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Characterize Disease-related Mutants of RAF Family Kinases by Using a Set of Practical and Feasible Methods
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Response and resistance to MEK inhibition in leukaemias initiated by hyperactive Ras

Jennifer O Lauchle1, Doris Kim, Doan T Le

  • 1Department of Pediatrics, University of California, San Francisco, California 94143, USA.

Nature
|September 4, 2009
PubMed

Insights

MEK inhibitors show promise for Nf1-deficient acute myeloid leukaemias (AMLs) but not myeloproliferative disorders (MPDs). Resistance mechanisms involve specific gene mutations, offering insights into targeted cancer therapy.

Area of Science:

  • Oncology
  • Molecular Biology
  • Cancer Genetics

Background:

  • The Raf/MEK/ERK pathway is a key target in cancers with Ras pathway dysregulation, including those with Nf1 inactivation.
  • Nf1 encodes neurofibromin, a GTPase-activating protein that negatively regulates Ras signaling.
  • Targeting MEK offers a potential therapeutic strategy for Nf1-deficient cancers.

Purpose of the Study:

  • To evaluate the efficacy of MEK inhibitors in Nf1-deficient myeloproliferative disorders (MPDs) and acute myeloid leukaemias (AMLs).
  • To identify mechanisms of de novo and acquired resistance to MEK inhibitors in these cancers.
  • To explore strategies for overcoming drug resistance in Nf1-mutant cancers.

Main Methods:

  • Comparison of MEK inhibitor effects in mouse models of Nf1-deficient MPD and AML.
  • Induction of cooperating mutations in AML using retroviral insertional mutagenesis.
  • Cloning of retroviral integrations to identify resistance genes and functional analysis of identified pathways.

Main Results:

  • MEK inhibitors were ineffective in Nf1-deficient MPDs.
  • MEK inhibitors induced objective regression in a significant proportion of Nf1-deficient AMLs.
  • Drug resistance arose from pre-existing AML clones, with identified resistance genes including Rasgrp1, Rasgrp4, and Mapk14 (p38alpha).
  • Increased RasGRP1 levels and reduced p38 kinase activity were implicated in resistance.

Conclusions:

  • MEK inhibitors demonstrate differential efficacy in Nf1-deficient hematologic malignancies.
  • Understanding resistance mechanisms, such as those involving RasGRP1 and p38alpha, is crucial for developing effective therapeutic strategies.
  • This study provides a framework for identifying genes and pathways that influence response to targeted therapies and resistance in primary cancer cells.

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