Current challenges in cancer gene therapy.

The ability to transfer novel genes into mammalian cells has allowed us to conceive of novel strategies towards cancer therapy. Since the initial gene-transfer clinical trial in 1989, over 300 cancer patients have been enrolled in gene therapy trials. Despite this, an NIH-sponsored panel concluded that 'clinical efficacy has not been definitively demonstrated at this time in any gene therapy protocol'. However, the first 8 years of gene therapy research have provided us with insights regarding the areas that require further scientific progress. For example, it is now clear that while in vitro assays of gene-modified haemotopoietic progenitor cells suggest high transduction efficiencies, once these cells are infused in vivo, only a small percentage of circulating transduced cells can be detected. While the initial clinical studies have demonstrated that gene transfer in patients can be safe and feasible, they have also indicated that future research is necessary towards the development of improved gene transfer techniques for these approaches to be successful.