Inhibitory effect of bcl-XL antisense oligodeoxynucleotides on the proliferation of colon cancer cells and the growth of human colon cancer xenografts in nude mice

Abstract

Objective To investigate the effect of bcl-XL antisense oligonucleotide transfection on the proliferation of colon cancer cells and the growth of human colon cancer xenografts in nude mice. Methods A long-term SW620 single cell suspension was prepared for subcutaneous injection in nude mice. Nude mice were randomly divided into 3 groups: control group, N-ODN group and antisense oligonucleotide group (n=5), with an average of 50 mm3. The antisense oligonucleotide group and N-ODN group were injected with 2 ml/kg antisense oligonucleotide or N-ODN, and the control group was injected with equal amount of normal saline. At 16th day after the operation, the tumor cells were taken out, and some tumor tissues were extracted. RNA and protein were extracted. The cationic liposome mediated transfection of antisense oligonucleotide, real-time quantitative polymerase chain reaction (Real-time PCR), Western blotting, methyl thiazol tetrazolium (MTT) method and TdT-mediated dUTP nick end labeling (TUNEL) method were applied to observe the effects of bcl-XL antisense oligonucleotide on the proliferation and apoptosis of colorectal cancer cells in vivo and the growth of human colon cancer xenografts. Results (1) The inhibition rate of cell proliferation activity was gradually increased with the increase of antisense oligonucleotide concentration. When the concentration was over 200 nmol/L, the inhibition rate of cell proliferation was significantly decreased with the difference being statistically significant (t=2.418, 1.531 and 1.838, P=0.003, 0.016 and 0.011). (2) The relative expression levels in the control group, blank control group, N-ODN group and mRNA antisense oligonucleotides group were 0.96±0.25, 0.97±0.48, 0.78±0.32 and 0.41±0.13, the inhibition rate was 0.00%, -6.25%, 18.75% and 57.29%, respectively. There was significant difference between antisense oligonucleotide group and control group, blank control group or N-ODN group (P=0.025). (3) Compared with the control group, there was no significant change in the blank control group; the N-ODN group was slightly lower than that in the control group; the antisense oligonucleotide group was significantly lower (P=0.017). (4) The positive rates of cells in control group, blank control group, N-ODN group and antisense oligonucleotide group were 3.7%, 5.0%, 7.0% and 35.0%, respectively. By statistical analysis, antisense oligonucleotide group and cell control group, blank control group and N-ODN group, the difference was statistically significant (χ2=181.880, P=0.000); cells in the control group, N-ODN group and control group comparison between 22 blank, there was no statistically significant difference (χ2=1.410, P=0.084). (5) There was no significant difference in tumor volume between first groups (P=0.162). On the sixth day, there was significant difference between the antisense oligonucleotide group and the control group (t=2.410, P=0.027). On the eleventh and the 16 day, there was significant difference between the two groups in (P=0.028, 0.016). (6) The expression of bcl-XL gene in the tumor tissues of the 3 groups of nude mice was significantly decreased after antisense oligonucleotide treatment, but the expression of antisense oligonucleotide group was significantly decreased, while the expression of N-ODN in the control group and the control group did not change significantly. Conclusion bcl-XL antisense oligonucleotides can effectively inhibit the proliferation of colon cancer cells and the growth of human colon cancer xenografts in nude mice. To reduce the expression of bcl-XL by antisense oligonucleotides, and to provide the experimental basis for gene therapy of colon cancer. Key words: Colon cancer; Oligonucleotides; Bcl-XL; Proliferation