Effects of over-expression of homeobox gene caudal-related homeodomain transcription 2 on the multi-drug resistance of human gastric cancer cells

Objective To investigate the effects of over-expression of caudal-related homeodomain transcription 2 (Cdx2) on multi-drug resistance of the human gastric cell line SGC7901/DDP.Methods The human gastric cell line SGC7901/DDP was divided into the experimental group (cells were infected with Cdx2-recombi-nated lentiviral vector),the empty vector group (cells were infected with lentiviral vector) and the control group,respectively.The sensitivity of SGC7901/DDP to the chemotherapy agents was detected by the MTT method.The pump-out accumulation rates of adriamycin,cell cycle and apoptosis were detected by flow cytometry.The protein expressions of Cdx2 and multi-drug resistance gene 1 (MDR1) were analyzed by Western blot.All data were analyzed using the analysis of variance.Results The transfection efficiency was above 90％ after transfecting the SGC7901/DDP cells by lentiviral vector for 72 hours.The relative expression of Cdx2 protein in the experimental group was 0.37 ± 0.06,which was significantly higher than 0.12 ± 0.02 of the empty vector group and 0.11 ± 0.03 of the control group,with no significant difference between the 3 groups (F =82.37,P ＜ 0.05).The IC50 of SGC7901/DDP to adriamycin,5-fluorouracil and cisplatin in the experimental group were (1.10 ±0.08)mg/L,(4.81 ±0.12)mg/L and (3.81 ±0.15)mg/L,which were significantly higher than (0.59 ±0.05)mg/L,(3.7l ±0.14)mg/L and (2.20 ±0.15) mg/L of the empty vector group and (0.63 ±0.04) mg/L,(3.92 ±0.15) mg/L and (2.92 ± 0.11) mg/L of the control group (F =158.75,98.06,188.78,P ＜ 0.05).The pumpout accumulation rate of adriamycin in the experimental group was 18.20％ ± 0.12％,which was significantly higher than 7.22％ ± 0.09％ of the empty vector group and 8.79％ ± 0.11％ of the control group (F =146.31,P ＜ 0.05).The proportion of cells in the G1 phase in the experimental group was 52.2％ ± 4.4％,which was significantly lower than 62.0％ ± 5.0％ of the empty vector group and 67.8％ ± 3.3％ of the control group.The proportion of cells in the S phase in the experimental group was 40.4％ ± 1.5％,which was significantly higher than 25.6％±2.0％ of the empty vector group and 21.8％ ± 1.3％ of the control group.There were significant differences in the proportion of cells in the G1 phase and S phase between the 3 groups (F =17.08,236.83,P ＜0.05).The cell apoptotic rate of the experimental group was 7.6％ ± 1.3％,which was significantly lower than 11.1％±1.1％ of the empty vector group and 10.8％±1.0％ of the control group (F=16.29,P＜0.05).The relative protein expression of MDR1 in the experimental group was 1.85 ± 0.18,which was significantly higher than 1.12 ± 0.08 in the empty vector group and 1.02 ± 0.09 of the control group (F =76.22,P ＜ 0.05).Conclusion Over-expression of Cdx2 gene could decrease the sensitivity of gastric cell line SGC7901/DDP to chemotherapy agents as well as the intracellular accumulation of the agents,and it can also enhance the multi-drug resistance of the gastric cell line SGC7901/DDP. Key words: Gastric neoplasms;  Caudal-related homeodomain transcription 2;  Multi-drug resistance