This study aims to transfer a gene that becomes the normal hosttissue less sensitive to cytotoxic drug. But we must the leukemiacells from gain a MDR gene. Trying to transfer MDR to normalhemopoietic cells to save it from the effect of cytotoxic drugs. Themost famous one is MDR-1 transfer, DHFR gene transfer. It is not a direct therapy but it is so important like a therapy. Itused to gained information for improving the outcome of therapyand is the patient need more therapy or not, we can know also thesource of the relapse. By marking the BM at the time of harvestingby a vector and mark the gene present in the malignant cells. Thismarker may be neomycin resistant gene we can follow it inprogenitor cells and peripheral blood. Can use also 2 markers ifusing two vectors, one marker for each vector, so we can comparebetween them, which of them is more effective