Gene transfer and the prospects for somatic gene therapy.

Since initial reports of gene transfer into hematopoietic stem cells 4 years ago, progress has been made in both the methodology of gene transfer and the design of vectors. However, substantial problems remain before serious considerations of attempting gene transfer in humans can be made. The efficient transfer of genes into very primitive stem cells capable of long-term repopulation of larger species is a crucial problem. In addition, high level and sustained expression in vivo remains a problem for most transferred sequences. Given the current level of research in the areas of retrovirus vectors and eukaryotic gene regulation, these problems are likely to be resolved in the future.