Yunping Lu

RNA interference against HPV16 E7 oncogene leads to viral E6 and E7 suppression in cervical cancer cells and apoptosis via upregulation of Rb and p53

The simultaneous expression of human papillomavirus type 16 (HPV16) E6 and E7 oncogenes is pivotal for malignant transformation and maintenance of malignant phenotypes. Silencing these oncogenes is considered to be applicable in molecular therapies of human cervical cancer. However, it remains to be determined whether HPV16 E6 and E7 could be both silenced to obtain most efficient antitumor activity by using RNA interference (RNAi) technology. Herein, we designed a small interfering RNA (siRNA) targeting HPV16-E7 region to degrade either E6, or truncated E6 (E6*) and E7 mRNAs and to simultaneously knockdown both E6 and E7 expression. Firstly, the sequence targeting HPV16-E7 region was inserted into the shRNA packing vector pSIREN-DNR, yielding pSIREN-16E7 to stably express corresponding shRNA. HPV16-transformed SiHa and CaSki cells were used as a model system; RT-PCR, Western Blotting, MTT assay, TUNEL staining, Annexin V apoptosis assay and flow cytometry were applied to examine the effects of pSIREN-16E7. Our results indicated that HPV16-E7 specific shRNA (16E7-shRNA) induced selective degradation of E6 and E7 mRNAs and proteins. E6 silencing induced accumulation of cellular p53 and p21. In contrast, E7 silencing induced hypophosphorylation of retinoblastoma (Rb) protein. The loss of E6 and E7 reduced cell growth and ultimately resulted in massive apoptotic cell death selectively in HPV-positive cancer cells, compared with the HPV-negative ones. We demonstrated that 16E7-shRNA can induce simultaneous E6 and E7 suppression and lead to striking apoptosis in HPV16-related cancer cells by activating cellular p53, p21 and Rb. Therefore, RNAi using E7 shRNA may have the gene-specific therapy potential for HPV16-related cancers.

Activation of fibronectin/PI-3K/Akt2 leads to chemoresistance to docetaxel by regulating survivin protein expression in ovarian and breast cancer cells

The purpose of this study was to investigate the possible role of PI-3K/Akt2 pathway in docetaxel-induced apoptosis. Here we showed that transfection of full-length Akt2 into breast and ovarian cancer cells could provoke Akt phosphorylation and induce an enhanced resistance to docetaxel. FN adhesion promoted Akt phosphorylation in highly metastatic cancer cells A2780 and MDAMB231, and further brought on significant protection for tumor cells against docetaxel-induced apoptosis. Inhibition of Akt2 activity by co-transfection with two shRNA vectors targeting the same Akt2 mRNA or simply by administration with PI 3-Kinase inhibitor Ly294002 counteracted the ability of FN to protect cells from undergoing apoptosis induced by docetaxel. We further showed that Akt2 activation protected against docetaxel-induced apoptosis by regulating survivin levels in a PI 3-Kinase-dependent manner. We conclude that FN/PI-3K/Akt2 pathway might play an important role in inducing resistance to docetaxel in breast and ovarian cancer cells. Our results therefore indicate that the activation of Akt2, promoted by FN attachment, might be critical in determining whether cells survive or undergo apoptosis. Targeting the PI-3K/Akt2 pathway might be a promising strategy for enhancing sensitivity to docetaxel in breast or ovarian cancer.

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.SummaryChemotherapy 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.

Effect of tumor suppressor gene PTEN on the resistance to cisplatin in human ovarian cancer cell lines and related mechanisms

PURPOSE The aim of this study was to explore role of PTEN gene in chemosensitivity to cisplatin in human ovarian cancer cells and related mechanisms. METHOD A PTEN-targeted short hairpin RNA (shRNA) expression vector and a wild-type sense PTEN plasmid were constructed, human ovarian cisplatin-sensitive cancer cell line OV2008 and its resistant variant C13 * cells were transfected with PTEN shRNA or wild-type PTEN plasmid, respectively, and cells were then treated with cisplatin. Next, AKT activity was regulated with co-transfection of antisense or sense AKT plasmid in OV2008 /PTENshRNA cells or C13 */p-PTEN cells, respectively. Effects of transfection of above vectors on cell growth, apoptosis and expression of PTEN and AKT were evaluated. RESULTS Expression of PTEN in OV2008 cells was significantly higher than that in C13 * cells. Transfection of PTEN shRNA into OV2008 cells remarkably down-regulated expression of PTEN and up-regulated expression of phospho-AKT protein, with transfected cells being resistant to cisplatin. Overexpression of PTEN by transfection with sense PTEN obviously enhanced cisplatin-induced apoptosis of C13 * cells. Furthermore, decreased AKT activity could increase cisplatin-induced apoptosis in OV2008/PTENshRNA cells; while, transfection of pcDNA3.1-AKT plasmid into C13 */p-PTEN cells resulted in increased activity of AKT, with cisplatin-induced apoptosis being inhibited significantly. CONCLUSIONS PTEN might reverse chemoresistance to cisplatin in human ovarian cancer cells through inactivation of the PI3K/AKT cell survival pathway and may serve as a potential molecular target for the treatment of chemoresistant ovarian cancer.

