autologous blood and marrow transplantation - Blog Science ...

Gene Marking to Assess Tumor Contamination
in Stem Cell Grafts for Acute Myeloid Leukemia
Helen E. Heslop, Donna R. Rill, Edwin M. Horwitz,
Charles F. Contant, Robert A. Krance, Malcolm K. Bren
Center for Cell and Gene Therapy (H.E.H., D.R.R., R.A.K., M.K.B.),
and Neurosurgery (C.F.C.), Baylor College of Medicine, Houston, TX,
and Division of Bone Marrow Transplantation (E.M.H.),
St. Jude Children's Research Hospital, Memphis, TN
A B S T R A C T
We have been using gene transfer to investigate the biology of autologous
transplantation in children with acute myeloid leukemia (AML). For the past 7
years, we have used retroviral gene marking of autologous marrow to discover
whether infused marrow contributes to relapse, whether genes may be transferred
into cells that produce long-term repopulation, and how these cells respond to ex
vivo manipulation. In first-generation studies, four of 12 patients relapsed and the
marker gene was definitively detected in three. In second-generation studies
comparing purging techniques, three of 15 patients relapsed and all relapses were
negative for the marker gene. Marker signal has been detected in peripheral blood
granulocytes and T and B cells for up to 6 years at a level of 0.01 to 1%. The
marker gene was also detected in marrow clonogenic assays at a level one log
higher than peripheral blood with no apparent trend for reduction in signal strength
with time. Our results show that retrovirally transduced genes remain detectable for
at least 6 years after transfer to otherwise unmanipulated marrow, and that even
after purging with agents that remove all colony-forming cells, long-term
engraftment still occurs. These data provide an approach by which the long-term
consequences of other stem cell manipulations may be determined in vivo.
INTRODUCTION
Although the role of autologous bone marrow transplantation (autoBMT) in
patients with AML in first remission remains contentious, 1-3
several recent studies
suggest the procedure does reduce the risk of relapse and improve long-term
outcome. 4,5
The major cause of failure after autologous transplant remains relapse.
We initially used gene marking to address the question of whether leukemic cells
in the infused marrow may contribute to relapse. 6
Detection of both the transferred
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