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Miranda C.,Operative Unit Molecular Mechanisms | Fumagalli T.,Operative Unit Molecular Mechanisms | Anania M.C.,Operative Unit Molecular Mechanisms | Vizioli M.G.,Operative Unit Molecular Mechanisms | And 3 more authors.
PLoS ONE | Year: 2010

TRK oncoproteins are chimeric versions of the NTRK1/NGF receptor and display constitutive tyrosine kinase activity leading to transformation of NIH3T3 cells and neuronal differentiation of PC12 cells. Signal Transducer and Activator of Transcription (STAT) 3 is activated in response to cytokines and growth factors and it has been recently identified as a novel signal transducer for TrkA, mediating the functions of NGF in nervous system. In this paper we have investigated STAT3 involvement in signalling induced by TRK oncogenes. We showed that TRK oncogenes trigger STAT3 phosphorylation both on Y705 and S727 residues and STAT3 transcriptional activity. MAPK pathway was involved in the induction of STAT3 phosphorylation. Interestingly, we have shown reduced STAT3 protein level in NIH3T3 transformed foci expressing TRK oncogenes. Overall, we have unveiled a dual role for STAT3 in TRK oncogenes-induced NIH3T3 transformation: i) decreased STAT3 protein levels, driven by TRK oncoproteins activity, are associated to morphological transformation; ii) residual STAT3 transcriptional activity is required for cell growth. © 2010 Miranda et al. Source

Borrello M.G.,Operative Unit Molecular Mechanisms | Aiello A.,Foundation Medicine | Peissel B.,Foundation Medicine | Rizzetti M.G.,Operative Unit Molecular Mechanisms | And 9 more authors.
Endocrine-Related Cancer | Year: 2011

Activating mutations of RET, a gene encoding two isoforms of a tyrosine kinase receptor physiologically expressed in several neural crest-derived cell lineages, are associated with the inherited forms of medullary thyroid carcinoma (MTC). The identification and characterization of novel RET mutations involved in MTC is valuable, as RET gene testing plays a crucial role in the management of these patients. In an MTC patient, we have identified a germline c.1996A>G transition in heterozygosis leading to K666E substitution. In addition, the conservative S904S (c.2712C>G) and the non-conservative functional G691S (c.2071G>A) polymorphisms have been identified. Through functional studies, we demonstrate for the first time that K666E is a gain-of-function mutation with oncogenic potential, based on its ability to transform NIH3T3 cells. It was not possible to define whether K666E is a de novo or inherited RET variant in the patient, as the family history was negative for MTC, and the carrier status of family members could not be tested. Our results, together with a recent report of co-segregation of the mutation in three MTC families, suggest that K666E is a causative MTC mutation. As we have shown that the same patient allele carries both K666E and G691S variants, the latter known to increase downstream RET signaling, a possible role for the G691S polymorphism has also been investigated. We have demonstrated that, although RET-G691S is not oncogenic per se, it enhances the transforming activity of the RET-K666E mutant, thus suggesting a modifier role for this functional polymorphism. © 2011 Society for Endocrinology. Source

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