistance to chemotherapy is a major obstacle for the effective treatment of advanced ovarian cancer. The mechanism of chemoresistance is still poorly understood. Recently, more and more evidence showed microRNAs （miRNAs） modulated many key molecules and pathways involved in chemotherapy, microRNA-106a （miR-106a） has been implicated in many cancers, but its role in ovarian cancer and drug resistance still remains unexplored. This study was to investigate whether miR-106a mediated resistance of the ovarian cancer cell line A2780 to the chemotherapeutic agent cisplatin （DDP）. The different levels of miR-106a in A2780 cells and their resistant variant A2780/DDP cells were identified by using real-time PCR. MTT assay and flow cytometry were used to analyze the effect of miR-106a on cisplatin resistance of these paired cells. Real-time PCR, Western blotting and luciferase reporter assay were applied to explore whether Mcl-1 was a target of miR-106a. As compared to A2780 cells, the expression of miR-106a was down-regulated in the cisplatin resistant cell line A2780/DDP. Moreover, knockdown of miR-106a dramatically decreased antiproliferative effects and apoptosis induced by cisplatin in A2780 cells, while overexpression of miR-106a significantly increased antiproliferative effects and apoptosis induced by cisplatin in A2780/DDP cells. Furthermore, miR-106a inhibited cell survival and cisplatin resistance through downregulating the expression of Mcl-1. Mcl-1 was a di- rect target of miR-106a. These results suggest that miR-106a may provide a novel mechanism for un- derstanding cisplatin resistance in ovarian cancer by modulating Mcl-1.

MicroRNA-mRNA functional pairs for cisplatin resistance in ovarian cancer cells

Ovarian cancer is the leading cause of death in women worldwide. Cisplatin is the core of first-line chemotherapy for patients with advanced ovarian cancer. Many patients eventually become resistant to cisplatin, diminishing its therapeutic effect. MicroRNAs(miRNAs) have critical functions in diverse biological processes. Using miRNA profiling and polymerase chain reaction validation, we identified a panel of differentially expressed miRNAs and their potential targets in cisplatin-resistant SKOV3/DDP ovarian cancer cells relative to cisplatin-sensitive SKOV3 parental cells. More specifically, our results revealed significant changes in the expression of 13 of 663 miRNAs analyzed, including 11 that were up-regulated and 2 that were down-regulated in SKOV3/DDP cells with or without cisplatin treatment compared with SKOV3 cells with or without cisplatin treatment. miRNA array and mRNA array data were further analyzed using Ingenuity Pathway Analysis software. Bioinformatics analysis suggests that the genes ANKRD17, SMC1A, SUMO1, GTF2H1, and TP73, which are involved in DNA damage signaling pathways, are potential targets of miRNAs in promoting cisplatin resistance. This study highlights candidate miRNAmRNA interactions that may contribute to cisplatin resistance in ovarian cancer.

Chitosan/pshRNA Plasmid Nanoparticles Targeting MDR1 Gene Reverse Paclitaxel Resistance in Ovarian Cancer Cells

In order to investigate the effect of chitosan/pshRNA plasmid nanoparticles targeting MDR1 genes on the resistance of A2780/TS cells to paclitaxel, chitosan/pshRNA plasmid nanoparti- cles were synthesized by means of a complex coacervation technique and transfected into A2780/TS cells. The cells transfected with MDRl-targeted chitosan/pshRNA plasmid nanoparticles were experimental cells and the cells transfected with chitosan/pGPU6/GFP/Neo no-load plasmid nanoparticles served as negative control cells. Morphological features of the nanoparticles were observed under transmission electron microscope （TEM）. MDR1 mRNA expression was assessed by RT-PCR. Half-inhibitory concentration （IC50） ofpaclitaxel for A2780/TS cells was determined by MTT method. TEM showed that the nanoparticles were round-shaped, smooth in surface and the diameters varied from 80 to 120 nm. The MDR1 mRNA in the transfected cells was significantly decreased by 17.6%, 27.8% and 52.6% on the post-transfection day 2, 4 and 7 when compared with that in A2780/TS cells control （P〈0.05）. MTT assay revealed that the relative reversal efficiency was increased over time and was 29.6%, 51.2% and 61.3% respectively in the transfected cells 2, 4, 7 days after transfection and IC_50 （0.197±0.003, 0.144±0.001, 0.120±0.004） were decreased with difference being significant when compared with that in A2780/TS （0.269±0.003） cells control （P〈0.05）. It was concluded that chitosan/pshRNA plasmid nanoparticles targeting MDR1 can effectively reverse the paclitaxel resistance in A2780/TS cells in a time-dependent manner.

