Effect of the protein kinase C activating agent bryostatin 1 on the clonogenic response of leukemic blast progenitors to recombinant granulocyte-macrophage colony-stimulating factor

Steven Grant, George Pettit, Craig Howe, Carl McCrady

Research output: Contribution to journalArticlepeer-review

22 Scopus citations

Abstract

Bryostatin 1 is a macrocyclic lactone activator of protein kinase C which has displayed promising antileukemic potential in pre-clinical studies. We have assessed the effect of bryostatin 1 on the in vitro clonogenic response of leukemic myeloblasts obtained from 12 patients with acute non-lymphocytic leukemia to recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF), and have compared these responses to those of normal human hematopoietic progenitors. Although leukemic blast progenitors responded in a heterogenous manner to bryostatin 1 as a single agent, co-administration of 12.5 or 100nM bryostatin 1 in conjunction with 1.25 ng/ml rGM-CSF resulted in a significant reduction in colony formation (compared to rGM-CSF alone) in 8/ 12 specimens, and sub-additive stimulatory effects in all samples. In addition, the exposure of cells to 12.5 nw bryostatin 1, either alone or in conjunction with 1.25 ng/ml rGM-CSF, substantially reduced or eliminated leukemic cell self-renewal capacity in all samples assayed. In contrast to the effects observed in leukemic cells, exposure of adherent and T-cell depleted normal bone marrow mononuclear cells to equivalent concentrations of bryostatin 1 and rGM-CSF consistently produced supra-additive effects on the growth of normal committed myeloid progenitors (day 14 CFU-GM). When normal marrow cells were further enriched for progenitors (MY-10*), concentrations of bryostatin 1 that were unable to support growth when administered alone significantly potentiated the number of GM colonies formed in response to rGM-CSF. These studies suggest that bryostatin 1 may modulate the in vitro response of certain normal and leukemic progenitor cells to rGM-CSF, and that the nature of this response differs between the two cell types. They also indicate that bryostatin 1 may be particularly effective in limiting the self-renewal capacity of leukemic myeloblasts, an in vitro characteristic with potentially important in vivo significance.

Original languageEnglish (US)
Pages (from-to)392-398
Number of pages7
JournalLeukemia
Volume5
Issue number5
StatePublished - May 1991

ASJC Scopus subject areas

  • Hematology
  • Oncology
  • Cancer Research

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