PO-451 Novel combination of tanshinone I and dexamethasone induces apoptosis in myeloma cells by modulating ERK/p38/JNK/NF-kB signalling pathway

Abstract

IntroductionMultiple myeloma (MM) is a B-cells malignancy involving excessive proliferation and accumulation of abnormal plasma cells dwelling in the bone marrow (BM). Multiple primary and secondary genetic mutations regulating major signalling pathways get deregulated thereby giving plasma cells abnormal and malignant phenotype. Despite several advances in treatment of myeloma, majority of patients relapse after successful remission of the disease. Therefore, this maiden attempt aims to reveal the therapeutic potential of TanshinoneI (TanI) in combination with dexamethasone (Dexa) on myeloma cells.Material and methodsIn this in-vitro study, inhibitory concentration (IC50) concentration of TanI and Dexa on both cells was determined using MTT dye. To assess the anti-proliferative and apoptosis potential of these drug combinations, cell-cycle and apoptosis assay were performed using propidium iodide (PI) and annexin-V/PI, caspase-3/7 activity and JC1 dye. After drug treatment, western blotting were performed to unveil the pathways involving in mediating the effects of drugs. Statistical analysis was done using GraphPad 5.0 prism software.Results and discussionsTanI inhibited cell proliferation effectively and efficiently in both myeloma cells in a dose dependant manner. RPMI8226 cells gave IC50 of 2.0 uM while U266 cells showed IC50 at 2.5 uM dose only. Dexa showed no significant cytotoxity on both myeloma cells. Further, TanI significantly induced cell apoptosis in both myeloma cells while combination of both TanI and Dexa significantly potentiate cell death in both myeloma cells. Additionally, combination treatment demonstrated drastic increase in the caspase-3/7 activity and loss of MMP compared to controls. Furthermore, western blotting results showed that TanI and Dexa increased the expression of Bax and PUMA with simultaneous decrease in BCL-2 protein levels. Lastly, apoptosis inducing effects of TanI alone or in combination with dexa was demonstrated mainly through modulating the ERK/p38/JNK/NF-kB pathways.ConclusionIn nutshell, this maiden study provided initial evidences of TanI as novel anticancer agent alone or in combination with standard chemotherapeutic agent Dexa. Further, novel combination of TanI and Dexa was more potent in inducing apoptosis and chemo-sensitising myeloma cells than single drug treatment regime. Lastly the involvement of ERK/p38/JNK/NF-kB in myeloma suggested the pathway targeted by TanI which opens up the prospect of its validation in pre-clinical setting in future.