Recombinant DNA Advisory Committee - 06/1-2/92 
In response to Dr. Doi's question regarding the variation in transduction rates between 
patients, Dr. Deisseroth noted that Dr. Brenner has observed the same variation in 
transduction in patients with AML. One eligibility requirement for entering this protocol 
is that patients will be screened to ensure that their cells will be transduced at a 
measurable frequency. 
Dr. Deisseroth explained that there is no sensitive method available for detecting 
leukemic progenitors in the patient's peripheral blood after delivery of the preparative 
regimen prior to transplant. The investigators have to wait until hematopoietic function 
is restored to observe the presence or absence of leukemic cells. 
In response to questions regarding the selection for CD34(+) cells, Dr. Deisseroth stated 
that it is common for early progenitor cells and normal diploid cells to proliferate 
following conventional dose chemotherapy or interferon treatments. One hypothesis is 
that CML is a disease in which the Philadelphia positive chromosome selectivity 
promotes the expansion of late progenitors, having little impact on early progenitor 
phenotype. Fractionation to enrich CD34( + ) cells results in a decline in Philadelphia 
chromosome positive cells. The population of diploid cells obtained from patients 
following conventional dose chemotherapy will be enriched in normal cells by CD34( + ) 
selection. 
Dr. Deisseroth stated that CD34( + )/HLA-DR(-) selection has been performed in nine 
CML patients. Selections were performed on bone marrow as well as peripheral blood 
cells. Large numbers of cells were selected that generate rapid diploid reconstitution in 
these CML patients. 
In response to Dr. Doi's questions regarding possible mechanisms or assays that will aid 
in monitoring hematopoietic reconstitution and evaluation of the patient's peripheral 
blood and bone marrow, Dr. Deisseroth said that he is currently perfecting a fluorescent 
in situ hybridization technique for the detection of Philadelphia chromosome positive 
cells. Once perfected, results will not have to be based solely on PCR data, but can be 
obtained by microscopic observation of these cells. Dr. Deisseroth presented 
photographs that detailed the sensitivity of this in situ hybridization technique. 
Dr. Deisseroth responded to Dr. Brinckerhoffs question about the frequency of marking 
with LNL6 versus GINa. Data was presented using bone marrow cells obtained from 
CML patients. The cells of 7 patients were transduced with LNL6 versus 16 patients 
with GINa. The imbalance of data was attributable to the fact that there was not as 
much of the LNL6 vector available from GTI at the time the experiments were 
performed. Dr. Deisseroth noted that preliminary data is available demonstrating that 
double marking occurred, and he is confident that CML cells will be transduced by both 
vectors with equal frequencies. 
Recombinant DNA Research, Volume 15 
[701] 
