International Journal of Cell Cloning, Vol 4, 3-15, Copyright © 1986 by AlphaMed Press
Synergistic hematopoietic growth factors
PJ Quesenberry
A number of growth factors acting on hematopoietic stem cells have now been
purified and characterized. These include erythropoietin,
granulocyte-macrophage colony-stimulating activity (GM-CSA), granulocyte
colony-stimulating activity and colony-stimulating factor-1 (CSF-1).
Factors which act in concert with these defined factors and appear to act
relatively early in the hematopoietic stem cell lineage are currently under
study. Interleukin 3 appears to have both the characteristics of a
differentiating hormone and the ability to generate proliferation of
relatively early stem cells. Interleukin 3 acts in concert with at least
CSF-1 and erythropoietin to enhance their effect on stem cell proliferation
and differentiation. A new class of hematopoietic growth factor activities
termed synergizing activities also exist. These activities appear to have
no intrinsic capacity to stimulate hematopoietic colony formation by
themselves but enhance the effects of other differentiating hormones such
as GM-CSA and CSF-1. Activities which appear to represent synergizing
activities have now been found to evolve from a human bladder carcinoma
line, a cell line derived from murine marrow adherent cells and normal
murine marrow and thymic cells. These activities may act on very primitive
hematopoietic progenitors to allow them to express receptors to various
differentiating hormones or alternatively they may act as commitment
factors in a commitment-progression model of stem cell regulation.
