Abstract: Objective To investigate the effect of small interfering RNA (siRNA)-mediated COX-2 gene silencing in enhancing
the chemosensitivity of KB/VCR cell lines. Methods KB/VCR cells were trasnfected with COX-2 siRNA were examined for
expressions of COX-2 and MDR-1 mRNAs with RT-PCR and for Rho-123 accumulation using flow cytometry. MTT assay was
used to analyze the proliferation of the transfected KB/VCR cells. Results Compared with the negative and blank control
groups, COX-2 siRNA transfection resulted in significant growth inhibition of KB/VCR cells exposed to vincristine (P<0.01),
down-regulated the expressions of COX-2 and MDR-1 mRNAs, and obviously increased Rho-123 accumulation in KB/VCR
cells. Conclusion COX-2 gene silencing can enhance the chemosensitivity of KB/VCR cells to vincristine, the mechanism of
which may involve down-regulated MDR-1 gene expression and inhibition of P-glycoprotein activity.