OSTP Enhances Paclitaxel-induced Apoptosis On The Ovarian Cancer A2780Cells

Objective: It shows that the ovarian cancer specific targeting peptide (OSTP) hasbeen firstly screened and identified in the preliminary work. The purpose of this studyis to investigate further the effect of OSTP combined with paclitaxel on the growthand apoptosis of ovarian cancer A2780cells. For the study and development of OSTP,it would provide experimental basis for exploring and developing OSTP which is as atargeted chemotherapy sensitization agent to the treatment of ovarian cancer.Methods: Ovarian cancer A2780cells were cultured in vitro and then randomlydivided into four groups: control groups (included1640and DMSO), OSTP group,paclitaxel group, OSTP combined with paclitaxel group; MTT-assay was used tomeasure the inhibition ability of OSTP on A2780cells proliferation; Annexin-V-FITCand PI double staining were used to label A2780cells and FCM was used to detect thecell apoptosis; Phosphorylation protein chip was used to detect the phosphorylatedlevel changes of the kinase in the signal pathway, and we further studied on the levelof the phosphorylated protein in the signal pathway by western blot experiments.Results: The result showed that different concentrations of OSTP(0.01、0.1、1、10、100umol/L) had an inhibited effect on the ovarian cancer A2780cells by MTT-assay,and the inhibition rates were27.36%,32.68%,36.08%,40.77%,57.32%; Comparedwith control group, the difference was statistically significant (P<0.01); The IC50value of OSTP was78.18umol/L. The result of FCM showed that the apoptosis ratesof different concentrations of OSTP (20,40,80,160,320umol/L) on A2780cells were7.88%,8.35%,8.73%,9.39%and10.68%, and compared with control group, thedifference was statistically significant (P<0.01). Our findings suggested that OSTPcould induce cell apoptosis, but the effect of apoptosis was not very strong. Thecombined groups, that was to add respectively OSTP80umol/L0h,3h,6h,12h, thenplus paclitaxel10umol/L and had an effect on ovarian cancer A2780cells for48h. The apoptosis rates were respectively39.40%,53.09%,48.18%and45.62%; They werehigher than OSTP and paclitaxel monotherapy and even their added value (P<0.001).It was suggested that OSTP could enhance paclitaxel-induced apoptosis on theovarian cancer A2780cells. Phosphorylation protein chip was used to detectphosphorylated level of protein when OSTP combined with paclitaxel induced theapoptosis of ovarian cancer A2780cells. The result was screened42differentphosphorylation sites and31differential proteins. There was11kinds of proteins withexpressing the high phosphorylated level and23kinds of proteins with expressing thelow level; Western blot was further performed to study on the level of two differentialand phosphorylated proteins (such as FoxO1/3/4,14-3-3zeta/delta) in the PI3K/Aktsignaling pathway. Results showed that compared with control groups, FoxO1/3/4phosphorylated protein level in both OSTP and paclitaxel group werereduced(P<0.01); Compared with both OSTP and paclitaxel group, FoxO1/3/4phosphorylated protein level in combined group were decreased (P<0.01); Meanwhile,compared with control groups,14-3-3zeta/delta phosphorylated protein level in bothOSTP and paclitaxel group were reduced (P<0.01); Compared with both OSTP andpaclitaxel group,14-3-3zeta/delta phosphorylated protein level in combined groupwas decreased (P<0.01).Conclusion:1. OSTP could enhance paclitaxel-induced apoptosis on the ovarian cancerA2780cells.2. The mechanism may be related to the decreased expression of FoxO1/3/4and14-3-3zeta/delta phosphorylation proteins, which were the key proteins inPI3K/Akt signal pathway.