The Synergistic Effect Of LDM And Rituximab On Human B Cell Lymphoma

Objective:Lidamycin is an antitumor antibiotics which has strong cytotoxicity against tumor cells. Rituximab is a monoclonal antibody and its major indication is B cell non Hodgkin’s lymphoma. Studies showed that both Rituximab combined with several chemotherapy drugs, and LDM combined with the other chemotherapy drugs have better joint effects. This study aimed to investigate the synergistic effect of LDM and Rituximab in human B cell lymphoma Ramos cells.Methods:In the model of human B cell lymphoma cell lines Raji and Ramos, Cell proliferation was measured using MTS assay, cell apoptosis was analyzed by Annexin V-FITC/PI assay, the expression of apoptosis related proteins was analyzed by Western Blot, and the in vivo lymphoma inhibition was verified using BALB/c mice inoculated via tail vein using Ramos cells which stably expressed pEGFP-N1 plasmid.Results:The results showed that, the inhibition of Rituximab on Raji and Ramos was found relatively low, and was not in dose-dependent mode. The synergistic effect of Rituximab and LDM administered simultaneously was not obvious. After the pretreatment with Rituximab for 48h, Rituximab and LDM showed significantly synergistic effects on cell proliferation. Flow cytometric analysis of cell cycle distribution showed that, after drugs treated 24h, the groups of LDM treatment had significantly higher inhibition of G2/M phase, and combined treatment groups had a lower inhibition of G2/M phase and a higher inhibition of G1/G0 phase. Cells in combined treatment groups had a higher apoptosis rate than LDM treatment groups. Compared with the LDM treatment groups, the expression of apoptosis-related proteins such as Cleaved Caspase-3, Cleaved Caspase-7, Cleaved Caspase-9 and Cleaved PARP in combined treatment groups increased, and expression of c-IAP-2 and Bcl-2 decreased. The result of in vivo experiment showed that, in the combined treatment group, the survival time of BALB/C mice was significantly longer than the mice in control group, and single drug treatment group, and the degree of tumor accumulate and metastasis to lymph nodes and spleen was lower.Conclusion:LDM combined with Rituximab treatment showed significant synergistic effect in human B cell lymphoma, it might be due to tumor resistance induced by LDM treatment was reversed by Rituximab through regulation of cell Bcl family and IAP family protein.