Recovery of miR-139-5p in Ovarian Cancer Reverses Cisplatin Resistance by Targeting C-Jun.

In platinum-based chemotherapy for ovarian cancer, acquired drug resistance is a frequent occurrence. Because recent studies have demonstrated that dysregulation of microRNAs (miRNAs) is partly responsible for the induction of acquired drug resistance in cancers, we hypothesized that correcting the dysregulation of key miRNAs would reverse the acquired resistance to platinum-based drugs in ovarian cancer. Cisplatin-resistant SKOV3 and A2780 ovarian cancer cell lines (SKOV3-R and A2780-R, respectively) were established by long-term exposure to cisplatin. MTT assays were performed to evaluate the viability of SKOV3, SKOV3-R, A2780, and A2780-R cells. Quantitative PCR was used to examine the expression of miR-139-5p in these cell lines. The regulatory mechanism was confirmed by western blot analysis and luciferase reporter assays. After treatment with miR-139-5p and cisplatin, mitochondrial membrane potential and apoptosis were measured by using flow cytometry. Interaction with c-Jun and activating transcription factor 2 (ATF2) was evaluated by co-immunoprecipitation. Expression of B-cell lymphoma-extra large (Bcl-xl) and activation of caspase-9 and caspase-3 were detected by western blotting. Expression of miR-139-5p was decreased in SKOV3-R and A2780-R cells. Recovery of miR-139-5p increased the sensitivity of SKOV3-R and A2780-R cells to cisplatin treatment, inhibited the interaction of c-Jun and ATF2, and decreased Bcl-xl expression in SKOV3-R and A2780-R cells. Expression of miR-139-5p promoted cisplatin-induced mitochondrial apoptosis through binding the 3' untranslated region of c-Jun mRNA. Recovery of miR-139-5p suppressed the expression of c-Jun and thus reversed cisplatin-resistance in ovarian cancer.

Jiang Y ，Jiang J ，Jia H ，Qiao Z ，Zhang J ... -  《-》

HDAC1 Silencing in Ovarian Cancer Enhances the Chemotherapy Response.

Cisplatin-based treatment is first-line chemotherapy for several cancers including ovarian cancer. The development of cisplatin resistance results in treatment failure, but the underlying mechanisms are not fully understood. Histone deacetylases (HDACs) are a large family of enzymes that deacetylate lysine residues on histones and non-histone proteins. High expression of HDAC1 is associated with poor outcomes in ovarian cancer. Furthermore, resistance to chemotherapeutic agents is associated with HDAC1 overexpression in ovarian cancer cells. The goals of this study were to determine whether targeting HDAC1 can sensitize ovarian cancer cells to cisplatin and to explore the underlying mechanisms. Small interfering RNA (siRNA)-targeting HDAC1 was designed to silence HDAC1 in the cisplatin-resistant ovarian cancer cell line A2780CDDP and its cisplatin-sensitive cell line A2780. The effects of targeting HDAC1 on cell viability assay, colony formation, and apoptosis were detected. c-Myc re-expression or miR-34a inhibitors were used to examine the relationship among HDAC1, c-Myc, and miR-34a expression, which was assessed by western blot analysis and quantitative reverse transcription PCR. We established stable transfectants of A2780CDDP/HDAC1 short hairpin RNA (shRNA) and A2780/HDAC1 shRNA. The therapeutic effectiveness of cisplatin in murine xenograft models was assessed following shRNA-mediated HDAC1 silencing in A2780CDDP and A2780 cells. The mechanism of cell death was studied in tumor sections obtained from different mouse tumors. In cisplatin-resistant A2780CDDP cells, HDAC1 knockdown by siRNA suppressed cell proliferation, and increased apoptosis and chemosensitivity by downregulating c-Myc and upregulating miR-34a. In cisplatin-sensitive A2780 cells, HDAC1 knockdown did not affect cell proliferation and apoptosis. Cisplatin treatment activated HDAC1 and c-Myc and inactivated miR-34a. Inhibition of HDAC1 with siRNA reduced c-Myc expression, increased miR-34a expression, and sensitized A2780 cells to cisplatin-induced apoptosis. c-Myc re-expression or miR-34a targeting by miR-34a inhibitors protected cells from apoptosis or reversed cisplatin resistance following HDAC1 knockdown or/and cisplatin exposure. Finally, in vivo studies showed that targeting HDAC1 inhibited A2780CDDP-induced xenograft tumor growth but not A2780-induced xenograft tumor growth. Targeting HDAC1 sensitized both A2780- and A2780CDDP-induced xenograft tumors to cisplatin treatment. Upregulation of HDAC1 is a crucial event in the development of drug resistance to current treatments in ovarian cancer. Thus, targeting HDAC1 by enhancing c-Myc-dependent miR-34a expression might be an effective strategy for increasing the efficacy of cisplatin treatment.

