While further studies on 62L-LV-mediated transduction of myeloid cells and more importantly CD62L-positive tumor cells will be required, it appears well conceivable that the previously described LVs targeted to the T-cell markers CD8, CD4, or CD3 are more suited for in vivo gene therapy applications than 62L-LV (13, 14, 16, 29, 43, 44). This evidence concerns the gene CD4 and neoplasm.