title: Apoptotic cell death induction and angiogenesis inhibition in large established medullary thyroid carcinoma xenografts by Ret inhibitor RPI-1.
abstract: Recent evidence indicates that the success of molecular targeted therapies may depend on the identification of drug targets which are essential for the survival of subsets of tumors. RET oncogenes that have been implicated in the development of thyroid carcinomas are emerging as potential therapeutic targets. In the present study, we investigated the efficacy and the cellular bases of antitumor activity of the indolinone Ret tyrosine kinase inhibitor RPI-1 against large established s.c. TT tumor xenograft, a human medullary thyroid carcinoma (MTC) harboring oncogenic MEN-2A-type RET mutation. Oral treatment with RPI-1 caused growth arrest or regression in 81% treated tumors. Following treatment suspension, tumor inhibition was maintained (51%, P<0.05, 100 days) and cures were achieved in 2/11 mice. In treated tumors, Ret was tyrosine dephosphorylated. Moreover, compared to control tumors, a significant increase in apoptotic cells (210%, P<0.0001), loss of cellularity (47%, P<0.0001) and reduction of microvessel density (36%, P<0.0005) were detected. In vivo effects of RPI-1 were reflected in activation of BAD, cleavage of caspases, apoptotic DNA fragmentation and inhibition of VEGF production observed in in vitro RPI-1-treated TT cells. These findings thus indicate that RPI-1 antitumor effect on the MTC was characterized by apoptosis induction and angiogenesis inhibition. The results, consistent with a dependence on RET oncogene activation for maintenance and survival of MEN2A-type MTC, provide further preclinical rationale for a pharmacological RET-targeted intervention in thyroid cancer.
authors.affiliation: Department of Experimental Oncology and Laboratories, Istituto Nazionale Tumori, Via Venezian 1, 20133 Milan, Italy.
authors.forename: Giovanna
authors.initials: G
authors.lastname: Petrangolini
authors.forename: Giuditta
authors.initials: G
authors.lastname: Cuccuru
authors.forename: Cinzia
authors.initials: C
authors.lastname: Lanzi
authors.forename: Monica
authors.initials: M
authors.lastname: Tortoreto
authors.forename: Sara
authors.initials: S
authors.lastname: Belluco
authors.forename: Graziella
authors.initials: G
authors.lastname: Pratesi
authors.forename: Giuliana
authors.initials: G
authors.lastname: Cassinelli
authors.forename: Franco
authors.initials: F
authors.lastname: Zunino
mesh_terms: D000284:Administration, Oral; D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects*; D018276:Carcinoma, Medullary / Q000188:drug therapy* / Q000473:pathology; D045744:Cell Line, Tumor; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007211:Indoles / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D051379:Mice; D008819:Mice, Nude; D009154:Mutation; D041681:NIH 3T3 Cells; D009389:Neovascularization, Pathologic / Q000517:prevention & control*; D010766:Phosphorylation / Q000187:drug effects; D051096:Proto-Oncogene Proteins c-ret / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D013964:Thyroid Neoplasms / Q000188:drug therapy* / Q000473:pathology; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D007211:Indoles; C477359:RPI-1 compound; D042461:Vascular Endothelial Growth Factor A; D051096:Proto-Oncogene Proteins c-ret