Cytostatic and cytotoxic properties of the marine product bistratene A and analysis of the role of protein kinase C in its mode of action

Biochem Pharmacol. 1993 May 5;45(9):1753-61. doi: 10.1016/0006-2952(93)90430-5.

Abstract

Bistratene A is a polyether which was isolated from the marine ascidian Lissoclinum bistratum Sluiter. The hypothesis has been tested that the cytostatic effect of bistratene A is mediated by modulation of protein kinase C (PKC). Human-derived A549 lung and MCF-7 breast adenocarcinoma cells are extremely sensitive to growth inhibition induced by activators of PKC. Therefore, the effect of bistratene A on these cell lines was compared with that of the known PKC activator 12-O-tetradecanoylphorbol-13-acetate (TPA). The ability of bistratene A to modulate PKC activity in cellular cytosol was assessed to determine the involvement of PKC in the induction of cytostasis. Bistratene A inhibited the growth of both cell lines and initial seeding density determined its cytostatic potency. IC50 values were between 1.0 and 2.9 nM. Bistratene A also had a profound effect on the colony forming ability of A549 cells, preventing clonal growth at 5 nM. Using the incorporation of [3H]thymidine into cells to assess DNA synthetic activity and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay to define cytotoxicity, the compound was found to have both cytostatic and cytotoxic properties. Bistratene A decomposed by 50% after only 2.8 hr in cell culture medium. TPA induced rapid motility and the formation of a network of branched colonies in both cell lines grown on Matrigel, whereas bistratene A did not cause the same effect. Cell cytosol was analysed for phorbol ester binding sites after treatment with bistratene A or TPA. Incubation with TPA (10 nM) caused a reduction in binding sites to 57% of binding in control cells after 30 min and to 35% after 24 hr. Bistratene A did not cause a significant change in binding sites. Assays of PKC activity in cellular cytosol revealed that bistratene A was unable to activate or inhibit the enzyme at concentrations of up to 10 microM. The results suggest that bistratene A is an exquisitely potent cytostatic agent in the two cell lines studied, but modulation of PKC is not involved in the mode of action by which it elicits this effect.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetamides*
  • Cell Division / drug effects
  • Cell Line / drug effects
  • Cytosol / drug effects
  • Cytosol / enzymology
  • Enzyme Activation / drug effects
  • Ethers, Cyclic / toxicity*
  • Humans
  • Marine Toxins / toxicity*
  • Protein Kinase C / antagonists & inhibitors
  • Protein Kinase C / physiology*
  • Pyrans*
  • Signal Transduction / drug effects
  • Spiro Compounds
  • Structure-Activity Relationship
  • Tetradecanoylphorbol Acetate / pharmacology
  • Tumor Cells, Cultured / drug effects

Substances

  • Acetamides
  • Ethers, Cyclic
  • Marine Toxins
  • Pyrans
  • Spiro Compounds
  • bistratene A
  • Protein Kinase C
  • Tetradecanoylphorbol Acetate