therapy will be initiated after marrow recovery in an 
attempt to suppress any residual tumor. Interferon has 
already been shown to prolong responses in myeloma patients 
treated with standard chemotherapy, and a preliminary study 
suggests that interferon administration post-transplantation 
is feasible. 23,24 
Based on prior studies we would predict a 30-50% complete 
response rate to this treatment regimen, and would hope that 
post-transpl.ant interferon could prolong these remissions. 
The estimated treatment-related mortality from this type of 
transplantation regimen is 5-10%, but no less aggressive 
approach has been shown to significantly prolong survival or 
offer the possibility of cure. 
2.4 LABORATORY INVESTIGATIONS: 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. The studies will 
focus on two major issues 1) what are the molecular and cell 
surface antigen characteristics of clonogenic myeloma "stem 
cells" found in the bone marrow and the peripheral blood? 
and 2) which in vitro variables, such as hematopoietic 
growth factors, optimize gene transfer to normal marrow or 
peripheral blood progenitors or to myeloma tumor cells? 
Results could have an impact on possible purging techniques 
now in development, such as positive selection for CD34 
positive early progenitor cells, or negative selection 
against HLA-DR expressing cells, and on future gene therapy 
protocol development. 
2.5 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 stem cells 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 
incubation of target cells with viral supernantant , co- 
culture 1 with autologous or allogeneic marrow stroma, and use 
of hematopoietic growth factors to preserve viability and 
[38] 
Recombinant DNA Research, Volume 16 
