Regulation of nuclear Beta-catenin in EGFR-promoted tumor development.

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DESCRIPTION (provided by applicant): Overexpression of epidermal growth factor (EGF) receptor (EGFR) and transactivation of ß-catenin have been detected separately in many human tumors and correlate with a poor clinical prognosis. We recently revealed that EGFR activation induces ß-catenin transactivation in a glycogen synthase kinase-3ß (GSK3ß)-canonical pathway-independent manner. However, how EGFR-induced signaling regulates nuclear ß-catenin transactivation and thereby promotes tumor progression remains unclear. Pyruvate kinase isozyme type M2 (PKM2), which regulates the rate-limiting final step of glycolysis, is instrumental for tumorgenesis. In addition to its well-studied role in cell metabolism, PKM2 promotes cell proliferation though an unknown mechanism. Our preliminary data showed that activation of EGFR results in PKM2 nuclear translocation. In addition, nuclear translocated PKM2 interacts with ß-catenin and mediates ß-catenin-regulated gene transcription. We hypothesize that regulation of ß-catenin by interacting with nuclear PKM2 plays an instrumental role in EGFR-promoted tumor development. In Specific Aim 1, we will determine the mechanisms underlying EGF-induced PKM2 nuclear translocation. In Specific Aim 2, we will determine whether the interaction between nuclear PKM2 to ß-catenin is essential for EGF-induced ß-catenin transactivation. In Specific Aim 3, we will differentiate the functions of cytosolic and nuclear PKM2 and determine the role of ß-catenin regulation by PKM2 in EGFR-promoted tumor development. We expect that our proposed research will provide important and previously unrevealed mechanisms of EGFR-promoted tumor development via crosstalking EGFR with Wnt pathways, which are dependent on nonmetabolic functions of PKM2. Building on our findings, therapy strategies targeting EGF-induced ß-catenin regulation may be developed to enhance current EGFR-based cancer therapies.