The Effect Of PDTC On Apoptosis And Expression Of Livin And Caspase-3 On Human Gastric Carcinoma SGC-7901 Cells

Background and Objective: Gastric cancer is one of the most commonmalignancies in our country. Most of patients with this disease arediagnosed in advanced stages, and lose the chance of surgical treatment.Despite recent progress in chemotherapy, the overall survival rate ofgastric cancer patients in advanced stages is still low. Apoptosisresistance of gastric cancer cell may be one of the "hot spot" of researchfields. Inhibitor of apoptosis protein(IAP) family may play a key role incausing apoptosis resistance and has become the focus of researchincreasingly. Livin is a novel inhibitor of apoptosis protein(IAP) familymember and overexpresses in most cancers. High expression of Livin candecrease sensitivity of chemotherapy. So it might elevate the effect ofcancer therapy to supress the expression of Livin and increase thesensitivity of cancer cell apoptosis.Nuclear factor kappa B(NF-κB), a transcription factor has been proved to play an important role in cell proliferation, apoptosis, cytokineproduction, and tumorigenesis. It is reported that NF-κB activation canup-regulate the expression of CIAP1 and CIAP2, but the relationshipbetween NF-κB activation and the expression of Livin is still not clear.Therefore, NF-KB blockage will be a new strategy in cancer therapy.The aim of this study was to detect the effect of PDTC, a selectiveinhibitor of NF-κB, on the cell survival and apoptosis of human gastriccarcinoma SGC-7901 cells, to analyze the expression of Livin andCaspase-3, and to explore the effect of Livin in the mechanism ofanti-NF-κB tumor cell apoptosis.Methods: After the treatment with PDTC on SGC-7901 cells, MTT assaywas used to observe growth inhibition of SGC-7901 cells; Flow cytometry(FCM) was used to detect the cell apoptosis; real time PCR and westernblot assay are applied to detect the expression of Livin and Caspase-3mRNA and protein, respectively.Results: There was a dose- and time-dependent inhibition of cellproliferation by PDTC(50～200mmol/L) at different timepoints(24h,48h,72h). As shown in FCM, after different concentrates ofPDTC for 48 h, theapoptotic rates were 9.37±0.23%, 16.58±1.26%,22.15±1.84% and 31.47±2.01%, respectively; and after 100mmol/L PDTCat different time points, they were 10.25±1.36%, 16.58±1.47% and23.66±1.95%, respectively; there were significant differences at the P＜0.001 level compared with other treatment and control groups. ThemRNA and protein expression of Livin were down-regulated, but those ofcaspase-3 were up-regulated by PDTC in a dose- and time-dependentmanner. Moreover, expression of Livin had a negative correlation withboth PDTC and the apoptosis rate of gastric carcinoma cell, which showeda dose- and time-dependent manner, and the correlation coefficients were84.5%, 95.1% and 84.1%, 87.6%, respectively. It also had a negativecorrelation with the expression of caspase-3, and the correlationcoefficients were 97.7%, 99.6%, respectively.Conclusion: (1) PDTC can induce apoptosis of human gastric carcinomaSGC-7901 cells, which shows that the blockage of NF-κB signalingpathway is very important in cancer therapy.(2) PDTC can down- regulate of Livin and up- regulate ofcaspase-3, which suggests that the expression of Livin is controlled byNF-κB activated state.