Abstract
Tumor cells with mutated PTEN proliferate in an EGFR-independent manner. Induction of PTEN sensitizes cells to EGFR inhibition, and the combination causes synergistic apoptosis. Synergy is due to inhibition of two parallel pathways that phosphorylate the proapoptotic protein BAD at distinct sites. Serine 112 phosphorylation is EGFR/MEK/MAPK dependent, whereas serine 136 phosphorylation is PI3K/Akt dependent. Either phosphorylation is sufficient to sequester BAD to 14-3-3. BAD is released and apoptosis is induced only if both serines are dephosphorylated in response to inhibition of both pathways. Reduction of BAD expression by RNA interference prevents apoptosis in response to pathway inhibition. Thus, BAD integrates the antiapoptotic effects of both pathways. Combined inhibition of EGFR and PI3K signaling may be a useful therapeutic strategy.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Carrier Proteins / physiology*
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Cell Line, Tumor
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Cell Survival
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ErbB Receptors / metabolism*
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Humans
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Mice
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Mice, Inbred BALB C
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Neoplasms / enzymology
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Neoplasms / metabolism
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Neoplasms / pathology*
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PTEN Phosphohydrolase
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Phosphatidylinositol 3-Kinases / metabolism*
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Phosphoric Monoester Hydrolases / genetics
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Phosphoric Monoester Hydrolases / physiology*
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Phosphorylation
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Protein Serine-Threonine Kinases / metabolism*
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Proto-Oncogene Proteins / metabolism*
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Proto-Oncogene Proteins c-akt
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RNA Interference
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Signal Transduction / physiology*
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Tumor Suppressor Proteins / genetics
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Tumor Suppressor Proteins / physiology*
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bcl-Associated Death Protein
Substances
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BAD protein, human
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Bad protein, mouse
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Carrier Proteins
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Proto-Oncogene Proteins
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Tumor Suppressor Proteins
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bcl-Associated Death Protein
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ErbB Receptors
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AKT1 protein, human
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Protein Serine-Threonine Kinases
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Proto-Oncogene Proteins c-akt
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Phosphoric Monoester Hydrolases
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PTEN Phosphohydrolase
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PTEN protein, human