2 . 0 OBJECTIVES 
The objectives of the proposed amendment are to use 
retrovirally-mediated gene transfer into autologous bone 
marrow and peripheral blood cells to study: 
1) Whether retrovirally-mediated gene transfer to human 
hematopoietic long-term reconstituting stem cells is 
feasible using a CD34-enriched / growth factor-stimulated 
target cell population, in preparation for gene therapy 
protocols directed at each of these diseases. 
2) The relative contribution of bone marrow versus 
chemotherapy and growth factor-mobilized peripheral blood 
cells to short-term and long-term reconstitution after 
autologous transplantation. 
3) The kinetics of autologous reconstitution after 
transplantation of CD34-enriched peripheral blood and/or 
bone marrow cells. 
4) The effect of using ablative (multiple myeloma and CML 
protocols) versus less ablative (breast cancer protocol) 
conditioning regimens on the ability to achieve sustained 
engraftment~with transduced progenitor or stem cells. 
5) The effect of different peripheral blood stem cell 
mobilization regimens and pre-bone marrow harvest 
chemotherapy used in the three clinical protocols on gene 
transfer efficiency into progenitor and stem 'cells. 
6) Whether the source of relapse after autologous 
transplantation for metastatic breast cancer, multiple 
myeloma and CML is due to re-infusion of residual clonagenic 
tumor cells persisting in CD34-enriched bone marrow or 
autologous peripheral blood stem cells, or tumor cells 
remaining in the patient even after extensive pre-transplant 
conditioning. 
3.0 SCIENTIFIC RATIONALE AND BACKGROUND 
3 . 1 Rationale : 
The primary rationale for the use of genetic marking in 
these autologous transplantation studies is the inability to 
distinguish whether hematopoietic cells or relapsed tumor 
originates from transplanted autologous cells or from 
residual activity regenerating in the host after 
conditioning. The biology of autologous transplantation is 
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Recombinant DNA Research, Volume 16 
