The action of bryostatin on normal human hematopoietic progenitors is mediated by accessory cell release of growth factors.
Since enrichment of human bone-marrow hematopoietic progenitors is becoming more feasible and since purified growth factors are now available, we sought to study the action of growth factors on CD34-positive enriched cultures of human bone-marrow cells. We tested the effect of recombinant human (rh) granulocyte-macrophage colony-stimulating factor (GM-CSF), rh interleukin-3 (IL-3), or a unique biologic response modifier, bryostatin 1, on the growth of purified CD34 cells obtained by limiting dilution in single-cell cultures. We have shown previously that bryostatin 1 stimulates both myeloid and erythroid progenitors of human origin in vitro. In this study both IL-3 and GM-CSF supported colony formation from 500, 100, or single-cell cultures at equivalent plating efficiences, suggesting a direct action of these factors on hematopoietic cell growth. Conversely, bryostatin 1 did not support the growth of CD34 cells in single-cell cultures, and the cloning efficiency increased with increasing the number of cells in the culture. To test whether the indirect action of bryostatin 1 might be mediated through the production of growth factors by accessory cells, studies were performed using antibodies directed against human IL-3 and GM-CSF in culture with bryostatin 1 and normal human bone-marrow cells. Results are consistent with the hypothesis that bryostatin 1 could have a stimulatory effect on the accessory cell populations to produce either IL-3 or GM-CSF. Further support for this notion was obtained by demonstrating that T cells, which are cells known to be able to produce IL-3 and GM-CSF, are stimulated by bryostatin 1 to express messenger RNA (mRNA) for specific growth factors, including GM-CSF. These results provide further support that bryostatin 1 may be a useful clinical agent to stimulate hematopoiesis in vivo.
Johns Hopkins Oncology Center, Baltimore, MD 21205.
S J
SJ
Sharkis
R J
RJ
Jones
M L
ML
Bellis
G D
GD
Demetri
J D
JD
Griffin
C
C
Civin
W S
WS
May
D000906:Antibodies / Q000276:immunology; D000938:Antigen-Presenting Cells / Q000378:metabolism* / Q000502:physiology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D015152:Blotting, Northern; D054713:Bryostatins; D002455:Cell Division / Q000187:drug effects; D003115:Colony-Stimulating Factors / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D006133:Growth Substances / Q000235:genetics / Q000276:immunology / Q000378:metabolism* / Q000494:pharmacology; D006410:Hematopoiesis / Q000187:drug effects; D016298:Hematopoietic Cell Growth Factors; D006412:Hematopoietic Stem Cells / Q000187:drug effects*; D006801:Humans; D007377:Interleukin-3 / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology; D007783:Lactones / Q000494:pharmacology*; D018942:Macrolides; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
D000906:Antibodies; D000970:Antineoplastic Agents; D054713:Bryostatins; D003115:Colony-Stimulating Factors; D006133:Growth Substances; D016298:Hematopoietic Cell Growth Factors; D007377:Interleukin-3; D007783:Lactones; D018942:Macrolides; D012333:RNA, Messenger; C046785:bryostatin 1; D016178:Granulocyte-Macrophage Colony-Stimulating Factor