Expression Patterns and Regulatory Functions of MicroRNAs During the Initiation of Primordial Follicle Development in the Neonatal Mouse Ovary

ABSTRACT The initiation of primordial follicle development is essential for female fertility, but the signals that trigger this process are poorly understood. Given the potentially important roles of microRNAs (miRNAs) in the ovary, we aimed to study the expression patterns and regulatory functions of miRNAs during the initiation of primordial follicle development. Expression patterns of miRNA in the neonatal mouse ovary were profiled by microarray, and 24 miRNAs whose abundances differed significantly between ovaries from 3- and 5-day-old mice were identified. Pathway enrichment analysis revealed that 48 signal transduction pathways are modulated by the up-regulated miRNAs and 29 pathways are modulated by the down-regulated miRNAs (P-value and false discovery rate < 0.001). A miRNA-mRNA regulatory network was established for TGF-beta signaling pathway-related genes. Among the miRNAs involved in this pathway, miR-145 was chosen for further analysis. Down-regulation of miR-145 using an antagomir (AT) decreased the proportion and number of the primordial follicles and increased that of the growing follicles in the cultured ovaries (P < 0.05). The mean oocyte diameter in the primordial follicles was significantly greater in the AT group relative to the AT-negative control group (P < 0.05), whereas the mean oocyte diameter in growing follicles was smaller in the AT group than in the AT-negative control group. In addition, we confirmed that miR-145 targets Tgfbr2. The miR-145 AT caused an increase in TGFBR2 expression and activation of Smad signaling but did not affect the p38 MAPK or JNK pathway. These data suggest that miRNAs and the signaling pathways they modulate are involved in the initiation of primordial follicle development, and miR-145 targets Tgfbr2 to regulate the initiation of primordial follicle development and maintain primordial follicle quiescence.

The potassium ion channel opener NS1619 inhibits proliferation and induces apoptosis in A2780 ovarian cancer cells

Diverse types of voltage-gated potassium (K+) channels have been shown to be involved in regulation of cell proliferation. The maxi-conductance Ca2+-activated K+ channels (BK channels) may play an important role in the progression of human cancer. To explore the role of BK channels in regulation of apoptosis in human ovarian cancer cells, the effects of the specific BK channel activator NS1619 on induction of apoptosis in A2780 cells were observed. Following treatment with NS1619, cell proliferation was measured by MTT assay. Apoptosis of A2780 cells pretreated with NS1619 was detected by agarose gel electrophoresis of cellular DNA and flow cytometry. Our data demonstrate that NS1619 inhibits the proliferation of A2780 cells in a dosage and time dependent manner IC50=31.1 microM, for 48 h pretreatment and induces apoptosis. Western blot analyses showed that the anti-proliferation effect of NS1619 was associated with increased expression of p53, p21, and Bax. These results indicate that BK channels play an important role in regulating proliferation of human ovarian cancer cells and may induce apoptosis through induction of p21(Cip1) expression in a p53-dependent manner.

Abrogation of constitutive Stat3 activity circumvents cisplatin resistant ovarian cancer

