Effects of gambogic acid on the activation of caspase-3 and downregulation of SIRT1 in RPMI-8226 multiple myeloma cells via the accumulation of ROS

Department of Hematology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, P.R. China.
Oncology letters (Impact Factor: 1.55). 05/2012; 3(5):1159-1165. DOI: 10.3892/ol.2012.634
Source: PubMed


Multiple myeloma (MM) is the second most commonly diagnosed hematologic malignancy. Although new drugs, including bortezomib and lenalidomide, have improved the treatment landscape for MM patients, MM remains incurable. Therefore, screening for novel anti-myeloma drugs is necessary. Gambogic acid (GA), the main active ingredient of gamboges secreted from the Garcinia hanburryi tree, has been reported to exhibit potent anticancer activity in certain solid tumors and hematological malignancies, while there are few studies that are available concerning its effects on MM cells. In the present study, we investigated the anticancer activity of GA on the MM RPMI-8226 cells and further studied the underlying mechanisms by which GA affected the cells. RPMI-8226 cells were cultured and the effect of GA on cell proliferation was analyzed using MTT assay. Hoechst 33258 staining was used to visualize nuclear fragmentation, and reactive oxygen species (ROS) levels were detected. GA was found to have a significant, dose-dependent effect on growth inhibition and apoptosis induction in RPMI-8226 cells. This activity is associated with the accumulation of ROS, which contributes to the activation of caspase-3 and the cleavage of poly (ADP-ribose) polymerase (PARP), accompanied with apoptosis in RPMI-8226 cells treated with GA. Mammalian SIRT1, as the closest homolog of the yeast Sir2, was extensively involved in regulating cell processes, including cell senescence, aging and neuronal protection, as well as having anti-apoptotic properties. Moreover, SIRT1 overexpression has been shown to protect cancer cells from chemotherapy and ionizing radiation. In the present study, we demonstrated that GA has the potential to downregulate the expression of SIRT1 via ROS accumulation. In conclusion, our study found that GA is able to induce apoptosis in RPMI-8226 cells via ROS accumulation followed by caspase-3 activation, PARP cleavage and SIRT1 downregulation. These results suggest that GA may have the potential to not only induce apoptosis in MM cells, but also to decrease the relapse rate of MM.

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    • "In the present study, 2DE-based proteomics in combination with bioinformatics analyses revealed that 22% of the proteins altered upon GA treatment were involved in redox homeostasis. Recently, GA has been reported to induce ROS accumulation in human hepatoma SMMC-7721 cells, the ovarian cancer cell line (SKOV-3) and multiple myeloma RPMI-8226 cells, contributing to apoptosis by triggering the mitochondrial signaling pathway and activating caspase-3 [40], [41], [42]. However, the role of GA-induced ROS in autophagy has not yet been reported. "
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    • "Our study also showed that ApoE-/-mice livers have lower expressions of SIRT1, suggesting that this protein is involved in an accelerated aging process. These results agree with data of Yang et al. (2012) who demonstrated that SIRT-1 expression could be downregulated via ROS generation. The nuclear size of hepatocytes increase with age in ApoE-/-mice. "
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