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Differential effect of bryostatin 1 and phorbol 12-myristate 13-acetate on HOP-92 cell proliferation is mediated by down-regulation of protein kinase Cdelta.

Abstract
Bryostatin 1 is currently in clinical trials as a cancer chemotherapeutic agent. Although bryostatin 1, like phorbol 12-myristate 13-acetate (PMA), is a potent activator of protein kinase C (PKC), it induces only a subset of those responses induced by PMA and antagonizes others. We report that, in the HOP-92 non-small cell lung cancer line, bryostatin 1 induced a biphasic proliferative response, with maximal proliferation at 1 to 10 nmol/L. This biphasic response mirrored a biphasic suppression of the level of PKCdelta protein, with maximal suppression likewise at 1 to 10 nmol/L bryostatin 1. The typical phorbol ester PMA, in contrast to bryostatin 1, had no effect on the level of PKCdelta and modest suppression of cell proliferation, particularly evident at later treatment times. Flow cytometric analysis revealed changes in the fraction of cells in the G0-G1 and S phases corresponding to the effects on proliferation. Cells overexpressing PKCdelta exhibited a lower rate of cell proliferation compared with control untreated cells and showed neither a proliferative response nor a loss of PKCdelta in response to bryostatin 1. Conversely, treatment with PKCdelta small interfering RNA significantly increased the cellular growth compared with controls. We conclude that the differential effect on cellular proliferation induced by bryostatin 1 compared with PMA reflects the differential suppression of PKCdelta.
AuthorsSung Hee Choi, Tehila Hyman, Peter M Blumberg
JournalCancer research (Cancer Res) Vol. 66 Issue 14 Pg. 7261-9 (Jul 15 2006) ISSN: 0008-5472 [Print] United States
PMID16849575 (Publication Type: Journal Article, Research Support, N.I.H., Intramural)
Chemical References
  • Bryostatins
  • Macrolides
  • bryostatin 1
  • Protein Kinase C-delta
  • Tetradecanoylphorbol Acetate
Topics
  • Bryostatins
  • Carcinoma, Non-Small-Cell Lung (drug therapy, enzymology, genetics, pathology)
  • Cell Growth Processes (drug effects)
  • Cell Line, Tumor
  • Down-Regulation (drug effects)
  • Gene Expression Regulation, Enzymologic (drug effects)
  • Gene Expression Regulation, Neoplastic (drug effects)
  • Humans
  • Lung Neoplasms (drug therapy, enzymology, genetics, pathology)
  • Macrolides (pharmacology)
  • Protein Kinase C-delta (biosynthesis, genetics)
  • Tetradecanoylphorbol Acetate (pharmacology)

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