Within the next 2 years, peripheral blood will replace bone marrow
as the medium for autologous transplants, predicted Malcolm A.S.
Moore, DPhil, at a press briefing co-sponsored by the Cancer Research
Institute and Immunex Corporation.
Although numerous issues remain to be resolved for allogeneic
transplants, principally graft-vs-host disease (GVHD), he believes
that within the next decade, the technology for mobilizing peripheral
blood will be sufficiently advanced to render both autologous
and allogeneic bone marrow transplants obsolete.
Once refined, the peripheral blood procedure will be considerably
simpler than bone marrow transplant because it can be done repeatedly,
without general anesthesia, and because a considerably smaller
sample can be expanded for multiple transfusions, said Dr. Moore,
Head of the Laboratory of Developmental Hematopoiesis, Memorial
Sloan-Kettering Cancer Center.
The key, he said, is to stimulate stem cells to appear in the
peripheral blood using colony-stimulating factor treatment. Dr.
Moore, who discovered granulocyte colony-stimulating factor (G-CSF),
cited three such factors currently available: G-CSF, granulocyte-macrophage
CSF(GM-CSF), and stem-cell factor.
None of these, however, accelerate regeneration of platelets.
A newly discovered growth factor, thrombopoietin, does seem to
do so, and more effectively than the interleukins that have thus
far been tried, he said.
Dr. Moore is convinced that many growth factors are needed to
produce the desired effect. He is working with various combinations--what
he terms a "cocktail"--to direct development of specific
cell populations and to expand them, ex vivo, for reinfusion between
In a randomized trial involving patients with metastatic breast
cancer at Memorial Sloan-Kettering, the post-treatment period
of hematopoietic recovery was shortened to 10 to 12 days using
mobilized peripheral blood (compared to 15 to 20 days with bone
marrow transplant). He cautions that the timing of treatment cycles
and infusion of "boosted" blood is crucial, and that
these aspects of treatment still must be fine-tuned.
Umbilical Cord Blood
An even more abundant source of stem cells than peripheral blood
is umbilical cord blood. "It is an intrinsically rich source
of stem cells so, unlike peripheral blood, patients do not need
to be treated with growth factors," Dr. Moore said. With
umbilical cord blood, there is reduced risk of GVHD, and because
the cells are younger, they have greater potential for division,
Cord blood withdrawn and frozen can be used at a future time to
provide needed cells for either autologous or allogeneic transplant.
The New York Blood Center has been awarded an NIH grant to investigate
this application, and has already done 20 allogeneic transplants
using cord blood, he said.