Combined targeting of AKT and mTOR using MK-2206 and RAD001 is synergistic in the treatment of cholangiocarcinoma
ABSTRACT Cholangiocarcinoma (CCA) is a rare, but devastating disease arising from the epithelium of intra- and extrahepatic bile ducts. There are neither effective systemic therapies nor satisfying treatment options for inoperable CCA. Histopathological and biochemical studies of CCA show frequent dysregulation of the PI3K/AKT/mTOR pathway. Therefore, we investigated the efficacy of the mTOR inhibitor RAD001 and the impact of AKT signaling following mTOR inhibition in the treatment of CCA. RAD001 significantly inhibits proliferation of CCA cell lines, however, a concentration-dependent and isoform specific feedback activation of the three AKT isoforms (AKT1, AKT2, AKT3) was observed after mTOR inhibition. Since activation of AKT might limit the RAD001-mediated anti-tumor effect, the efficacy of combined mTOR and AKT inhibition was investigated using the allosteric AKT inhibitor MK-2206. Our results show that inhibition of AKT potentiates the efficacy of mTOR inhibition both in vitro and in a xenograft mouse model in vivo. Mechanistically, the anti-proliferative effect of the pan-AKT inhibitor MK2206 in the CCA cell line TFK-1 was due to inhibition of AKT1 and AKT2, because knockdown of either AKT1 or AKT2, but not AKT3, showed a synergistic reduction of cell proliferation in combination with mTOR treatment. Finally, by using an AKT isoform specific in vitro kinase assay, enzymatic activity of each of the three AKT isoforms was detected in all tissue samples from CCA patients, analyzed. In summary, our preclinical data suggest that combined targeting of mTOR and AKT using RAD001 and MK-2206 might be a new, effective strategy for the treatment of CCA. © 2013 Wiley Periodicals, Inc.
SourceAvailable from: Muthusamy Kunnimalaiyaan[Show abstract] [Hide abstract]
ABSTRACT: Cholangiocarcinoma (CCA) is an aggressive disease with limited effective treatment options. The PI3K/Akt/mTOR pathway represents an attractive therapeutic target due to its frequent dysregulation in CCA. MK2206, an allosteric Akt inhibitor, has been shown to reduce cellular proliferation in other cancers. We hypothesized that MK2206 mediated inhibition of Akt would impact CCA cellular viability. Post treatment with MK2206 (0-2 μM), cellular viability was assessed in two human CCA cell lines-CCLP-1 and SG231-using an MTT assay. Lysates from the MK2206 treated CCA cells were then examined for apoptotic marker expression levels using Western blot analysis. Additionally, the effect on cellular proliferation of MK2206 treatment on survivin depleted cells was determined. CCLP-1 and SG231 viability was significantly reduced at MK2206 concentrations of 0.5, 1, and 2 μM by approximately 44%, 53%, and 64% (CCLP-1; p = 0.01) and 32%, 32%, and 42% (SG231; p < 0.00005) respectively. Western analysis revealed a decrease in AKT(Ser473), while AKT(Thr308) expression was unchanged. In addition, cleaved PARP as well as survivin expression increased while pro-caspase 3 and 9 levels decreased with treatment. Depletion of survivin in CCLP-1 cells resulted in apoptosis as evidenced by increased cleaved PARP. In addition, survivin siRNA further enhanced the antitumor activity of MK2206. This study demonstrates that by blocking phosphorylation of Akt at serine473, CCA cellular growth is reduced. The growth suppression appears to be mediated via apoptosis. Importantly, combination of survivin siRNA transfection and MK2206 treatment significantly decreased cell viability.Cancer Cell International 12/2015; 15(1):13. DOI:10.1186/s12935-015-0161-9 · 1.99 Impact Factor
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ABSTRACT: Until today, there is no systemic treatment available for advanced cholangiocarcinoma (CCA). Recent studies have shown a frequent upregulation of the PI3K-AKT-mTOR and RAF-MEK-ERK pathways in this type of cancer. However, considering their high extend of redundancy and cross-talk, targeting only one pathway is likely to result in therapy failure and emergence of resistances. To provide a rationale for treatment of CCA with inhibitors of these respective pathways, we analyzed the effects of AKT inhibitor MK-2206, MEK inhibitor AZD6244 (ARRY-142886) and mTOR kinase inhibitor AZD8055 on three CCA cell lines in vitro, concerning proliferation, cell signaling and apoptosis. Furthermore, AZD6244 resistant cell lines have been generated to investigate, how their response may be affected by prolonged treatment with only a single inhibitor. Our data demonstrates that co-targeting of both, the PI3K/AKT/mTOR and RAF-MEK-ERK pathway, as well as vertical targeting of AKT and mTOR results in strong synergistic effects on proliferation and cell survival with combination indices below 0.3. Mechanistically, the combinatorial treatment with MK-2206 in addition to AZD8055 is necessary because AKT kinase activity was quickly restored after mTOR kinase inhibition. Interestingly, acquired MEK inhibitor resistance to AZD6244 was reversed by combined treatment with AZD6244 and either MK-2206 or AZD8055. Our data suggest that a combination of inhibitors targeting those respective pathways may be a viable approach for future application in patients with cholangiocarcinoma. Implications: AKT, mTOR and MEK are promising targets for a combinatorial treatment of cholangiocarcinoma cells even after acquisition of MEK inhibitor resistance.Investigational New Drugs 08/2014; DOI:10.1007/s10637-014-0149-7 · 2.93 Impact Factor
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ABSTRACT: Background Hepatocellular carcinoma (HCC) is commonly diagnosed at an advanced stage and has limited effective treatment options. The aberrant regulation of the phosphoinositide 3-kinase (PI3K)/Akt pathway in HCC makes it an attractive therapeutic target. The effect of MK2206, a novel, allosteric Akt inhibitor, on HCC cells is not yet fully understood. We hypothesized that inhibition of Akt by MK2206 would impact cellular viability. Materials and Methods Human Huh7, Hep3B, and HepG2 cell lines were treated with 0-2μM of MK2206 for 96 hours. Cell viability was determined by using MTT assay. Western blot analysis was used to examine the expression level of various protein markers to assess the mechanism of drug action and proliferation inhibition. Results MTT assay showed a reduction in cellular viability by ≥ 55% for all cell lines (control v. 2μM MK2206; p<0.001). Western blot analysis revealed reduction in the level of phosphorylated AKT-Ser473 with no change in AKT-Thr308 expression— confirming the specificity of MK2206. There was an observed reduction in caspase-9 and survivin. Importantly, there were increases in p21 and p27 along with decreased cyclinD1 expression post-treatment. Conclusions This study demonstrates the antitumor activity of MK2206 in HCC cells. The observed reduction in survivin and procaspase-9 suggests that MK2206 induces apoptosis. However, HCC proliferation is also halted via induction of cell cycle arrest as indicated by the increase in p21 and p27 expression and decrease in cyclinD1. Importantly, the concentration needed to achieve growth inhibition in HCC is lower than that needed for other cancer types.Journal of Surgical Research 02/2014; 191(2). DOI:10.1016/j.jss.2014.05.083 · 2.12 Impact Factor