title: Antitumor capacity of a dominant-negative RET proto-oncogene mutant in a medullary thyroid carcinoma model.
abstract: Gain-of-function mutations in the RET proto-oncogene resulting in a constitutively active receptor tyrosine kinase have been identified as responsible for three subtypes of multiple endocrine neoplasia type 2 (MEN-2) and the development of sporadic medullary and papillary thyroid carcinoma. An important strategy in cancer gene therapy is the inhibition of oncogenic signal transduction by interfering with the molecular mechanisms of activation. In the present study, we tested the therapeutic capacity of an adenovirus expressing a dominant-negative (dn) RET mutant, RET(51).flag, under the control of a synthetic C cell-selective calcitonin promoter (TSE2.CP1) against human medullary thyroid cancer (MTC). Infection of human MTC-derived TT cells with Ad-TSE2.CP1-dn-RET(51).flag resulted in the accumulation of immature RET protein in the endoplasmic reticulum and a strong reduction of oncogenic RET receptor on the cell surface, indicating that RET(51).flag exhibits a dominant-negative effect over endogenous oncogenic protein. Analysis of potential downstream mechanisms associated with the inhibition of oncogenic RET signaling by overexpression of mutant RET(51).flag revealed a significant loss of cell viability in TT cells due to the induction of apoptosis. Finally, we examined the antitumor activity of the dominant-negative RET approach in vivo. Inoculation of Ad-TSE2.CP1- dn-RET(51).flag-expressing MTC cells into nude mice led to complete suppression of tumor growth. Moreover, a single intratumoral injection of Ad-TSE2.CP1-dn-RET(51).flag into established thyroid tumors resulted in prolonged survival of treated mice compared with the controls. Our data suggest that adenoviral delivery of dn-RET(51).flag may be a reliable strategy of effective molecular intervention for RET oncogene-related MTC.
authors.affiliation: Center for Cancer Research and Cancer Therapy, Institute of Molecular Biology, University of Essen Medical School, 45122 Essen, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Drosten
authors.forename: T
authors.initials: T
authors.lastname: Stiewe
authors.forename: B M
authors.initials: BM
authors.lastname: Pützer
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D017209:Apoptosis; D018276:Carcinoma, Medullary / Q000378:metabolism / Q000473:pathology / Q000628:therapy*; D002455:Cell Division; D002461:Cell Line, Transformed; D005455:Fluorescent Antibody Technique; D015316:Genetic Therapy; D005822:Genetic Vectors; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D009154:Mutation; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000032:analysis / Q000235:genetics* / Q000276:immunology; D051096:Proto-Oncogene Proteins c-ret; D020794:Receptor Protein-Tyrosine Kinases / Q000032:analysis / Q000235:genetics* / Q000276:immunology; D013964:Thyroid Neoplasms / Q000378:metabolism / Q000473:pathology / Q000628:therapy*; D014407:Tumor Cells, Cultured
chemical_list: C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D051096:Proto-Oncogene Proteins c-ret; D020794:Receptor Protein-Tyrosine Kinases; C494999:Ret protein, mouse