Suppression of ATR reverses the cisplatin resistance in ovarian cancer SKOV3 cells / 中华肿瘤杂志

<p><b>OBJECTIVE</b>To explore the effect of ataxia telangiectasia mutated and RAD3 related protein (ATR) expression and ATR kinase activity on the sensitivity to cisplatin in ovarian cancer SKOV3 cells.</p><p><b>METHODS</b>SiRNA targeting ATR was transfected into SKOV3 cells for 48 h to reduce the ATR protein level, and ATR kinase inhibitor VE-821 was used for 12 h to inhibit the ATR pathway activity. The alteration of cell viability was examined by CCk-8 assay. Expression levels of ATR, p-ATR and γ-H2AX proteins were detected by Western blot. The DNA double strand breaks (DSB) marker γ-H2AX and homologous recombination repair key protein RAD51 and their co-localization in the cells were examined under the confocal microscope. The status of DNA double strand breaks (DSB) in single cells was visualized by alkaline comet assay. Finally, the cell cycle distribution was assessed using flow cytometry.</p><p><b>RESULTS</b>DDP caused evident DNA double strands breaks and activated ATR kinase pathway. ATR-siRNA notably reduced ATR protein level, the 48 h IC(50) value of DDP was 72.12 µmol/L and 41.25 µmol/L, respectively, in the NC-siRNA and ATR-siRNA groups (P < 0.05). Confocal microscopic assay presented decreased recruitment of RAD51 at the DSB loci and comet assay showed enhanced DSB in the cells after ATR knocking down. After the inhibition of ATR kinase by VE-821, the 48 h IC(50) value of DDP was 75.32 µmol/L and 45.64 µmol/L, respectively, in the DMSO and VE-821 groups (P < 0.05 for both), confocal microscopic assay demonstrated reduced RAD51 recruitment, and comet assay showed increased DSB in cells after ATR kinase inhibition. Flow cytometry showed that percentage of cells distributed in G(0)/G(1), S and G(2)/M phases was 71.2%, 13.4% and 15.4%, repectively, after 40 µmol/L DDP treatment for 24 h. Compared with that of control group (G(0)/G(1): 54.2%, S: 21.3% and G(2)/M: 24.4%), DDP induced G(0)/G(1) phase arrest. DDP intervention resulted in the cell cycle status (G(0)/G(1): 43.2%, S: 20.4%, G(2)/M: 36.4%) in the ATR-siRNA group and (G(0)/G(1): 40.2%, S: 22.5%, G(2)/M: 37.3%) in the VE-821 group, indicating that the inhibition of ATR or ATR kinase could abrogate the effect of G(0)/G(1) phase arrest induced by DDP.</p><p><b>CONCLUSIONS</b>Suppression of ATR can affect the homologous recombination repair in ovarian cancer cells, leading to accumulation of DNA double strand breaks in the cell nuclei as well as reduction of DDP-caused G(0)/G(1) phase arrest, finally enhances the sensitivity to cisplatin in the ovarian cancer SKOV3 cells.</p>

MYC suppresses ovarian cancer cell adhesion and invasion ability through downregulation of human integrinβ1 / 实用医学杂志

Objective To explore the influence of MYC expression level on ovarian cancer cells adhesion and invasion ability,and the involvement of the integrinβ1 in the adhesion and invasion control. Methods Comparative study was done to analyze the relationship between the mRNA level of MYC and ITGB1 among sixty cell lines from the NCI-60 cells bank; Western blot was performed to demonstrate the correlation of MYC and ITGB1 protein level in ovarian cancer cell lines;Immunohistochemistry was adopted to compare the expression level of MYC and ITGB1 in paired primary and metastatic ovarian cancer tissue. Furthermore ,we employed in vitro adhesion test to detect the alteration of ovarian cancer cell adhesion ability to ECM molecular like fibronectin ,collagen I and laminin after fluctuation of MYC and ITGB1 expression; Transwell assay was applied to check the invasion ability variation with the disturbance of MYC and ITGB1 level. Results The mRNA levels of MYC and ITGB1 were dramatically inverse-correlated in NCI-60 cells bank(P<0.01);The protein levels of MYC and ITGB1 in ovarian cancer cell lines were also negative correlated; The primary ovarian cancer tissue showed lower expression of ITGB1 and higher expression of MYC,while the matched metastasis displayed the opposite outcome;Ovarian cancer cells reduced adhesive and invasive capacity in case of ITGB1 being down-regulated ,however, the adhesive and metastatic ability improved tremendously with elevation of ITGB1;Promoted adhesion and invasion ability and rise of ITGB1 expression were observed after downregulation of MYC,meanwhile,and inhibition of ITGB1 reversed the increasement of adhesion and invasion ability. Conclusions MYC,inversely-correlated with ITGB1 in ovarian cancer cells,inhibited ovarian cancer cells adhesion and invasion. Inhibition of MYC could lead to enhanced adhesion and invasion ability of ovarian cancer cells.