Liu X ，Yu Y ，Zhang J ，Lu C ，Wang L ，Liu P ，Song H ... -  《-》

miR-142-5p enhances cisplatin-induced apoptosis in ovarian cancer cells by targeting multiple anti-apoptotic genes.

Chemotherapy is the preferred treatment for advanced ovarian cancer, but the 5-year survival rate remains low partly because of the development of drug resistance. Although it has been reported that X-linked inhibitor of apoptosis (XIAP) causes more severe chemoresistance in ovarian cancer cells and is highly expressed in chemoresistant ovarian cancer, the molecular mechanism underlying this dysregulation is unknown. The purpose of this study was to identify microRNAs (miRNAs) that bind to the 3' untranslated region (3'UTR) of XIAP and have a role in chemoresistance in ovarian cancer. Using in silico analysis and literature review, a panel of miRNAs dysregulated in chemoresistant ovarian cancer was generated from hundreds of miRNAs that were predicted to target the XIAP 3'UTR. Using a dual luciferase reporter assay and cellular co-transfection of a miRNA expression vector and a luciferase reporter fused to the XIAP 3'UTR cognate miRNA binding site, we identified three miRNAs of which miR-142-5p had the greatest inhibitory effect. We found that overexpression of miR-142-5p suppressed XIAP expression by binding to its 3'UTR in OVCAR3 and SKOV3 cells. Using a chemosensitivity assay, we found that in OVCAR3, SKOV3, and primary epithelial ovarian cancer (EOC) cells, overexpression or inhibition of miR-142-5p increased or suppressed their sensitivities to cisplatin respectively. In contrast, introducing XIAP without a 3'UTR counteracted the effect of overexpressed miR-142-5p on cisplatin-induced apoptosis in OVCAR3 ovarian cancer cells. Furthermore, we found a negative correlation between miR-142-5p expression and XIAP protein levels in clinical samples from patients with EOC. Using clinical and miRNA expression data of more than 200 ovarian cancer patients treated with platinum-based chemotherapy from The Cancer Genome Atlas (TCGA) database, we found ovarian cancer patients with higher expression levels of miR-142-5p had longer median progression-free survival as compared to patients with lower miR-142-5p levels. We demonstrated that miR-142-5p also targeted four other anti-apoptotic genes, baculoviral IAP repeat-containing 3 (BIRC3), B-cell lymphoma-2 (BCL2), BCL2 like 2 (BCL2L2), and myeloid cell leukemia sequence 1 (MCL1) specifically. Transcriptome sequencing shed light on the essential apoptosis-related pathway in which miR-142-5p may be involved. To conclude, our findings illustrate that miR-142-5p sensitizes ovarian cancer cells to cisplatin-induced apoptosis by targeting multiple anti-apoptotic genes including XIAP, and may also suggest the therapeutic potential of miR-142-5p in ovarian cancer treatment.

Li X ，Chen W ，Jin Y ，Xue R ，Su J ，Mu Z ，Li J ，Jiang S ... -  《-》

MicroRNA-133b targets glutathione S-transferase π expression to increase ovarian cancer cell sensitivity to chemotherapy drugs.

Chen S ，Jiao JW ，Sun KX ，Zong ZH ，Zhao Y ... -  《Drug Design Development and Therapy》

Downregulation of miR-130a contributes to cisplatin resistance in ovarian cancer cells by targeting X-linked inhibitor of apoptosis (XIAP) directly.

Zhang X ，Huang L ，Zhao Y ，Tan W ... -  《-》