Background The multidrug resistance(MDR)associated with the expression of the mdr1 gene and its productP-glycoprotein is a major factor in the prognosis of hepatocellular carcinoma cell(HCC)patients treated withchemotherapy.Our study was to establish a stable HCC MDR cell line where a de novo acquisition of multidrugresistance specifically related to overexpression of a transgenic mdr1.Methods The 4.5-kb mdr1 cDNA obtained from the plasmid pHaMDR1-1 was cloned into the PCI-neo mammalianexpression vector,later was transferred by liposome to human hepatocarcinoma cell line HepG2.Then the transfectedHepG2 cells resisting G418 were clustered and cultured and the specific fragment of mdr1 cDNA,mRNA and theP-glycoprotein(Pgp)in these HepG2 cells were detected by PCR,RT-PCR and flow cytometry,respectively.Theaccumulation of the daunorubicin was determinated by flow cytometry simultaneously.The nude mice model of graftingtumour was established by injecting subcutaneously HepG2/mdr1 cells in the right axilla.When the tumour diameterreached 5 mm,adriamycin was injected into peritoneal cavity.The size and growth inhibition of tumour were evaluated.Results The mdr1 expression vector was constructed successfully and the MDR HCC line HepG2/mdr1 developed.The PCR analysis showed that the specific fragment of mdr1 cDNA in HepG2/mdr1 cells,but not in the control groupHepG2 cells.Furthermore,the content of the specific fragment of mdr1 mRNA and Pgp expression in HepG2/mdr1 cellswere(59.7±7.9)% and(12.28±2.09)%,respectively,compared with(16.9±3.2)% and(3.07±1.06)% in HepG2 cells.In the nude mice HCC model,the tumour genes of both groups were identified.After ADM therapy,the mean size ofHepG2 cell tumours was significantly smaller than HepG2/mdr1 cell tumours.Conclusion The approach using the transfer of mdr1 cDNA may be applicable to the development of MDRhepatocarcinoma cell line,whose MDR mechanism is known.This would provide the experimental basis of MDRresearch. Background The multidrug resistance (MDR) associated with the expression of the mdr1 gene and its product P-glycoprotein is a major factor in the prognosis of hepatocellular carcinoma cell (HCC) patients treated with chemotherapy. Your study was to establish a stable HCC MDR cell line where a de novo acquisition of multidrug resistance specific to overexpression of a transgenic mdr1.Methods The 4.5-kb mdr1 cDNA obtained from the plasmid pHaMDR1-1 was cloned into the PCI-neo mammalia expression vector, later was transferred by liposome to human hepatocarcinoma cell line HepG2 .Then the transfected HepG2 cells resisting G418 were clustered and cultured and the specific fragment of mdr1 cDNA, mRNA and the P-glycoprotein (Pgp) in these HepG2 cells were detected by PCR, RT-PCR and flow cytometry, respectively. The acumulation of the daunorubicin was determinated by flow cytometry simultaneously. The nude mice model of grafting tumor was established by injecting subcutaneously HepG2 / mdr1 cells in th e right axilla .When the tumor diameterreached 5 mm, adriamycin was injected into peritoneal cavity. size and growth inhibition of tumor were were evaluated. Results The mdr1 expression vector was constructed successfully and the MDR HCC line HepG2 / mdr1 developed.The PCR analysis showed that the specific fragment of mdr1 cDNA in HepG2 / mdr1 cells, but not in the control groupHepG2 cells. Frthermore, the content of the specific fragment of mdr1 mRNA and Pgp expression in HepG2 / mdr1 cellswere (59.7 ± 7.9)% and (12.28 ± 2.09)%, respectively, compared with (16.9 ± 3.2)% and (3.07 ± 1.06)% in HepG2 cells. In the nude mice HCC model, the tumor genes of both groups were identified. After ADM therapy, the mean size ofHepG2 cells tumours was significantly smaller than HepG2 / mdr1 cell tumours. Contact The approach using the transfer of mdr1 cDNA may be applicable to the development of MDRhepatocarcinoma cell line, whose MDR mechanism is known. This would provide the experimental basis of MDRresearch.