Upregulation of IGF1R by mutant RAS in leukemia and potentiation of RAS signaling inhibitors by small-molecule inhibition of IGF1R

Clin Cancer Res. 2014 Nov 1;20(21):5483-95. doi: 10.1158/1078-0432.CCR-14-0902. Epub 2014 Sep 3.

Abstract

Purpose: Activating mutations in the RAS oncogene occur frequently in human leukemias. Direct targeting of RAS has proven to be challenging, although targeting of downstream RAS mediators, such as MEK, is currently being tested clinically. Given the complexity of RAS signaling, it is likely that combinations of targeted agents will be more effective than single agents.

Experimental design: A chemical screen using RAS-dependent leukemia cells was developed to identify compounds with unanticipated activity in the presence of an MEK inhibitor and led to identification of inhibitors of IGF1R. Results were validated using cell-based proliferation, apoptosis, cell-cycle, and gene knockdown assays; immunoprecipitation and immunoblotting; and a noninvasive in vivo bioluminescence model of acute myeloid leukemia (AML).

Results: Mechanistically, IGF1R protein expression/activity was substantially increased in mutant RAS-expressing cells, and suppression of RAS led to decreases in IGF1R. Synergy between MEK and IGF1R inhibitors correlated with induction of apoptosis, inhibition of cell-cycle progression, and decreased phospho-S6 and phospho-4E-BP1. In vivo, NSG mice tail veins injected with OCI-AML3-luc+ cells showed significantly lower tumor burden following 1 week of daily oral administration of 50 mg/kg NVP-AEW541 (IGF1R inhibitor) combined with 25 mg/kg AZD6244 (MEK inhibitor), as compared with mice treated with either agent alone. Drug combination effects observed in cell-based assays were generalized to additional mutant RAS-positive neoplasms.

Conclusions: The finding that downstream inhibitors of RAS signaling and IGF1R inhibitors have synergistic activity warrants further clinical investigation of IGF1R and RAS signaling inhibition as a potential treatment strategy for RAS-driven malignancies.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Apoptosis / drug effects
  • Apoptosis / genetics
  • Benzimidazoles / pharmacology
  • Cell Cycle / drug effects
  • Cell Cycle / genetics
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Cell Proliferation / genetics
  • Female
  • Genes, ras / genetics*
  • Humans
  • Leukemia, Myeloid, Acute / drug therapy
  • Leukemia, Myeloid, Acute / genetics*
  • Mice
  • Mitogen-Activated Protein Kinase Kinases / genetics
  • Pyrimidines / pharmacology
  • Pyrroles / pharmacology
  • Receptor, IGF Type 1 / antagonists & inhibitors*
  • Receptor, IGF Type 1 / genetics*
  • Signal Transduction / drug effects*
  • Signal Transduction / genetics
  • Small Molecule Libraries / pharmacology*
  • Up-Regulation / genetics*

Substances

  • AZD 6244
  • Benzimidazoles
  • NVP-AEW541
  • Pyrimidines
  • Pyrroles
  • Small Molecule Libraries
  • Receptor, IGF Type 1
  • Mitogen-Activated Protein Kinase Kinases