ABSTRACT
Although AKT1 (v-akt murine thymoma viral oncogene homologue 1) kinase is a central member of possibly the most frequently activated proliferation and survival pathway in cancer, mutation of AKT1 has not been widely reported. Here we report the identification of a somatic mutation in human breast, colorectal and ovarian cancers that results in a glutamic acid to lysine substitution at amino acid 17 (E17K) in the lipid-binding pocket of AKT1. Lys 17 alters the electrostatic interactions of the pocket and forms new hydrogen bonds with a phosphoinositide ligand. This mutation activates AKT1 by means of pathological localization to the plasma membrane, stimulates downstream signalling, transforms cells and induces leukaemia in mice. This mechanism indicates a direct role of AKT1 in human cancer, and adds to the known genetic alterations that promote oncogenesis through the phosphatidylinositol-3-OH kinase/AKT pathway. Furthermore, the E17K substitution decreases the sensitivity to an allosteric kinase inhibitor, so this mutation may have important clinical utility for AKT drug development.
Subject(s)
Blood Proteins/chemistry , Cell Transformation, Neoplastic/genetics , Mutation/genetics , Neoplasms/genetics , Phosphoproteins/chemistry , Proto-Oncogene Proteins c-akt/chemistry , Proto-Oncogene Proteins c-akt/genetics , Sequence Homology, Amino Acid , Animals , Breast Neoplasms/genetics , Colorectal Neoplasms/genetics , DNA Mutational Analysis , Enzyme Activation/genetics , Female , Humans , Leukemia/genetics , Mice , Models, Molecular , Neoplasms/pathology , Ovarian Neoplasms/genetics , Protein Structure, Tertiary/genetics , Protein Transport , Proto-Oncogene Proteins c-akt/metabolismABSTRACT
BACKGROUND: Fusion of the MOZ and TIF2 genes by an inv (8) (p11q13) translocation has been identified in patients with acute mixed-lineage leukemia. Characterization of the molecular structure of the MOZ-TIF2 fusion protein suggested that the fusion protein would effect on nuclear receptor signaling. RESULTS: A series of deletions from the N-terminus of the MOZ-TIF2 fusion protein demonstrated that the MOZ portion is essential for nuclear localization of the fusion protein. Transient expression of MOZ-TIF2 dramatically decreased both basal and estradiol inducible reporter gene activity in an estrogen receptor element (ERE) driven luciferase reporter system and decreased androgen-inducible reporter gene activity in an androgen receptor element (ARE) luciferase reporter system. Deletions in the MOZ portion of the MOZ-TIF2 fusion protein reduced the suppression in the ER reporter system. Stable expression of MOZ-TIF2 inhibited retinoic acid (RA) inducible endogenous CD11b and C/EBPbeta gene response. The suppression of the reporter systems was released with either a CID domain deletion or with mutations of leucine-rich repeats in the TIF2 portion of MOZ-TIF2. The co-expression of TIF2, but not CBP, with MOZ-TIF2 partially restored the inhibition of the reporter systems. In addition, analysis of protein interactions demonstrated MOZ-TIF2 interaction with the C-terminus of CBP through both the MOZ and TIF2 portions of the fusion protein. CONCLUSION: MOZ-TIF2 inhibited nuclear receptor-mediated gene response by aberrant recruitment of CBP and both the MOZ and TIF2 portions are required for this inhibition.
Subject(s)
Histone Acetyltransferases/metabolism , Nuclear Receptor Coactivator 2/metabolism , Oncogene Proteins, Fusion/genetics , Receptors, Cytoplasmic and Nuclear/genetics , Transcription, Genetic , Acute Disease , Blotting, Western , Carrier Proteins/genetics , Carrier Proteins/metabolism , Corticosterone , Genes, Reporter , Histone Acetyltransferases/genetics , Humans , Leukemia, Myeloid/genetics , Nuclear Receptor Coactivator 2/genetics , Oncogene Proteins, Fusion/chemistry , Receptors, Androgen/genetics , Receptors, Cytoplasmic and Nuclear/metabolism , Receptors, Estrogen/geneticsABSTRACT
The transforming growth factor-beta (TGF-beta) superfamily of ligands has a pivotal role in the regulation of a wide variety of physiological processes from development to pathogenesis. Since the discovery of the prototypic member, TGF-beta, almost 20 years ago, there have been tremendous advances in our understanding of the complex biology of this superfamily. Deregulation of TGF-beta has been implicated in the pathogenesis of a variety of diseases, including cancer and fibrosis. Here we present the rationale for evaluating TGF-beta signalling inhibitors as cancer therapeutics, the structures of small-molecule inhibitors that are in development and the targeted drug discovery model that is being applied to their development.