RNAi silencing of polβgene partly reversing drug-resistance of esophageal cancer cells to cisplatin

Objective To silence polβgene by RNAi technique and to observe its effects on the drug-resistance of esophageal carcinoma cells to cisplatin(cDDP).Methods We constructed recombinant lentivirus containing siRNA targeting polβgenes.The two lentiviral vectors containing siRNA targeting the polβgene were designated as pRNAT-U6.2/Lenti-polβ1 and pRNAT-U6.2/Lenti-polβ2,and the negative control vector as pRNAT-U6.2/Lenti-polβC;they were used to infect EC9706/cDDP cells,which was resistant to cDDP.The expression of polβwas then examined by RT-PCR,Western blotting and immunofluorescence.MTT was used to observe the inhibitory effect of cDDP;the IC50of cDDP and resistance index(RI) were calculated.Results Both pRNAT-U6.2/Lenti-polβ1and pRNAT-U6.2/Lenti-polβ2down-regulated polβat mRNA and protein levels,with the effect of former being more prominent.Cisplatin inhibited EC9706/cDDP cell proliferation in a dosedependent manner.The IC50values of cDDP in cells infected with pRNAT-U6.2/Lenti-polβ1,pRNAT-U6.2/Lenti-polβC and untreated EC9706/cDDP were 55.71μg/mL,62.41μg/mL,and 63.11μg/mL,respectively,with the first one being significantly different from the latter two(P0.05);and the corresponding RI values were 13.9,15.5,and 15.7, respectively,also with the first one being significantly different from the latter two(P0.05).Results It is suggested that polβexpression is associated with cDDP resistance in EC9706/cDDP,and silencing polβby RNAi can partly reverse the drug resistance of EC9706/cDDP to cDDP.