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Updated: May 14, 2026

A Method for Screening and Validation of Resistant Mutations Against Kinase Inhibitors
12:40

A Method for Screening and Validation of Resistant Mutations Against Kinase Inhibitors

Published on: December 7, 2014

Intrinsic resistance to JAK2 inhibition in myelofibrosis

Anna Kalota1, Grace R Jeschke, Martin Carroll

  • 1Division of Hematology and Oncology, University of Pennsylvania, Philadelphia, PA 19104, USA.

Clinical Cancer Research : an Official Journal of the American Association for Cancer Research
|February 7, 2013
PubMed
Abstract

Insights

Myelofibrosis patients show intrinsic resistance to JAK2 inhibitors, suggesting mechanisms upstream of STAT3/STAT5. This study developed an in vitro assay to evaluate JAK2 inhibition effectiveness in myeloproliferative neoplasms.

Area of Science:

  • Hematology
  • Oncology
  • Pharmacology

Background:

  • Myeloproliferative neoplasms (MPN) are linked to Janus-activated kinase (JAK)2 activation.
  • Current JAK2 inhibitors lack selectivity and their clinical efficacy in inhibiting JAK2 activity requires rigorous evaluation.

Purpose of the Study:

  • To develop an in vitro assay for assessing JAK2 inhibition efficacy in MPN patient samples.
  • To investigate mechanisms of resistance to JAK2 inhibitors in MPN.

Main Methods:

  • Primary cells from MPN patients and normal donors were treated with JAK2 inhibitors.
  • Phosphorylation of downstream targets STAT5 and STAT3 was measured by flow cytometry.
  • Results were correlated with JAK2 V617F allele burden and plasma cytokine levels.

Main Results:

  • A dose-dependent decrease in pSTAT5 and pSTAT3 was observed in treated granulocytes.
  • Cells from myelofibrosis patients exhibited significantly less inhibition of pSTAT3 and pSTAT5 compared to other MPN subtypes and normal donors.
  • Resistance did not correlate with JAK2 V617F allele burden or plasma cytokine levels.

Conclusions:

  • Cell-intrinsic mechanisms confer resistance to JAK2 inhibition in myelofibrosis.
  • These resistance mechanisms are located upstream of STAT3 and STAT5 signaling pathways.

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