Abstract
Phosphotidylinositol-3-kinase (PI3K) signaling is altered in the majority of human cancers. To gain insight into the roles of members of this pathway in growth regulation, we inactivated AKT1, AKT2, or PDPK1 genes by targeted homologous recombination in human colon cancer cell lines. Knockout of either AKT1 or AKT2 had minimum effects on cell growth or downstream signaling. In contrast, knockout of both AKT1 and AKT2 resulted in markedly reduced proliferation in vitro when growth factors were limiting and severely affected experimental metastasis in mice. Unexpectedly, AKT1 and AKT2 appeared to regulate growth through FOXO proteins, but not through either GSK3beta or mTOR. In contrast, inactivation of PDPK1 affected GSK3beta and mTOR activation. These findings show that the PI3K signaling pathway is wired differently in human cancer cells than in other cell types or organisms, which has important implications for the design and testing of drugs that target this pathway.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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3-Phosphoinositide-Dependent Protein Kinases
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Animals
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Apoptosis
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Blotting, Western
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Cell Proliferation*
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Colorectal Neoplasms / genetics
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Colorectal Neoplasms / metabolism*
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Colorectal Neoplasms / pathology
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Forkhead Box Protein O1
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Forkhead Transcription Factors / genetics
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Forkhead Transcription Factors / metabolism
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Gene Silencing
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Glycogen Synthase Kinase 3 / genetics
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Glycogen Synthase Kinase 3 / metabolism
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Glycogen Synthase Kinase 3 beta
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HCT116 Cells
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Humans
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Interleukin Receptor Common gamma Subunit / deficiency
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Interleukin Receptor Common gamma Subunit / genetics
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Intracellular Signaling Peptides and Proteins / genetics
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Intracellular Signaling Peptides and Proteins / metabolism
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Mice
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Mice, Inbred NOD
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Mice, Knockout
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Mice, SCID
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Neoplasm Metastasis
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Neoplasms, Experimental / genetics
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Neoplasms, Experimental / metabolism
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Neoplasms, Experimental / pathology
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / metabolism*
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Proto-Oncogene Proteins c-akt / genetics
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Proto-Oncogene Proteins c-akt / metabolism*
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Reverse Transcriptase Polymerase Chain Reaction
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TOR Serine-Threonine Kinases
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Transplantation, Heterologous
Substances
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FOXO1 protein, human
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Forkhead Box Protein O1
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Forkhead Transcription Factors
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Il2rg protein, mouse
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Interleukin Receptor Common gamma Subunit
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Intracellular Signaling Peptides and Proteins
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MTOR protein, human
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mTOR protein, mouse
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3-Phosphoinositide-Dependent Protein Kinases
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AKT1 protein, human
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AKT2 protein, human
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GSK3B protein, human
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Glycogen Synthase Kinase 3 beta
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Gsk3b protein, mouse
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PDPK1 protein, human
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Pdpk1 protein, mouse
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Protein Serine-Threonine Kinases
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Proto-Oncogene Proteins c-akt
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TOR Serine-Threonine Kinases
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Glycogen Synthase Kinase 3