Abstract
To formally test the hypothesis that the
granulocyte/macrophage colony-forming unit (GM-CFU) cells can
contribute to early hematopoietic reconstitution immediately after
transplant, the frequency of genetically modified GM-CFU after
retroviral vector transduction was measured by a quantitative
in
situ
polymerase chain reaction (PCR), which is specific for the
multidrug resistance-1 (MDR-1) vector, and by a quantitative GM-CFU
methylcellulose plating assay. The results of this analysis showed no
difference between the transduction frequency in the products of two
different transduction protocols: “suspension transduction” and
“stromal growth factor transduction.” However, when an analysis
of the frequency of cells positive for the retroviral MDR-1 vector
posttransplantation was carried out, 0 of 10 patients transplanted with
cells transduced by the suspension method were positive for the vector
MDR-1 posttransplant, whereas 5 of 8 patients transplanted with the
cells transduced by the stromal growth factor method were positive for
the MDR-1 vector transcription unit by
in situ
or in
solution PCR assay (a difference that is significant at the
P
= 0.0065 level by the Fisher exact test). These
data suggest that only very small subsets of the GM-CFU fraction of
myeloid cells, if any, contribute to the repopulation of the
hematopoietic tissues that occurs following intensive systemic therapy
and transplantation of autologous hematopoietic cells.
