Effect of gene GSTP1 silencing via shRNA transfection on androgen independent prostate cancer cell line Du145

Abstract

To design short hairpin RNA (shRNA) interference sequence to silence glutathione S-transferase P1 (GSTP1) gene of androgen independent prostate cancer cell line DU145, and to explore its effect on proliferation and sensitivity to chemotherapeutics. The target sequence was picked up to form the shRNA, and the 3 shRNA expression vectors were shRNA255, shRNA554 and shRNA593. The DNA template was cloned to plasmid pGPU6/GFP/Neo. The shRNA was identified by enzyme digesting and gene sequencing. The screening experiment was done to pick up the shRNA expression vector with the highest transfection ratio and best gene silencing results. DU145 cells were divided into a blank plasmid group and a shRNA transfected group. According to the chemotherapeutics the DU145 cells were divided into a fluorouracil (FU) group and a paclitaxel (PA) group, and the 2 groups were subdivided into 4 subsets according to the chemotherapeutic concentrations (FU: 30, 60, 120, and 240 μg/mL; PA: 0.2, 2, 10, and 20 μg/mL), meanwhile a blank control group was included respectively. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay was used to evaluate the proliferation after the transfection. MTT and terminal de-oxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay were used to detect the inhibition effect of different concentrations of 5-FU or PA on the proliferation and induction of apoptosis of DU145. The transfection ratio of the 3 shRNA expression vectors (shRNA255, shRNA554, and shRNA593) was (63.30±1.04)%, (76.20±0.68)%, and (72.70±0.33)%, and the transfection ratio of shRNA554 was the highest. there was significant difference among the above 3 shRNA expression vectors (P<0.01). After the transfection, the mRNA was 128.31±2.50, 43.24±4.30 and 85.62±6.30, the GSTP1 protein was 163.92±12.40, 65.38±9.30 and 114.25±16.70. After the transfection of shRNA554, the mRNA and protein of GSTP1 were the lowest level. there was significant difference among the above 3 shRNA expression vector (P<0.01). MTT analysis showed that before the transfection, the survival ratio of cells under different concentrations of FU (30, 60, 120, and 240 μg/mL) was (95.60±2.11)%, (90.20±0.86)%, (83.10±3.12)% and (74.60±1.32)%; however after the transfection, the survival ratio of cells was (91.30±1.43)%, (84.60±2.13)%, (73.20±1.52)%, and (65.5±0.942)%. TUNEL assay showed that before the transfection, the apoptosis ratio of cells under different concentrations of FU (30, 60, 120, and 240 μg/mL) was (5.50±0.88)%, (10.20±1.64)%, (15.20±2.39)%, and (25.10±2.59)%; however after the transfection, the apoptosis ratio of cells was (10.8±0.62)%, (15.7±1.32)%, (20.4±1.89)%, and (34.9±2.54)%. After the transfection, the cell survival ratio decreased under the same concentration of FU, and the apoptosis ratio increased, with statistical significance (both P<0.01). MTT analysis showed that before the transfection, the survival ratio of cells under different concentrations of PA (0.2, 2, 10, and 20 μg/mL) was (98.50±2.34)%, (95.20±1.32)%, (89.40±0.68)%, and (82.70±1.73)%; after the transfection the survival ratio of cells was (94.20±0.78)%, (86.50±2.13)%, (78.70±1.34)%, and (70.10±0.76)%. TUNEL assay showed that before the transfection, the apoptosis ratio of cells under different concentrations of PA (0.2, 2, 10, and 20 μg/mL) were (2.40±1.07)%, (5.20±1.33)%, (10.50±2.41)%, (20.70±1.92)%; after the transfection the apoptosis ratio of cells was (5.46±2.13)%, (13.80±1.24)%, (21.20±2.39)%, and (29.20±2.21)%. After the transfection, the cell survival ratio decreased under the same PA concentration, and the apoptosis ratio increased, with statistical significance (both P<0.01). gene GSTP1 silence via shRNA transfection to androgen independent prostate cancer cell line DU145 can inhibit its proliferation in time dependent manner, and induce apoptosis and raise its sensitivity to chemotherapeutics.