Abstract
As a consequence of the dramatic progress that has been made in recent years towards elucidating the diverse molecular events involved in the development and pathogenesis of malignant disease, there is now no shortage of genes that can be exploited or targeted in the context of cancer gene therapy. Many of these have been shown to be effective both in vitro and in various animal models, and a number have progressed to the clinic. The results of these later studies, although generally encouraging, are perhaps less dramatic than one might have hoped. Although a number of factors undoubtedly contribute to this finding, it is evident that a major reason relates to the difficulties implicit in achieving efficient in vivo gene transfer, particularly in a clinical context. Targeting gene therapy, not to the malignant population, but instead to the vasculature upon which the survival and growth of a tumour depends constitutes an alternative approach that overcomes some of the delivery problems associated with established tumour cell-directed strategies.