RETMEN2A and RETMEN2B Oncoproteins are Targets of PP1 Inhibitor

RET/PTC Oncoproteins: Molecular Targets of New Drugs

Ret oncoproteins expressed in thyroid carcinomas represent possible targets for therapeutic intervention. Oncogenic activation of the receptor tyrosine kinase encoding RET gene occurs typically by gene rearrangement in papillary thyroid carcinomas (PTC) and by missense mutation in medullary thyroid carcinomas (MTC). These genetic alterations lead to the expression of deregulated products characterized by ligand-independent activation of the intrinsic tyrosine kinase of Ret. Such features suggest the possibility of using specific tyrosine kinase inhibitors to block the Ret oncoproteins signaling. The present report summarizes the cellular effects of the arylidene 2-indolinone Ret inhibitor RPI-1 (formerly Cpd1) on the human PTC cell line TPC-1 which spontaneously harbors the RET/PTC1 oncogene. The results provide evidence that RPI-1 is able to inhibit cell growth and to interfere with Ret/ptc1-driven signaling. These findings support a role for Ret oncoproteins as therapeutic targets and the pharmacological interest of RPI-1 as a candidate drug for preclinical evaluation on thyroid tumors expressing RET oncogenes.

Multiple endocrine neoplasia type 2B and Hirschsprung's disease

Multiple endocrine neoplasia type 2B and Hirschsprung's disease are genetic disorders characterized by gross and/or microscopic pathology of the enteric nervous system and associated dysmotility. A specific missense mutation in the RET proto-oncogene is the etiology of multiple endocrine neoplasia type B, in contrast to very complex multigenetic defects that underlie Hirschsprung's disease, which include overt mutations and more subtle changes in the RET locus. In this review, the molecular genetics of the 2 conditions are discussed, and the clinical implications of existing data and future studies are summarized.