RESUMO
Gene therapy defines a new therapeutic avenue whose site of action is at the level of the gene itself; viral vectors (adenovirus, retrovirus, herpes virus) or non-viral (liposomes, plasmids) enable the transfer of a fraction of DNA (transgenic) to the target itself. In this review, we present recently acquired data on the mechanisms of oncogenesis and anti-tumor immunity which have enabled the application of several therapeutic strategies in oncology; the transfer of gene(s), coding for cytokines or for coactivation factors in order to develop active immunotherapy; the transfer of suicides genes; the transfer of multidrug resistance gene (MDR1); the transfer of tumor suppressor genes or of cDNA coding for antisense oligonucleotides in order to correct genomic anomalies which are responsible for the malign phenotype. The development of gene therapy demands the resolution of a number of technical difficulties such as vectorisation, targeting, and the expression of the stability of the trans-gene. Phase 1 trials in man have established the innocuity of certain vectors and have confirmed the expression of trans-genes (marker genes). Compared to monogenic hereditary diseases, the "molecular heterogenetic" of bronchial tumours, the consequence of the instability of the genome and the diversity of amplified oncogenes are a major difficulty. In addition, each one of these approaches prevents limiting factors: for example the exclusive targeting of malign cells is an indispensable pre-requisite for the transfer of suicide genes and in the same way the expression the tumour in antigens is the pre-requisite for the development of active immunotherapy. We report the overall results of applied trials for pulmonary carcinomas on murine models and present their applications which are underway in men.