目的研究人结肠癌耐药细胞系的耐药机制．方法采用抗Ｐ糖蛋白单抗ＪＳＢ１和ＭＲＫ１６以免疫细胞化学染色法（ＡＢＣ）检测ＨＣＴＶ２０００及亲本ＨＣＴ８细胞的Ｐ糖蛋白表达；提取两种细胞的ＤＮＡ和ＲＮＡ，与探针ＰＨＤＲ５Ａ杂交检测耐药基因ｍｄｒ１的表达和扩增；ＭＴＴ法测定ＶＣＲ对两种细胞的细胞毒作用．结果细胞系ＨＣＴＶ２０００对抗Ｐ糖蛋白单抗呈阳性反应，编码Ｐ糖蛋白的多药耐药基因ｍｄｒ１过度表达，但未见扩增或重排．异博定（１０μｇ／ｍｌ）使ＨＣＴｖ２０００细胞内３ＨＶＣＲ蓄积增加将近４倍，对ＶＣＲ的敏感性提高８４倍，可部分逆转耐药．结论多药耐药基因ｍｄｒ１ｍＲＮＡ过度表达是ＨＣＴＶ２０００细胞耐药的重要原因，但还有其他机制参与 Objective To study the resistance mechanism of human colon cancer drug-resistant cell lines. Methods The expression of Pglycoprotein in HCTV2000 and parental HCT8 cells was detected by immunocytochemical staining (ABC) using anti-Pglycoprotein monoclonal antibodies JSB1 and MRK16; the DNA and RNA of the two cells were extracted. The probe PHDR5A hybridization was used to detect the expression and amplification of mdr1 gene; MTT assay was used to determine the cytotoxic effect of VCR on both cells. Results The cell line HCTV2000 reacted positively against the P glycoprotein monoclonal antibody, and the multidrug resistance gene mdr1 encoding P glycoprotein was over-expressed, but no amplification or rearrangement was observed. Isobrindidine (10μg/ml) increased the accumulation of 3H-VCR in HCTv2000 cells by nearly 4-fold and the sensitivity to VCR by 84-fold, partially reversing drug resistance. Conclusion The overexpression of multidrug resistance gene mdr1 mRNA is an important cause of drug resistance in HCTV2000 cells, but there are other mechanisms involved