intensive therapy. Since the two safety modified retroviruses 
are used for separately marking the peripheral blood and 
marrow stem cells which differ only in a PCR detectable 
difference in sequences in the virus, the relative 
contribution of the marrow and peripheral blood to 
hematopoietic reconstitution and to relapse can be measured. 
The patients will then be followed at three weekly intervals 
during and after hematopoietic reconstitution and at six 
monthly intervals thereafter with PCR's for bcr-abl and the 
two neo positive safety modified retroviral sequences in the 
peripheral blood or marrow. This analyses will clarify the 
relative contribution of the peripheral blood and marrow to 
hematopoietic recovery. This will also be done at the time of 
relapse with colony growth, PCR, FISH, and cytogenetic assays 
of the colonies to determine if the blast cells that arise 
after relapse are marked with a retroviral vector and, 
therefore, arising from the infused autologous cells or 
whether they arise from residual systemic disease (in this 
case, no marker will be detectable) . There are four potential 
results of this experiment: (1) A rare patient will have 
virus positive autologous leukemia blast cells, but these will 
be clonal (i.e., the vector integrating site will be clonal). 
The same normal cells may have a polyclonal vector integration 
site. This will indicate that the infused autologous cells 
are the origin of relapse but that relapse arises from a 
single cell; (2) Leukemia blast cells are positive for vector 
and the vector integration site is polyclonal. Normal cells 
may also have polyclonal integration sites. This will 
indicate that multiple leukemia blast cells contained within 
the infused autologous stem cells give rise to the relapse; 
(3) Both normal and leukemia blast cells are marked with a 
clonal vector integration site. This will indicate that the 
disease arises from a pluripotent stem cell which is 
undergoing leukemic conversion spontaneously; and (4) No 
marker is seen suggesting relapse arises from systemic 
disease. In cases 1 and 2, further development of purging 
procedures for the autologous cells needed for transplant 
would be indicated. Retroviral marking will permit us to 
select either the purification of normal progenitor cells or 
systemic-preparative regimens as areas in which modifications 
must be made in order to achieve increased number of stable 
cytogenetic remissions. 
3.0 BACKGROUND DRUG INFORMATION (See Appendices C and D for 
chemotherapy (cyclophosphamide and VP-16, respectively), 
Appendix E for interferon, and Appendix G for the LNL-6 and 
GINa viruses) . 
4.0 PATIENT ELIGIBILITY 
4.1 Interferon refractory CML patients in second chronic 
phase, accelerated phase or blast crisis, who are 
ineligible for allografting, less than 60 years of age 
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Recombinant DNA Research, Volume 15 
