Effects of bryostatin-1 on chronic myeloid leukaemia-derived haematopoietic progenitors.
Bryostatin-1 belongs to the family of macrocyclic lactones isolated from the marine bryozoan Bugula neritina and is a potent activator of protein kinase C (PKC). Bryostatin has been demonstrated to possess both in vivo and in vitro anti-leukaemic potential. In samples derived from chronic myeloid leukaemia (CML) patients, it has been demonstrated that bryostatin-1 induces a macrophage differentiation, suppresses colony growth in vitro and promotes cytokine secretion from accessory cells. We investigated the effect of bryostatin-1 treatment on colony-forming unit-granulocyte macrophage (CFU-GM) capacity in the presence of accessory cells, using mononuclear cells, as well as in the absence of accessory cells using purified CD34-positive cells. Cells were obtained from 14 CML patients as well as from nine controls. Moreover, CD34-positive cells derived from CML samples and controls were analysed for stem cell frequency and ability using the long-term culture initiating cell (LTCIC) assay at limiting dilution. Individual colonies derived from both the CFU-GM and LTCIC assays were analysed for the presence of the bcr-abl gene with fluorescence in situ hybridization (FISH) to evaluate inhibition of malignant colony growth. The results show that at the CFU-GM level bryostatin-1 treatment resulted in only a 1.4-fold higher reduction of CML colony growth as compared to the control samples, both in the presence and in the absence of accessory cells. However, at the LTCIC level a sixfold higher reduction of CML growth was observed as compared to the control samples. Analysis of the LTCICs at limiting dilution indicates that this purging effect is caused by a decrease in output per malignant LTCIC combined with an increase in the normal stem cell frequency. It is concluded that bryostatin-1 selectively inhibits CML growth at the LTCIC level and should be explored as a purging modality in CML.
Thijsen
S F
SF
Department of Haematology, Free University Hospital, Amsterdam.
Schuurhuis
G J
GJ
van Oostveen
J W
JW
Theijsmeijer
A P
AP
van der Hem
K G
KG
Odding
J H
JH
Dräger
A M
AM
Ossenkoppele
G J
GJ
D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D054713:Bryostatins; D004789:Enzyme Activation / Q000187:drug effects; D016044:Fusion Proteins, bcr-abl / Q000235:genetics; D006098:Granulocytes / Q000166:cytology / Q000187:drug effects*; D006412:Hematopoietic Stem Cells / Q000187:drug effects*; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007783:Lactones / Q000494:pharmacology*; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000473:pathology*; D018942:Macrolides; D008264:Macrophages / Q000166:cytology / Q000187:drug effects*; D014410:Tumor Stem Cell Assay
D000972:Antineoplastic Agents, Phytogenic; D054713:Bryostatins; D007783:Lactones; D018942:Macrolides; C046785:bryostatin 1; D016044:Fusion Proteins, bcr-abl