An improved isoprenylcysteine carboxylmethyltransferase inhibitor induces cancer cell death and attenuates tumor growth in vivo

Cancer Biol Ther. 2014 Sep;15(9):1280-91. doi: 10.4161/cbt.29692. Epub 2014 Jun 27.


Inhibitors of isoprenylcysteine carboxylmethyltransferase (Icmt) are promising anti-cancer agents, as modification by Icmt is an essential component of the protein prenylation pathway for a group of proteins that includes Ras GTPases. Cysmethynil, a prototypical indole-based inhibitor of Icmt, effectively inhibits tumor cell growth. However, the physical properties of cysmethynil, such as its low aqueous solubility, make it a poor candidate for clinical development. A novel amino-derivative of cysmethynil with superior physical properties and marked improvement in efficacy, termed compound 8.12, has recently been reported. We report here that Icmt (-/-) mouse embryonic fibroblasts (MEFs) are much more resistant to compound 8.12-induced cell death than their wild-type counterparts, providing evidence that the anti-proliferative effects of this compound are mediated through an Icmt specific mechanism. Treatment of PC3 prostate and HepG2 liver cancer cells with compound 8.12 resulted in pre-lamin A accumulation and Ras delocalization from the plasma membrane, both expected outcomes from inhibition of the Icmt-catalyzed carboxylmethylation. Treatment with compound 8.12 induced cell cycle arrest, autophagy and cell death, and abolished anchorage-independent colony formation. Consistent with its greater in vitro efficacy, compound 8.12 inhibited tumor growth with greater potency than cysmethynil in a xenograft mouse model. Further, a drug combination study identified synergistic antitumor efficacy of compound 8.12 and the epithelial growth factor receptor (EGFR)-inhibitor gefitinib, possibly through enhancement of autophagy. This study establishes compound 8.12 as a pharmacological inhibitor of Icmt that is an attractive candidate for further preclinical and clinical development.

Keywords: Icmt; Ras; anti-proliferation; autophagy; compound 8.12; cysmethynil; gefitinib; synergy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antineoplastic Agents / pharmacology*
  • Antineoplastic Agents / therapeutic use
  • Apoptosis / drug effects*
  • Autophagy / drug effects
  • Cell Cycle Checkpoints / drug effects
  • Cell Line, Tumor
  • Cell Proliferation / drug effects*
  • Cell Survival / drug effects
  • Drug Synergism
  • ErbB Receptors / antagonists & inhibitors
  • Female
  • Gefitinib
  • Heterografts
  • Humans
  • Indoles / pharmacology*
  • Indoles / therapeutic use
  • Indoles / toxicity
  • Lamin Type A / metabolism
  • Liver Neoplasms / drug therapy
  • Liver Neoplasms / pathology*
  • Methylation
  • Mice, SCID
  • Oncogene Protein p21(ras) / metabolism
  • Protein Methyltransferases / antagonists & inhibitors*
  • Protein Methyltransferases / metabolism
  • Protein Prenylation
  • Pyrimidines / pharmacology*
  • Pyrimidines / therapeutic use
  • Pyrimidines / toxicity
  • Quinazolines / pharmacology


  • Antineoplastic Agents
  • Indoles
  • Lamin Type A
  • Pyrimidines
  • Quinazolines
  • cysmethynil
  • Protein Methyltransferases
  • protein-S-isoprenylcysteine O-methyltransferase
  • ErbB Receptors
  • Oncogene Protein p21(ras)
  • Gefitinib