The Effects And Mechanism Of Curcumin In Combination With Bortezomib On The Proliferation And Apoptosis Of Multiple Myeloma Cell Line

【Background】Multiple myeloma (MM), an incurable disease originated from B cell terminal differentiation, is a hematologic malignancy which is characterized by clonal proliferation of malignant plasma cells. Direct adhesive interactions between MM and bone marrow microenvironment contribute to the growth, proliferation and chemoresistance of MM cells, as well as bone disease. Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) is a transcription factor closely linked to development of MM. Bortezomib, a first-line treatment for MM patients, has been shown to possess significant clinically activity. Though initial overall response rates to bortezomib are promising, the vast majority of patients develop resistance to the drug over time. Curcumin, a yellow pigment in turmeric, has been shown to inhibit the activation of nuclear NF-κB and exhibit antitumor activities as well. Some research in vitro has shown that curcumin suppresses the proliferation of many kinds of human MM cell lines. Considering the adverse effects and toxic effects of chemotherapeutic agents as well as the non-toxicity of curcumin, curcumin has been shown to have great promise as a therapeutic agent in combination with bortezomib.【Objectives】To investigate the effects of curcumin in combination with bortezomib on the proliferation and apoptosis of human MM cell line H929 in vitro and further to explore the mechanisms.【Methods】MTT assay was applied to detect the inhibitory effects of curcumin and bortezomib either alone or combined at different concentration, and flow cytometry was also used to analyze the apoptosis rate. After treatment with curcumin or bortezomib, the morphology of cell line H929 in each group were observed by light microscope. Additionally, RT-PCR was used to analyze the mRNA expression of gene bcl-2/bax and CyclinD1. Immunofluorescence staining was performed to show the localization changes of NF-κB p65 in different groups.【Results】Curcumin and bortezomib, used both respectively and conjointly, could inhibit the proliferation of MM cell line H929 in dose-dependent manner. Meanwhile in combinative group, they worked synergistically. There were significant differences in the morphology of cell line H929 between single group and combinative, as well as curcumin and bortezomib group. A much higher apoptosis rate was observed in combinative group by flow cytometry than that in single drug group or control (P<0.05). And RT-PCR showed, in contrast with curcumin or bortezomib group, there was a decrease of bcl-2, CyclinD1 mRNA expression but an increase of bax in combinative group (P<0.05). The expression of NF-κB P65 in nucleus was downregulated in either each group, whereas, it was cytoplasmic-positive in combinative group. 【Conclusions】The combination of curcumin and bortezomib is much more effective on the inhibiting proliferation and promoting apoptosis of H929 cell line, which may possibly be functioned by inhibiting the transcription of NF-κB and apoptosis-related genes.