Rituximab-mediated Sensitiziation of B-NHL Cell Lines to Apoptosis Induced by Paclitaxel

Objective It is unsatisfied to the efficacy for patients with aggressive Non-Hodgkin's lymphoma(NHL) were treated by CHOP regimen (cyclophosphamide,doxorubicin,vincristine,and predisone).In this research,we studied the Rituximab-mediated sensitization of B-NHL cell lines to apoptosis induced by Paclitaxel and discussed their mechanism.Methods (1)Detection of inhibitive rate of cell proliferation by XTT assay: the cytotoxic effect of each treatment was calculated as the percentage of viability as compared to the untreated cells.The curves of cell inhibiting are draw by the concentration of drugs set as abscissa and the rates of inhibition as ordinate.There are two curves of inhibition: one for cytotoxic drug and another one for combination in rituximab with Paclitaxel.Shifting left of curve imply the synergistic effect,while shifting right of curve means the agonistic effect.(2)Western blot analysis of protein expression: The human burkitt’s lymphoma cell lines Daudi,Namalwa,Raji and Ramos cells were cultured in complete medium supplemented with either rituximab(20 μg/ml) or normal serum for ninety-six hours.At different times,the cells were harvested and the expression of anti-apoptosis protein Bcl-2 was analyzed by westblotting.Results (1)Inhibition of cell proliferation by either Paclitaxel alone or combination with rituximab was detected by XTT assay: rituxiamb could sensitize significantly the cytotoxicity of Paclitaxel in Daudi,Namalwa and Raji cell lines.(2)Analysis of Westblotting: Expression of Bcl-2 protein was down-regulated after treated by rituximab for 24 hours in Raji and Namalwa cell lines.Conclusion (1)Rituximab as a monomer could sensitize the cytotoxicity of Paclitaxel to the human lymphoma cell lines.(2)Expression of Bcl-2 in Raji and Namalwa cell lines was down-regulated after the cells were treated by rituximab for 24 hours.Down-regulation of Bcl-2 expression might be the one of mechanisms which the rituximab sensitized the cytotoxicity of cytotoxic drugs.