The aim of the present study was to investigate the role of Stat3 in cisplatin resistant ovarian cancer. It was first demonstrated that higher activated Stat3 was detected in cisplatin-resistant ovarian cancer cell lines. To provide evidence that supported the hypothesis that phosphorylated-Stat3 expression may promote cisplatin resistance, ectopic Stat3 was expressed by IL-6 stimulation that partially abrogates Stat3, as opposed to the knock-down of Stat3 by specific siRNA that restores cisplatin sensitivity against ovarian cancer cells. This hypothesis was further confirmed by clinical tumor specimens of ovarian cancer obtained from patients with cisplatin-resistance. Based on these premises, Stattic, an effective small molecular inhibitor of Stat3, was used to inhibit Stat3 activation. The data presented here show that Stattic restored the sensitivity to cisplatin in chemoresistant ovarian cancer by significant reductions in the expression of the anti-apoptosis protein Bcl-2, Bcl-XL, Survivin protein and phosphorylated-Akt levels. Consistent with these observations, this experiment demonstrated the first evidence of Stattic circumvented cisplatin resistance of orthotopic xenograft ovarian cancer in vivo. Altogether, these findings emphasize the importance of Stat3 in cisplatin resistance in ovarian cancer and provide a further impetus to clinically evaluate biological modifiers that may circumvent cisplatin resistance in patients with chemoresistant ovarian cancer.

Peroxiredoxin 2 Inhibits Granulosa Cell Apoptosis During Follicle Atresia Through the NFKB Pathway in Mice

Peroxiredoxin 2 (PRDX2) has been known to act as an antioxidant enzyme whose main function is H2O2 reduction in cells. We aimed to study the expression patterns of PRDX2 in mouse ovaries and explore the function of this protein in apoptosis of granulosa cells (GCs). We found that the expression of the PRDX2 protein in atretic follicle GCs was markedly higher than in healthy follicle GCs. In vitro, the transfection of siRNA targeting the Prdx2 gene inhibited the proliferation and induced the apoptosis of primary cultured GCs. Furthermore, suppression of PRDX2 resulted in the augmentation of endogenous H2O2, and the ability to eliminate the exogenous H2O2 was attenuated. The expression of PRDX2 and nuclear factor kappa-light-chain-enhancer of activated B cells (NFKB), whose activity was inhibited by binding to IKB, increased in GCs treated with various concentrations of H2O2 for 30 min. However, no significant change in cytoplasmic IKB expression was observed. At 2 h after treatment with H2O2, nuclear NFKB expression level was reduced, cytoplasmic IKB expression was increased, and PRDX2 expression was unchanged. Silencing of the Prdx2 gene caused early changes in NFKB and IKB expression in the primary cultured GCs compared to that in control cells. Taken together, these data suggest that PRDX2 plays an important role in inhibiting apoptosis in GCs and that PRDX2 actions may be related to the expression of NFKB and IKB.

microRNA‑199a is able to reverse cisplatin resistance in human ovarian cancer cells through the inhibition of mammalian target of rapamycin

microRNAs (miRNAs/miRs) may have a crucial function in tumor metastasis through the regulation of a plethora of signaling pathways. Increasing evidence has shown that miR-199a is important in regulating the tumor metastasis of ovarian cancer, although the precise biological function of miR-199a is unclear at present. In the current study, it was observed that the expression levels of miR-199a were higher in OV2008 cells compared with C13* cells. However, lower levels of mammalian target of rapamycin (mTOR) protein were detected by western blotting in the OV2008 cells compared with the C13* cells. The miR-199a levels were increased in the C13* cells using miR-199a mimics and the mTOR levels were observed to decrease. This may have resulted in a reversal of cisplatin resistance in the C13* cells. To test this hypothesis, the Renilla luciferase reporter gene system was used to analyze the mTOR levels. The results indicated that the expression levels of mTOR were significantly blocked by the increased miR-199a levels. When the miR-199a inhibitor was applied to decrease the miR-199a levels, it was observed that the mTOR expression levels were increased, while cisplatin-induced apoptosis was decreased in the OV2008 cells. The study concludes that miR-199a is able to reverse cisplatin resistance in human ovarian cancer cells through the inhibition of mTOR and that mTOR may be the target of miR-199a during this process.

Noscapine sensitizes chemoresistant ovarian cancer cells to cisplatin through inhibition of HIF-1α

Hypoxia-inducible factor 1 alpha (HIF-1α) is closely related with chemoresistance of solid tumors. The purpose of this study was to investigate the ability of noscapine to inhibit HIF-1α and sensitize ovarian cancer cells to cisplatin (DDP) under hypoxic conditions. Herein, we report that noscapine sensitized cobalt-induced chemoresistant ovarian cancer cells to DDP-induced apoptosis and inhibition of cell proliferation. Noscapine also promoted proteasome-mediated degradation of cobalt-stabilized HIF-1α protein, with subsequent inhibition of HIF-1 transcriptional activity. These data establish noscapine as a small molecule inhibitor of HIF-1α and provide an evidence for its combination with DDP in combating ovarian cancer chemoresistance.