| Objective :To clone human telomerase reverse transcriptase (hTERT) promoter and investigate its selective effect on breast cancer cells, ShRNA / hTERT expression vector targetes silencing resistant breast cancer cells (MCF-7/ADR) and observes changes of breast cancer resistance protein (BCRP) mRNA, its protein expression and change of drug resistance to doxorubicin in cell (MCF-7/ADR) and nude model organization.Methods:Plasmids (pGenesil-CMV-shRNA, pGenesil-hTERT-shRNA) were recombined and transfected into telomerase-negative and-positive cells, MCF-7/ADR breast cancer cells were inoculated with forelimb armpit of 50 nude mice, and 45 inoculation of animals were randomly divided into three groups, animal experiments were the following groups: control group, the recombinant plasmid pGenesil-CMV-shRNA group, the recombinant plasmid pGenesil-hTERT-shRNA group, hTERT promoter targeting was detected. RT-PCR, and Western-blot were applied to detect BCRP mRNA and protein of different groups of cells and organization.change of nude tumor volume ,MTT was applied to analyze drug sensitivity.Results:Highly visible fluorescent was seen in telomerase-positive cells, which was stronger than that of telomerase-negative cells. Nude mice model of human breast cancer was successfully constructed .The results of RT-PCR, and Western-blot showed that the mRNA and protein expression of BCRP were inhibited; nude mouse tumor volume was shrinked;the Plasmid pGenesil- hTERT-shRNA tumor inhibition rate was 68.5%;MTT results showed that the drug sensitivity to doxorubicin was significantly increased, which was of significant difference as compared with the control group (P <0 .05).Conclusion: ShRNA / hTERT expression vector can targeting silence BCRP gene and drug resistance to doxorubicin is reversed, which lays a solid experimental basis for the further development of tumor specific therapy in gene silencing.
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