[Regulatory effect of small interfering RNA targeting multidrug resistant protein 1 on chemosensitivity of human multiforme glioblastoma cell line BT325].

BACKGROUND & OBJECTIVE: Multidrug resistance is a major reason of failure of chemotherapy for glioma. Overexpression of P-glycoprotein (P-gp), encoded by multidrug resistant protein 1 (MDR1) gene, is one of the key factors. This study was to explore the regulatory effect of small interfering RNA (siRNA) targeting MDR1 on chemosensitivity of human multiforme glioblastoma cell line BT325. METHODS: MDR1 siRNAs containing sequences of 3,051-3,069 (MDR1 A group), 502-520 (MDR1 B group), and 1,534-1,552 (MDR1 C group) were designed, and transfected into BT325 cells. Positive clones were screened with puromycin. The expression of MDR1 was measured by reverse transcription-polymerase chain reaction (RT-PCR); the expression of P-gp was detected by immunohistochemistry and flow cytometry (FCM). Drug sensitivity assay was performed in the transfected cells. RESULTS: BT325 cells proliferated exponentially after MDR1 siRNA transfection. After transfection of MDR1 siRNAs, the expression of MDR1 mRNA was significantly lower in MDR1 A, B, and C groups than in control group (0.18+/-0.05, 0.30+/-0.09, and 0.36+/-0.13 vs. 0.76+/-0.06, P<0.001); the positive rate of P-gp was decreased from 85.73% to 1.44%; the 50% inhibitory concentrations (IC(50)) of doxorubicin and vincristine to BT325 cells were decreased markedly; the G0/G1 phase proportions of MDR1 A, B, and C groups were increased by 13.55%, 14.35%, and 1.46% of control, respectively (P<0.05). CONCLUSION: MDR1 siRNA may modulate multidrug resistance through down-regulating the expression of MDR1 gene, enhancing the chemosensitivity of glioma, and inducing cell apoptosis.