[Expression of Runt-related Transcription Factor 3 in Human Colon Cancer Cell Line HCT-116 Resistant to 5-Fluorouracil and the Mechanism of Drug Resistance].

Objective To establish a human colon cancer cell line HCT-116/5-FU resistant to 5-fluorouracil(5-FU)and explore the relationship between runt-related transcription factor 3(RUNX3)and drug resistance of colorectal cancer.Methods The human colon cancer cell line HCT-116/5-FU with resistance to 5-FU was established by low concentration gradient increment combined with high-dose intermittent shock.CCK-8 method was used to determine the half maximal inhibitory concentration(IC50)of 5-FU on the parent line HCT-116 and drug-resistant line HCT-116/5-FU.The cell growth curve was established for the calculation of population doubling time(TD).The mRNA levels and protein levels of RUNX3,P-glycoprotein(P-gp),multidrug resistance-associated protein 1(MRP1),and lung resistance-related protein(LRP)in HCT-116 and HCT-116/5-FU cells were determined by qRT-PCR and Western blotting,respectively.The RUNX3 expression in HCT-116 cells was knocked down by siRNA technique,and the cells were divided into RUNX3 knockdown groups(si-RUNX3-1 group and si-RUNX3-2 group)and negative control group(si-NC group).The knockdown efficiency was verified by qRT-PCR at the mRNA level and Western blotting at the protein level.The IC50 in si-RUNX3 groups and si-NC group was determined with CCK-8 method,and the expression of P-gp,MRP1,and LRP in the two groups was detected by Western blotting.Results A stable human colon cancer drug-resistant cell line HCT-116/5-FU was successfully constructed.HCT-116/5-FU showed the TD 1.38 times as long as that of HCT-116(P=0.002)and changed morphology.The mRNA level of RUNX3 in HCT-116/5-FU cells was significantly lower than that in HCT-116 cells(P=0.048),and those of P-gp(P=0.008),MRP1(P=0.001),and LRP(P=0.001)showed the opposite trend.The protein level of RUNX3 in HCT-116/5-FU cells was significantly lower than that in HCT-116(P<0.001),and those of P-gp,MRP1,and LRP presented the opposite trend(all P<0.001).The HCT-116 cell model with low expression of RUNX3 was successfully established.The mRNA level of RUNX3 had no significant difference between si-RUNX3-1 group and si-NC group(P=0.064),while the level in si-RUNX3-2 group was significantly lower than that in si-NC group(P=0.034).The protein levels of RUNX3 in si-RUNX3-1 group and si-RUNX3-2 group were lower than that in si-NC group(both P<0.001).The results demonstrated higher knocking efficiency in si-RUNX3-2 group,which was thus selected to complete the follow-up test.The IC50 of si-RUNX3 group was significantly higher than that of si-NC group(P<0.001),which indicated that the down-regulated expression of RUNX3 could reduce the sensitivity of HCT-116 cells to 5-FU.The relative protein levels of P-gp,MRP1,and LRP in si-RUNX3 group were significantly higher than those in si-NC group(all P<0.001).Conclusion The down-regulation of RUNX3 expression can reduce the sensitivity of HCT-116 cells to 5-FU,which is considered to be related to the up-regulated expression of P-gp,MRP1,and LRP.