Alterations in tumorigenicity of embryonal carcinoma cells by ICF-I triple-helix induced changes in immunogenicity and apoptosis

IGF-I antisense gene therapy has been applied successfully to animal models of glioma, hepatoma and teratocarcinoma. The antisense strategy has shown that tumor cells transfected with vectors encoding IGF-I antisense RNA lose tumorigenicity, become immunogenic and are associated with tumor specific immune response involving CD8 + lymphocytes. An IGF-I triple helix approach to gene therapy for glioma was recently described. The approach we have ta ken is to establish parameters of change using the IGF-I triple helix strat egy. PCC-3 embryonal carcinoma cells derived from murine teratocarcinoma wh ich express IGF-I were used as a model. The cells were transfected with vec tor which encodes an oligoribonucleotide that forms RNA - IGF-I DNA triple- helix structure. The triple helix stops the production of IGF-I. Cells tran sfected in this manner underwent changes in phenotype and an increase in MH C-I and B-7 cell surface molecules. They also showed enhancement in the pro duction of apoptotic cells (60-70%). The << triple helix >> transfected cel ls lost the ability to induce tumor when injected subcutaneously in syngene ic 129 Sv mice. When co-transfected in vitro with expression vectors encodi ng both MHC-I and B-7 cDNA in antisense orientation, the << triple-helix >> transfected cells were down-regulated in expression of MHC-I and B-7 and t he number of apoptotic cells was significantly decreased, Injection of the doubly co-transfected cells into 129 Sv mice was associated with induction of teratocarcinoma. Comparison between antisense and triple-helix transfect ed cells strategies showed similar immunogenic and apoptotic changes. The f indings suggest that triple-helix technology may offer a new clinical appro ach to treatment of tumors expressing IGF-I. (C) 2000 Elsevier Science Inc. All rights reserved.