Bufalin enhances the anti-proliferative effect of sorafenib on human hepatocellular carcinoma cells through downregulation of ERK

Department of Integrative Oncology, Fudan University Shanghai Cancer Center, Shanghai, China.
Molecular Biology Reports (Impact Factor: 2.02). 05/2011; 39(2):1683-9. DOI: 10.1007/s11033-011-0908-x
Source: PubMed


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.

6 Reads
  • Source
    • "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. "
    [Show abstract] [Hide abstract]
    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.
    Full-text · Article · Jul 2013 · BMC Cancer
  • [Show abstract] [Hide abstract]
    ABSTRACT: Hepatocellular carcinoma (HCC) is the fifth most common cancer and it is the third leading cause of cancer-related deaths worldwide. Once diagnosed with the disease, only 30-40% of patients are deemed eligible for curative intention with treatment modalities including surgical resection, liver transplantation, and chemoembolization. Eventually, most patients will receive some forms of chemotherapy in hope of prolonging life. Sorafenib is the first molecular inhibitor to be approved by the FDA for the treatment of advanced HCC. It is a tyrosine kinase inhibitor, targeting multiple molecular pathways. Prior to the arrival of sorafenib, doxorubicin was routinely used as a single drug for advanced HCC, but has shown inefficacy, with a response rate of about 15-20%. Other chemotherapy agents, such as epirubicin, cisplatin, 5-fluorouracil, etoposide and their combinations, demonstrate even lower efficacy. While being considered an advance over conventional chemotherapy, sorafenib only improves life expectancy approximately by 3 months over placebo. With that in mind, continuous efforts have been put into finding new targets and molecular pathways for possible new drug development. In this article, we summarize the current literature over the past year on chemotherapy treatment of advanced HCC.
    No preview · Article · Apr 2012 · Anticancer research
  • Source
    [Show abstract] [Hide abstract]
    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.
    Full-text · Article · Jun 2012 · Mitochondrion
Show more