Radiosensitization effect of recombinant adenoviral-mediated PUMA gene on pancreatic carcinoma cells

Objective To study the effect of PUMA gene mediated by recombinant adenovirus vector combined with radiation on the pancreatic carcinoma. Methods The PANC-1 cells were infected with Ad-PUMA (MOI = 10, 50 and 100, respectively) for 48 h. The expression of PUMA mRNA and protein was detected by RT-PCR and Western blot, respectively. PANC-1 cells were divided into 4 groups: control group, transfection group, irradiation group and combined treatment group. The cell growth inhibition rate and apoptotic rate of PANC-1 cells were assessed by MTT assay and flow cytometry. Human pancreatic carcinomas were transplanted subcutaneously in nude mice, which were randomized into 4 groups: control group, transfection group, irradiation group and combined treatment group. Tumor growth rate and apoptotie index at different time points were recorded in 35 days. Results The expression of PUMA mRNA and protein was increased with the increase of MOI of Ad-PUMA, which was does-dependant (MOI = 10, mRNA = 0.46 ± 0.02, protein = 0. 75 ±0.09;MOI=50, mRNA= 1.12±0.09, protein = 1.01 ±0.18;MOI= 100, mRNA= 1.50±0.08, protein=1.80 ± 0.15 ;P < 0.05). The proliferation of PANC-1 cells was suppressed significantly when transfected by Ad-PUMA in a dose-dependent manner(r = -0.986 55), which was more significant combined with radiation (r = -0.971 26, P < 0.05). Meanwhile, the apoptotie rate was increased in the same manner [for pre- and post-irradiation,which was (45.4 ± 5.26) % and (73.2 ± 6.62) %, respectively, P < 0.05]. From 7 to 35 d after PUMA gene transfection and radiotherapy, the tumor growth was significantly slower than those of irradiation group, transfection group and control group [35 d after therapy, the volume of tumor was (19.82 ± 6.45)mm3 ,(39.5 ± 9.23)mm3 , (33.6 ±3 10.3)mm3 and (52.0 ± 11.43)mm3 , respectively, P < 0.05]. And the apoptotic index was increased in the same manner (AI = 0.43 ± 0.05, 0.29 ± 0.10, 0.24 ± 0.05 and 0.00 ± 0.00, respectively, P < 0.05). Conclusions Recombinant adenoviral-mediated PUMA gene combined with irradiation could increase the cell-killing effect on pancreatic carcinoma. It is better than that of either one kind of therapy. Key words: Recombinant adenovirus; p53 up-regulated modulator of apoptosis gene; Gene therapy; Radiotherapy; Pancreatic neoplasm