RETROVIRAL GENE TRANSDUCTION OF ADULT PERIPHERAL-BLOOD OR MARROW-DERIVED CD34(-FACTORS OR ON AUTOLOGOUS STROMA DOES NOT IMPROVE MARKING EFFICIENCY ASSESSED IN-VIVO() CELLS FOR 6 HOURS WITHOUT GROWTH)

Our previous work in patients undergoing autologous transplant for mul tiple myeloma (MM) or breast cancer (BC) has shown that retroviral tra nsduction of adult CD34(+) cells for 72 hours in the presence of inter leukin-3 (IL-3), IL-6, and stem cell factor (SCF) resulted in .01% to 1% long-term marking of peripheral blood and marrow cells (Blood 85:39 48, 1995). In this study we compare these previous studies to transduc tion with no added growth factors, previously shown to result in highe r levels of marking in children (Lancet 342:1134, 1993) or transductio n in the presence of an autologous stromal layer. Peripheral blood (PB ) mononuclear cells were collected via apheresis after high-dose cyclo phosphamide and granulocyte colony-stimulating factor. Bone marrow (BM ) was also harvested in all patients. One third of both BM and PB coll ections were enriched for CD34(+) cells and transduced with one of two marking vectors containing the neomycin-resistance gene to distinguis h cells originating from BM and PB posttransplantation. Cells from 3 M M and 2 BC patients were transduced without growth factors for 6 hours and cells from 2 MM and 2 BC patients were transduced in the presence of autologous marrow stroma. Immediately posttransduction, the percen tage of Neo-resistant PB and BM progenitors (colony-forming units) wer e: 0% to 19% in the g-hour no growth factor group and 0% to 36% in the autologous stroma group. After conditioning therapy, both transduced and untransduced PB and BM fractions were infused into the patients. S emi-quantitative nested DNA polymerase chain reaction was performed on total, mononuclear, and granulocyte fractions of PB and BM at 1, 3, 6 , 9, 12, and 18 months. Poor marking has been observed in both groups, with no consistently positive patients. These results compare unfavor ably with our prior experience using growth factors during transductio n. Further optimization of transduction conditions and vectors needs t o be developed to improve transduction efficiency of adult human repop ulating hematopoietic cells.