A new therapeutic approach in medullary thyroid cancer treatment: inhibition of oncogenic RET signaling by adenoviral vector-mediated expression of a dominant-negative RET mutant.
BACKGROUND
Mutations in the RET proto-oncogene that result in constitutive tyrosine kinase activity are the underlying cause for the development of medullary thyroid cancer (MTC). To investigate an alternative strategy in MTC treatment, we took advantage of a dominant-negative RET (dn-RET) mutant, Ret(51)HSCR32, which inhibits oncogenic signal transduction by retaining the oncogenic RET protein in the endoplasmic reticulum, thereby reducing the amount of oncogenic RET protein from the cell surface. METHODS; We constructed an adenoviral (Ad) vector expressing dn-RET under control of the C-cell specific synthetic calcitonin promoter TSE2.CP1 (AdTSE2.CP1-RET(51)HSCR32) and investigated the effect of dn-RET on cell growth of MTC-derived TT cells.


RESULTS
Analysis of the subcellular localization of endogenous oncogenic RET protein showed a significant dominant-negative effect of Ad vector-delivered dn-RET in TT cells, resulting in a strong inhibition of cell viability. The observed effect is partially dependent on growth inhibition and possibly apoptosis induction.


CONCLUSIONS
In the present study, growth of human MTC cells was successfully inhibited by Ad vector-mediated delivery of RET(51)HSCR32, suggesting that inhibition of oncogenic RET receptor tyrosine kinase expression by a dn-RET mutant might be a powerful approach for in vivo therapy of MTC.
Drosten
Matthias
M
Center for Cancer Research and Cancer Therapy, Institute of Molecular Biology, University of Essen Medical School, Hufelandstrasse 55, 45122 Essen, Germany.
Frilling
Andreja
A
Stiewe
Thorsten
T
Pützer
Brigitte M
BM
D000256:Adenoviridae / Q000235:genetics; D018276:Carcinoma, Medullary; D002470:Cell Survival; D029721:Drosophila Proteins; D015972:Gene Expression Regulation, Neoplastic; D005799:Genes, Dominant; D015316:Genetic Therapy; D005822:Genetic Vectors; D006801:Humans; D066298:In Vitro Techniques; D011401:Promoter Regions, Genetic / Q000235:genetics; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D051096:Proto-Oncogene Proteins c-ret; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics*; D015398:Signal Transduction / Q000235:genetics; D013964:Thyroid Neoplasms; D014407:Tumor Cells, Cultured / Q000166:cytology / Q000502:physiology
D029721:Drosophila Proteins; C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D051096:Proto-Oncogene Proteins c-ret; D020794:Receptor Protein-Tyrosine Kinases; C416649:Ret protein, Drosophila