First generation adenoviral vectors, the vector par excellence for immuno-gene therapy of cancer

Gene therapy is a new promising therapeutic alternative for a number of diseases in which traditional treatments are unsuccessful. Basically, gene therapy consists in the introduction of genetic material into target cells with the purpose to produce a therapeutic benefit. Recent advances in this area of biomedicine have lead to the development of an ever-increasing list of gene therapy clinical trials for the treatment of different diseases, such us malignant, infectious, autoimmune, and genetic diseases. In most of the gene therapy approaches the use of a vehicle, called vector, to deliver the genetic material into the cells is required. Vectors can derive from genetically modified virus or can be of nonviral origin. In spite of a variety of vector systems developed, a universal vector adaptable to the diverse experimental or clinical conditions is not available. Due to their properties such as high transduction efficiency, wide cellular/ tissular tropism, easy handling and production, Adenoviral vectors have been extensively used in cancer therapy and an important amount of experience has been accumulated during the last decade. In spite of their high immunogenicity that limits transgene expression to a short period of time, first generation adenoviral vectors have demonstrated their efficacy in several immunotherapy strategies against experimental tumour models as well as in phase I clinical trials. This article reviews currently available viral vectors for gene therapy, biological properties of adenoviruses, the different versions of adenoviral vectors and methods to construct first generation adenoviral vectors with special emphasis in cancer immunotherapy approaches.