AIM:To observe the reversal effects of wide-type p53 geneon multi-drug resistance to 5-FU (LOVO/5-FU).METHODS:After treatment with Ad-p53,LOVO/5-FUsensitivity to 5-Fu was investigated using tetrazolium dyeassay.Multidrug resistance gene-1 (MDR1) gene expressionwas assayed by semi-quantitative reverse transcription-polymerase chain reaction and the expression of p53 proteinwas examined by Western blotting.RESULTS:The reversal activity after treatment with wide-type p53 gene was increased up to 4.982 fold at 48 h.Theexpression of MDR1 gene decreased significantly aftertreatment with wide-type p53 gene,and the expression ofp53 protein lasted for about 5 d,with a peak at 48 h,andbegan to decrease at 72 h.CONCLUSION:Wide-type p53 gene has a remarkablereversal activity for the high expression of MDR1 gene incolorectal cancers.The reversal effects seem to be in a timedependent manner.It might have good prospects in clinicalapplication. AIM: To observe the reversal effects of wide-type p53 geneon multi-drug resistance to 5-FU (LOVO / 5-FU). METHODS: After treatment with Ad-p53, LOVO / 5-FUsensitivity to 5- tetrazolium dyeassay.Multidrug resistance gene-1 (MDR1) gene expression was assayed by semi-quantitative reverse transcription-polymerase chain reaction and the expression of p53 protein was examined by Western blotting .RESULTS: The reversal activity after treatment with wide-type p53 gene was increased up to 4.982 fold at 48 h. The expression of MDR1 gene decreased significantly aftertreatment with wide-type p53 gene, and the expression of p53 protein lasted for about 5 d, with a peak at 48 h, and began to decrease at 72 h. -type p53 gene has a remarkablereversal activity for the high expression of MDR1 gene incolorectal cancers. the reversal effects seem to be in a time dependent manner. It might have good prospects in clinicalapplication.