Impact of fragile histidine triad gene transfection on the proliferation and apoptosis of human colorectal cancer cell

Abstract

To investigate the effect of fragile histidine triad (FHIT) gene transfection on human colorectal cancer cell line SW480 through up-regulation of caspase-8 expression. The eukaryotic expression plasmid containing FHIT, pRc/CMV2-FHIT was prepared and purified, and then identified by restrictive enzyme digestion. pRc/CMV2-FHIT was transfected into SW480 cells, and positive cell clones (SW480-FHIT, study group) were selected and amplified. Empty plasmid-transfected SW480 cells(SW480-pRc/CMV2, negative control) and normal SW480 cells (bland control) were used as control. Methyl thiazolyl tetrazolium (MTT) assay was used to test the changes in the proliferation of SW480 cells. Cell-cycle kinetics and apoptosis were analyzed by flow cytometry (FCM). The changes of pro-caspase-8, caspase-8 mRNA and caspase-8 relative activity were analyzed by Western blot, semi-quantitative RT-PCR and colorimetric assay with pan labeled substrate, respectively. At 96 hours after transfection, cell inhibition rates of the study group and the negative control group were 71.7% and 16.9%. G0/G1 ratio was (63.2±3.5)% and (50.6±2.1)%, optical density of caspase-8 mRNA band 107 and 41, and relative activity of caspase-8 0.43 and 0.25, respectively. All the differences above were statistically significant (P<0.05). When FHIT inhibitor was added, the relative activity of caspase-8 decreased to 0.22, comparable to that in the control group. FHIT gene transfection can significantly inhibit the proliferation and induce G0/G1 arrest in human colon cancer cell line SW480. The mechanism is related to the up-regulation of caspase-8 expression.