RET/PTC (rearranged in transformation/papillary thyroid carcinomas) gene rearrangements are the most frequent genetic alterations identified in papillary thyroid carcinoma.     ///    RET/PTC (rearranged in transformation/papillary thyroid carcinomas) tyrosine kinase phosphorylates and activates phosphoinositide-dependent kinase 1 (PDK1): an alternative phosphatidylinositol 3-kinase-independent pathway to activate PDK1..     ///    RET/PTC and PDK1 colocalize in the cytoplasm.     ///    "RET/PTC-induced phosphorylation of the Y9 residue results in increased PDK1 activity, decrease of cellular p53 levels, and repression of p53-dependent transactivation. "    ///    "Moreover, Y9 phosphorylation of PDK1 by RET/PTC does not require phosphatidylinositol 3-kinase or Src activity. "    ///    "In conclusion, RET/PTC-induced tyrosine phosphorylation of PDK1 may be one of the mechanisms by which it acts as an oncogenic tyrosine kinase in thyroid carcinogenesis.. "    ///    "In this report, we show that phosphoinositide-dependent kinase 1 (PDK1), a pivotal serine/threonine kinase in growth factor-signaling pathways, is a target of RET/PTC. "    ///    RET/PTC phosphorylates a specific tyrosine (Y9) residue located in the N-terminal region of PDK1.     ///    Y9 phosphorylation of PDK1 by RET/PTC requires an intact catalytic kinase domain.     ///    "Although the oncogenic potential of RET/PTC is related to intrinsic tyrosine kinase activity, the substrates for this enzyme are yet to be identified. "