Bufalin enhances the anti-proliferative effect of sorafenib on human hepatocellular carcinoma cells through downregulation of ERK
ABSTRACT The purpose of this study was to investigate the effect of bufalin on the anti-proliferative activity of sorafenib in the human hepatocellular carcinoma (HCC) cell lines PLC/PRF/5 and Hep G-2 and to determine the relevant molecular mechanism. Concurrent treatment with sorafenib and bufalin at a fixed ratio (25:1) for 48 h resulted in synergistic growth inhibition in HCC cell lines as determined by CCK-8 cell viability assays. Exposure of both PLC/PRF/5 and Hep G-2 cells to this combination of sorafenib (6.25 μM) and bufalin (50 nM) resulted in noticeable increases in apoptotic cell death, as evidenced by the disruption of mitochondria, compared to treatment with either agent alone. Although both sorafenib (6.25 μM) and bufalin (250 nM) alone inhibited the phosphorylation of ERK, the reduction in pERK was more pronounced in the cells treated with a combination of bufalin (50 nM) and sorafenib (250 nM). Furthermore, the inhibitory effect of bufalin on pERK was blocked by the PI3kinase inhibitor LY294002, suggesting that the reduction in pERK induced by bufalin might be mediated by AKT in these two HCC cell lines. Taken together, the results of our study suggest that bufalin enhances the anti-cancer effects of sorafenib on PLC/PRF/5 and Hep G-2 by contributing to the downregulation of ERK.
- SourceAvailable from: Zhenggang Ren
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- "Signaling through RAF/MEK/ERK plays a crucial role in cell proliferation, differentiation, malignant transformation, and apoptosis [19,20]. It has been thoroughly demonstrated that sorafenib exhibits remarkable antitumor activity in HCC in vitro and in vivo, through targeting the RAF/MEK/EKR cascade [21,22]. Our results agree well with these reports. "
ABSTRACT: Recently, a phase II clinical trial in hepatocellular carcinoma (HCC) has suggested that the combination of sorafenib and 5-fluorouracil (5-FU) is feasible and side effects are manageable. However, preclinical experimental data explaining the interaction mechanism(s) are lacking. Our objective is to investigate the anticancer efficacy and mechanism of combined sorafenib and 5-FU therapy in vitro in HCC cell lines MHCC97H and SMMC-7721. Drug effects on cell proliferation were evaluated by cell viability assays. Combined-effects analyses were conducted according to the median-effect principle. Cell cycle distribution was measured by flow cytometry. Expression levels of proteins related to the RAF/MEK/ERK and STAT3 pathways and to cell cycle progression (cyclin D1) were determined by western blot analysis. Sorafenib and 5-FU alone or in combination showed significant efficacy in inhibiting cell proliferation in both cell lines tested. However, a schedule-dependent combined effect, associated with the order of compound treatments, was observed. Efficacy was synergistic with 5-FU pretreatment followed by sorafenib, but it was antagonist with the reverse treatment order. Sorafenib pretreatment resulted in a significant increase in the half inhibitory concentration (IC50) of 5-FU in both cell lines. Sorafenib induced G1-phase arrest and significantly decreased the proportion of cells in S phase when administrated alone or followed by 5-FU. The RAF/MEK/ERK and STAT3 pathways were blocked and cyclin D1 expression was down regulated significantly in both cell lines by sorafenib; whereas, the kinase pathways were hardly affected by 5-FU, and cyclin D1 expression was up regulated. Antitumor activity of sorafenib and 5-FU, alone or in combination, is seen in HCC cell lines. The nature of the combined effects, however, depends on the particular cell line and treatment order of the two compounds. Sorafenib appears to reduce sensitivity to 5-FU through down regulation of cyclin D1 expression by inhibiting RAF/MEK/ERK and STAT3 signaling, resulting in G1-phase arrest and reduction of the S-phase cell subpopulation when 5-FU is administrated after sorafenib, in which situation, combination treatment of the two agents results in antagonism; on the other hand, when sorafenib is administrated afterward, it can continue to work since it is not cell cycle specific, as a result, combination treatment of the two agents shows an additive-to-synergistic effect.BMC Cancer 07/2013; 13(1):363. DOI:10.1186/1471-2407-13-363 · 3.36 Impact Factor
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ABSTRACT: Cardiac glycosides (CGs) are compounds used for the treatment of cardiac failure which also display strong anti-cancer activity inducing impairment of cell proliferation or activation of cell death whether by apoptosis or autophagy. Despite the fact that the sodium/potassium (Na(+)/K(+))-ATPase is a well-known target of CGs, its involvement in the anti-cancer effect of these compounds remains to be validated. Importantly, related intracellular sensor(s)/transducer(s) needs further characterization. We will discuss here key mechanisms activated by CGs including their ability to modulate the cell cycle and to regulate the expression of anti-apoptotic Bcl-2 family members, two so far marginally investigated events.Mitochondrion 06/2012; 13(3). DOI:10.1016/j.mito.2012.06.003 · 3.25 Impact Factor
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ABSTRACT: Cardiac glycosides represent group of compounds isolated from plants and some animals. They have been using in the therapy of heart failure for many years. In spite of the fact that cytotoxic effect of many cardiac glycosides has been demonstrated. The mechanism of the cytotoxic action is very complicated and complex, where Na+/K+-ATPase plays crucial role. On the other hand, Na+/K+-ATPase is regulated by many endogenous factors including hormones or FXYD proteins, which role in the regulation of cell cycle is intensively studied. This review focuses the role of Na+/K+-ATPase in the regulation of cell growth, cell cycle and cell proliferation and involvement of cardiac glycosides in the regulation of Na+/K+-ATPase. Cytotoxic effect of cardiac glycosides is discussed in the connection with possible apoptotic mechanisms induced by these compounds. Novel strategies in cancer therapy based on the cardiac glycosides as well as possibilities in the overcoming multidrug resistance by cardiac glycosides are discussed too. The goal of this review is to present cardiac glycosides as not only pharmaceuticals used in heart failure, but also as potent cytotoxic agents with possible involvement in cancer treatment.Anti-cancer agents in medicinal chemistry 03/2013; 13(7). DOI:10.2174/18715206113139990304 · 2.47 Impact Factor