Inactivation of Ret/Ptc1 oncoprotein and inhibition of papillary thyroid carcinoma cell proliferation by indolinone RPI-1

Cell Mol Life Sci. 2003 Jul;60(7):1449-59. doi: 10.1007/s00018-003-2381-8.


Genetic alterations causing oncogenic activation of the RET gene are recognized as pathogenic events in papillary and medullary thyroid carcinomas. Inhibition of Ret oncoprotein functions could thereby represent a specific therapeutic approach. We previously described the inhibitory activity of the 2-indolinone derivative RPI-1 (formerly Cpdl) on the tyrosine kinase activity and transforming ability of the products of the RET/PTC1 oncogene exogenously expressed in murine cells. In the present study, we investigated the effects of RPI-1 in the human papillary thyroid carcinoma cell line TPC-1 spontaneously harboring the RET/PTC1 rearrangement. Treatment with RPI-1 inhibited cell proliferation and induced accumulation of cells at the G2 cell cycle phase. In treated cells, Ret/Ptc1 tyrosine phosphorylation was abolished along with its binding to Shc and phospholipase C(gamma), thereby indicating abrogation of constitutive signaling mediated by the oncoprotein. Activation of JNK2 and AKT was abolished, thus supporting the drug inhibitory efficacy on downstream pathways. In addition, cell growth inhibition was associated with a reduction in telomerase activity by nearly 85%. These findings in a cellular context relevant to the pathological function of RET oncogenes support the role of Ret oncoproteins as useful targets for therapeutic intervention, and suggest RPI-1 as a promising candidate for preclinical development in the treatment of thyroid tumors expressing RET oncogenes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Carcinoma, Papillary / pathology*
  • Cell Cycle / drug effects
  • Cell Division / drug effects*
  • DNA, Neoplasm / drug effects
  • DNA, Neoplasm / genetics
  • Humans
  • Indoles / pharmacology*
  • Intracellular Signaling Peptides and Proteins
  • Kinetics
  • Membrane Proteins
  • Mice
  • Oncogene Proteins / antagonists & inhibitors*
  • Oncogene Proteins, Fusion
  • Patched Receptors
  • Patched-1 Receptor
  • Protein-Tyrosine Kinases
  • Proteins*
  • Proto-Oncogene Proteins c-ret
  • Receptor Protein-Tyrosine Kinases / antagonists & inhibitors*
  • Receptors, Cell Surface
  • Reverse Transcriptase Polymerase Chain Reaction
  • Signal Transduction / drug effects
  • Signal Transduction / physiology
  • Telomerase / genetics
  • Thyroid Neoplasms / pathology*
  • Tumor Cells, Cultured


  • DNA, Neoplasm
  • Indoles
  • Intracellular Signaling Peptides and Proteins
  • Membrane Proteins
  • Oncogene Proteins
  • Oncogene Proteins, Fusion
  • Patched Receptors
  • Patched-1 Receptor
  • Proteins
  • Ptch1 protein, mouse
  • RPI-1 compound
  • Receptors, Cell Surface
  • Protein-Tyrosine Kinases
  • Proto-Oncogene Proteins c-ret
  • RET protein, human
  • Receptor Protein-Tyrosine Kinases
  • Ret-Ptc1 oncoprotein, mouse
  • ret-PTC fusion oncoproteins, human
  • Telomerase