Clavilactones, a novel class of tyrosine kinase inhibitors of fungal origin

Biochem Pharmacol. 2000 Jun 15;59(12):1539-47. doi: 10.1016/s0006-2952(00)00278-1.


Targeting of deregulated protein tyrosine kinases has been proposed as a new approach in the therapeutic intervention against pathological processes including proliferative disorders and cancer. Using a screening approach based on a comparative evaluation of antiproliferative effects in a panel of tumor cells with differential expression of protein tyrosine kinases, three benzoquinoid macrolidic fungal metabolites produced by Clitocybe clavipes, clavilactones A, B, and D (CA, CB, and CD) and two semisynthetic derivatives of these products, diacetyl-CA and dimethyl-CA, were identified as inhibitors of protein tyrosine kinases. Naturally occurring CA, CB, and CD showed inhibitory activity in kinase assays against the Ret/ptc1 and epidermal growth factor receptor (EGF-R) tyrosine kinases, while being less effective against the v-Abl tyrosine kinase and p34(cdc2) serine/threonine kinase (IC(50) 2.8, 5.5, 81.3, and 128 microM respectively, for the most potent compound CD). CB was shown to be a non-competitive inhibitor of EGF-R with respect to ATP or poly(Glu(6)Ala(3)Tyr). CD also preferentially inhibited the growth of A431 cells, which overexpress a constitutively active EGF-R, as opposed to IGROV-1 and SKOV-3 cells, which express low levels of the receptor. Further, EGF-R was shown to be a target for clavilactones in A431 cells, since EGF-induced receptor autophosphorylation was inhibited in the presence of CB, CD, and diacetyl-CA. Both CD and diacetyl-CA displayed weak activity when administered daily (i.p.) to mice bearing ascitic A431 tumor. These findings indicate that clavilactones represent the prototypes of a new structural class of tyrosine kinase inhibitors deserving further investigation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Agaricales / chemistry*
  • Animals
  • Antineoplastic Agents / pharmacology*
  • Antineoplastic Agents / therapeutic use
  • Cell Division / drug effects
  • Cell Line, Transformed
  • Disease Models, Animal
  • Enzyme Inhibitors / pharmacology*
  • Enzyme Inhibitors / therapeutic use
  • ErbB Receptors / metabolism
  • Humans
  • Lactones / pharmacology*
  • Lactones / therapeutic use
  • Macrolides / pharmacology*
  • Macrolides / therapeutic use
  • Mice
  • Mice, Nude
  • Neoplasms, Experimental / drug therapy
  • Phosphorylation
  • Protein Kinases / metabolism
  • Protein-Tyrosine Kinases / antagonists & inhibitors*
  • Tumor Cells, Cultured


  • Antineoplastic Agents
  • Enzyme Inhibitors
  • Lactones
  • Macrolides
  • Protein Kinases
  • ErbB Receptors
  • Protein-Tyrosine Kinases