Abstract
The serine/threonine kinase AKT is generally accepted as a promising anticancer therapeutic target. However, the relief of feedback inhibition and enhancement of other survival pathways often attenuate the anticancer effects of AKT inhibitors. These compensatory mechanisms are very complicated and remain poorly understood. In the present study, we found a novel 2-pyrimidyl-5-amidothiazole compound, DC120, as an ATP competitive AKT kinase inhibitor that suppressed proliferation and induced apoptosis in liver cancer cells both in vitro and in vivo. DC120 blocked the phosphorylation of downstream molecules in the AKT signal pathway in dose- and time-dependent manners both in vitro and in vivo. However, unexpectedly, DC120 activated mammalian target of rapamycin complex 1 (mTORC1) pathway that was suggested by increased phosphorylation of 70KD ribosomal protein S6 kinase (P70S6K) and eukaryotic translation initiation factor 4E binding protein 1 (4E-BP1). The activated mTORC1 signal was because of increase of intracellular Ca(2+) via Ca(2+)/calmodulin (CaM)/ signaling to human vacuolar protein sorting 34 (hVps34) upon AKT inhibition. Meanwhile, DC120 attenuated the inhibitory effect of AKT on CRAF by decreasing phosphorylation of CRAF at Ser259 and thus activated the mitogen-activated protein kinase (MAPK) pathway. The activation of the mTORC1 and MAPK pathways by DC120 was not mutually dependent, and the combination of DC120 with mTORC1 inhibitor and/or MEK inhibitor induced significant apoptosis and growth inhibition both in vitro and in vivo. Taken together, the combination of AKT, mTORC1 and/or MEK inhibitors would be a promising therapeutic strategy for liver cancer treatment.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adaptor Proteins, Signal Transducing / genetics
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Adaptor Proteins, Signal Transducing / metabolism
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Animals
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Antineoplastic Agents / pharmacology*
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Apoptosis / drug effects*
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Calcium Signaling / drug effects
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Calmodulin / metabolism
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Cell Cycle Proteins
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Cell Proliferation / drug effects
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Class III Phosphatidylinositol 3-Kinases / genetics
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Class III Phosphatidylinositol 3-Kinases / metabolism
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Dose-Response Relationship, Drug
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Feedback, Physiological
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Hep G2 Cells
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Humans
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Liver Neoplasms / drug therapy*
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Liver Neoplasms / enzymology
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Liver Neoplasms / genetics
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Liver Neoplasms / pathology
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MAP Kinase Signaling System / drug effects
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Mechanistic Target of Rapamycin Complex 1
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Mice, Nude
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Mitogen-Activated Protein Kinase Kinases / antagonists & inhibitors
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Mitogen-Activated Protein Kinase Kinases / metabolism
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Multiprotein Complexes / antagonists & inhibitors
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Multiprotein Complexes / genetics
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Multiprotein Complexes / metabolism
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Phosphoproteins / genetics
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Phosphoproteins / metabolism
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Phosphorylation
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Protein Kinase Inhibitors / pharmacology*
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Proto-Oncogene Proteins c-akt / antagonists & inhibitors*
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Proto-Oncogene Proteins c-akt / genetics
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Proto-Oncogene Proteins c-akt / metabolism
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Proto-Oncogene Proteins c-raf / metabolism
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Pyrimidines / pharmacology*
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RNA Interference
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Ribosomal Protein S6 Kinases, 70-kDa / metabolism
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TOR Serine-Threonine Kinases / antagonists & inhibitors
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TOR Serine-Threonine Kinases / genetics
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TOR Serine-Threonine Kinases / metabolism
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Thiazoles / pharmacology*
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Time Factors
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Transfection
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Tumor Burden / drug effects
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Xenograft Model Antitumor Assays
Substances
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Adaptor Proteins, Signal Transducing
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Antineoplastic Agents
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Calmodulin
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Cell Cycle Proteins
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EIF4EBP1 protein, human
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Multiprotein Complexes
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N-(1-amino-3-(2,4-dichlorophenyl)propan-2-yl)-2-(2-(methylamino)pyrimidin-4-yl)thiazole-5-carboxamide
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Phosphoproteins
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Protein Kinase Inhibitors
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Pyrimidines
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Thiazoles
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Class III Phosphatidylinositol 3-Kinases
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AKT1 protein, human
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Mechanistic Target of Rapamycin Complex 1
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Proto-Oncogene Proteins c-akt
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Proto-Oncogene Proteins c-raf
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Ribosomal Protein S6 Kinases, 70-kDa
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TOR Serine-Threonine Kinases
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Mitogen-Activated Protein Kinase Kinases