marrow harvesting after 5-FU. Since Group 2 patients are at 
high risk for early relapse or progression, patients will 
proceed immediately to treatment with high dose 
cyclophosphamide/TBI and autologous PBSC/marrow 
transplantation coupled with G-CSF. 
After hematologic recovery from transplant, all 
patients in both groups will receive interferon since 
responses to interferon post-transplant have been observed 
even in patients who demonstrate interferon-resistance pre- 
transplant. 2 
We plan to carry out a Phase II study of 24 patients 
accomplished jointly at the NIH and the University of 
Virginia. The therapeutic endpoints of this study will 
include an assessment of toxicity, response (clinical, 
hematologic, and cytogenetic) , relapse-free survival and 
overall survival. 
We plan to carry out a number of studies utilizing 
molecular, in vitro culture and cell sorting techniques on 
small aliquots of patient bone marrow and peripheral blood 
stem cell harvests obtained pre-transplant, and on 
diagnostic samples obtained post-transplant and at the time 
of relapse. Patient marrow and blood samples will undergo 
purification for stem cell/progenitor cell populations using 
CD34+ column separation. Cell populations will be evaluated 
for infectivity with retroviral vectors and the effect of 
growth factors such as stem cell factor, IL-3 and IL-6 on 
potentiation of leukemic cell growth; transduced cells will 
be evaluated for long term bone marrow repopulating ability 
in long term culture with cell supernatants evaluated for 
progenitor cell content and neomycin resistance, polymerase 
chain reaction (PCR) to detect NEO gene or reverse 
transcriptase PCR to detect bcr-abl mRNA in individual 
colonies . 
Future plans: 
After analysis of the in vitro studies outlined above, 
we plan to incorporate a gene marking procedure into this 
protocol. Specifics of the gene marking protocol will be 
submitted to the IRB and to the Recombinant DNA Advisory 
Committee as a protocol amendment at a later date. We would 
plan to enrich a portion of both the harvested bone marrow 
and peripheral blood for early progenitor and stem cells via 
CD34 positive selection, and expose the cells to supernatant 
containing a replication incompetent retroviral vector which 
carries the bland marker gene for neomycin resistance. 
Exposure to viral supernatant will be carried out under 
conditions previously shown by many laboratories, including 
our own, to be necessary for efficient retroviral 
transduction, including a prolonged co-culture with 
autologous or allogeneic marrow stroma, and use of 
hematopoietic growth factors to preserve viability and 
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Recombinant DNA Research, Volume 16 