Effect of Spindle Checkpoint on Akt2-mediated Paclitaxel-resistance in A2780 Ovarian Cancer Cells

Recent evidence has suggested that Akt2 plays an important role in the protection of cells from paclitaxel （PTX）-induced apoptosis and control of the cell cycle. In addition, some scholars suggested that the PTX sensitivity depends on a functional spindle assembly checkpoint. In the present study, we investigated the role of the Akt2/Bubl cross-talking in apoptosis and cell cycle after exposure of the A2780 ovarian cancer cells to paclitaxel （PTX）. Recombinant expression plasmid WT-Akt2 was transfected into A2780 cells by lipofectamine2000, and then the expression level of Akt2 gene was detected by using RT-PCR and Western blotting. Cell apoptosis and cell cycle were detected by flow cytometry and Hoechst 33342 staining after treatment with PTX. Moreover, we compared the expression level of Bubl in different groups by Western blotting. Our study showed that up-regulation of Akt2 contributed to A2780 ovarian cancer cells overriding PTX-induced G2/M arrest, and inhibited Bubl expression. Our findings might shed light on the molecular mechanism of PTX-induced resistance in ovarian cancer and help develop novel anti-neoplastic strategies.

PRPF6 promotes metastasis and paclitaxel resistance of ovarian cancer via SNHG16/CEBPB/GATA3 axis

Metastasis and paclitaxel(PTX)resistance are the main reason for the poor prognosis of ovarian cancer(OC).Evidence showed that RNA-binding proteins(RBPs)and long noncoding RNAs(lncRNAs)can modulate post-transcriptional regulation.The aim of this study was to determine the relationship among RBP,lncRNA and OC and to further guide clinical therapy.Immunohistochemistry revealed that pre-mRNA processing factor 6(PRPF6)was upregulated in OC chemoresistant tissues and was closely related to advanced(Federation of International of Gynecologists and Obstetricians)FIGO stages and chemo-resistance.PRPF6 promoted progression,and PTX resistance in vitro and in vivo.And the transcripts of small nucleolar RNA host gene SNHG16-L/S were differentially expressed in OC cells and tissues as detected through real-time PCR(RT-PCR).SNHG16-L/S had opposite effects on progression and PTX resistance in OC.Mechanistically,SNHG16-L inhibited GATA-binding protein 3(GATA3)transcription by binding to CCAAT/enhancer-binding protein B(CEBPB).Moreover,PRPF6 induced the alternative splicing of SNHG16,causing downregulation of SNHG16-L and,leading to the upregulation of GATA3 expression to further promote metastasis and PTX-resistance in OC.Totally,these data unveiled that PRPF6 promotes metastasis and PTX resistance of OC through SNHG16-L/CEBPB/GATA3 axis,which provides a new direction for OC treatment.

DNA-repair ERCC1 Gene Polymorphisms in Epithelial Ovarian Cancer and Relation to Platinum Resistance and Survival

Objectives: Excision repair cross-complementation group 1 (ERCC1) is a key DNA repair gene in the nucleotide excision repair pathway which is activated in the repair of intra- and interstrand DNA crosslink caused by platinum-based treatment. Two single nucleotide polymorphisms (SNPs) of the ERCC1 gene, codon 118 C/T and C8092A, have been reported to be functional, but the influence on platinum resistance and survival is not yet clear. The primary aim of the present study was to investigate whether the two SNPs were associated with resistance to standard combination carboplatin and paclitaxel chemotherapy and the potential prognostic impact in newly diagnosed ovarian cancer patients. Methods: Serum samples from 202 patients with newly diagnosed ovarian cancer were assessed for ERCC1 SNP genotyping using real time PCR. All patients were treated with first line carboplatin/paclitaxel chemotherapy. Results: There were no correlation between the ERCC1 118 C/T and C8092A genotypes and platinum resistance (P = 0.79 and P = 0.36, respectively). Furthermore, the results showed no association to progression free survival (P = 0.18 and P = 0.16, respectively) or overall survival (P = 0.89 and P = 0.78, respectively) for the two SNPs. Conclusions: The ERCC1 118 C/T and C8092A polymorphisms did not have significant influence on clinical outcome defined as platinum resistance, PFS and OS.

Cytoplasmic translocation of Cx32 mediates cisplatin resistance in ovarian cancer cells

OBJECTIVE To investigate the underlying mechanism of drug resistance to cisplatin and increasing the sensitivity to therapeutic drugs are key steps towards the improved treatment of patients with ovarian cancer.Gap junction(GJ)and connexin(Cx)are closely related to tumor formation,but the relationship between cisplatin resistance and GJ or Cx are undetermined.METHODS We established the cisplatin-resistant human ovarian cancer cell line A2780-CDDP over an 11-month period,with the concentration of cisplatin gradually increasing from 0.5 g·L^(-1) to 16 g·L^(-1).To explore the effect of GJ in the process of cisplatin resistance,we investigated GJ using a parachute dyecoupling assay in A2780-RI(1.2),A2780-RI(1.7),A2780-RI(2.9),A2780-RI(4.3)and A2780-CDDP cells.We further explored whether the Cxs responsible for GJ were related to cisplatin resistance.In A2780-RI(1.2),A2780-RI(1.7),A2780-RI(2.9),A2780-RI(4.3)and A2780-CDDP,we used q-PCR to analyze the levels of Cx43,Cx40,Cx37,and Cx32.To confirm the effect of Cx32 on cisplatin resistance,we knocked down Cx32 in A2780-CDDP cells with si RNA-Cx32.As GJ was decreased whereas Cx32 expression was elevated during the cisplatin resistance process,it drove us to explore the underlying mechanism.To resolve this issue,we extracted membrane-bound and cytoplasmic proteins from A2780 and A2780-CDDP cells.RESULTS Here we showed that cisplatin resistance was correlated to the loss of GJ and the upregulation of Cx32 expression.Enhancing GJ in A2780-CDDP cells could increase the apoptotic response to cisplatin treatment.Furthermore,although Cx32 expression was increased in A2780-CDDP cells,it was more localized to the cytoplasm rather than in the membrane,and knockdown of Cx32 in A2780-CDDP cells sensitized them to cisplatin treatment.CONCLUSION In summary,Cx32 is involved in cisplatin resistance,and cytoplasmic Cx32 plays an important role in chemoresistance.

