Bryostatin 1 activates protein kinase C and induces monocytic differentiation of HL-60 cells.
Phorbol esters induce the human HL-60 promyelocytic cell line to differentiate along a monocytic pathway. This induction of differentiation may involve phorbol ester-induced activation of the phospholipid- and calcium-dependent protein kinase C. Bryostatin 1, a macrocyclic lactone, has been shown to compete with phorbol esters for binding to protein kinase C. We have confirmed that bryostatin 1 translocates activity of protein kinase C from the cytosolic to membrane fractions of HL-60 cells. The present results also demonstrate that bryostatin 1 (10 nmol/L) induces monocytic differentiation of HL-60 cells as determined by adherence, growth inhibition, appearance of monocyte cell surface antigens, and alpha-naphthyl acetate esterase staining. Furthermore, bryostatin 1 (10 nmol/L) downregulated c-myc expression and induced c-fos, c-fms, and tumor necrosis factor transcripts. These changes in gene expression induced by bryostatin 1 are similar to those associated with phorbol ester-induced monocytic differentiation of HL-60 cells. In contrast, exposure to a higher concentration of bryostatin 1 (100 nmol/L) had less of an effect on growth inhibition of HL-60 cells and changes in gene expression. Moreover, 100 nmol/L bryostatin 1 antagonized the cytostatic effects and adherence induced by phorbol esters. Our results thus suggest that bryostatin 1 activates HL-60 cell protein kinase C and that this effect is associated with induction of monocytic differentiation.
Stone
R M
RM
Laboratory of Clinical Pharmacology, Dana-Farber Cancer Institute, Boston, MA 02115.
Sariban
E
E
Pettit
G R
GR
Kufe
D W
DW
D054713:Bryostatins; D002454:Cell Differentiation / Q000187:drug effects*; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D007783:Lactones / Q000494:pharmacology*; D018942:Macrolides; D008934:Mitogens / Q000494:pharmacology*; D009000:Monocytes / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D011519:Proto-Oncogenes / Q000187:drug effects; D012313:RNA / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects
D054713:Bryostatins; D007783:Lactones; D018942:Macrolides; D008934:Mitogens; C046785:bryostatin 1; D012313:RNA; D011493:Protein Kinase C