Low-dose fractionated radiation reverses cisplatin resistance in ovarian cancer cells via PI3K/AKT/GSK-3β signaling

Objective To investigate whether low-dose fractionated radiation(LDFRT) could enhance cisplatin sensitivity in drug-resistant human ovarian cancer cells SKOV3/DDP, and to further explore the underlying mechanism.Methods SKOV3/DDP ovarian cancer cells were divided into three groups as follows: control, LDFRT, and conventional-dose radiation groups. Cells from all three groups were treated with different concentrations of cisplatin(0, 1.25, 2.5, 5, 10, and 20 μg/m L) for 48 h. The proliferation inhibition rate was investigated using the cell counting kit 8(CCK8). The rate of apoptosis was determined by flow cytometry(FCM). Protein levels of AKT, P-AKT, GSK-3β, P-GSK-3β, P21, cyclin D1, and P27 were examined by Western blotting. Results As expected, LDFRT significantly reduced the half-maximal inhibitory concentration(IC50) of cisplatin and promoted apoptosis in SKOV3/DDP cells. Moreover, in the LDFRT group, protein levels of P-AKT, P-GSK-3β, and cyclin D1 were markedly decreased, those of P21 and P27 were greatly increased, and total AKT and GSK-3β levels showed no significant difference compared to those in both the control and conventional-dose radiation groups.Conclusion LDFRT sensitizes resistant SKOV3/DDP ovarian cancer cells to cisplatin through inactivation of PI3 K/AKT/GSK-3β signaling.

A nanocomposite competent to overcome cascade drug resistance in ovarian cancer via mitochondria dysfunction and NO gas synergistic therapy

Ovarian cancer(OC)is one of the most common and recurring malignancies in gynecology.Patients with relapsed OC always develop"cascade drug resistance"(CDR)under repeated chemotherapy,leading to subsequent failure of chemotherapy.To overcome this challenge,amphiphiles(P1)carrying a nitric oxide(NO)donor(Isosorbide 5-mononitrate,ISMN)and high-density disulfide are synthesized for encapsulatingmitochondria-targeted tetravalent platinum prodrug(TPt)to construct a nanocomposite(INP@TPt).Mechanism studies indicated that INP@TPt significantly inhibited drug-resistant cells by increasing cellular uptake and mitochondrial accumulation of platinum,depleting glutathione,and preventing apoptosis escape through generating highly toxic peroxynitrite anion(ONOO−).To better replicate the microenvironmental and histological characteristics of the drug resistant primary tumor,an OC patient-derived tumor xenograft(PDXOC)model in BALB/c nude mice was established.INP@TPt showed the best therapeutic effects in the PDXOC model.The corresponding tumor tissues contained high ONOO−levels,which were attributed to the simultaneous release of O_(2)^(·−)and NO in tumor tissues.Taken together,INP@TPtbased systematic strategy showed considerable potential and satisfactory biocompatibility in overcoming platinum CDR,providing practical applications for ovarian therapy.

hGBP-1 Expression Predicts Shorter Progression-Free Survival in Ovarian Cancers, While Contributing to Paclitaxel Resistance

Ovarian cancer is the gynecological cancer with the poorest prognosis. One significant reason is the development of resistance to the chemotherapeutic drugs used in its treatment. The large GTPase, hGBP-1, has been implicated in paclitaxel resistance in ovarian cell lines. Forced expression of hGBP-1 in SKOV3 ovarian cancer cells protects them from paclitaxel-induced cell death. However, prior to this study, nothing was known about whether hGBP-1 was expressed in ovarian tumors and whether its expression correlated with paclitaxel resistance. hGBP-1 is expressed in 17% of ovarian tumors from patients that have not yet received treatment. However, at least 80% of the ovarian tumors that recurred after therapies that included a taxane, either paclitaxel or docetaxel, were positive for hGBP-1. In addition, hGBP-1 expression predicts a significantly shorter progression-free survival in ovarian cancers. Based on these studies, hGBP-1 could prove to be a potential biomarker for paclitaxel resistance in ovarian cancer.