Combined MEK and JAK inhibition abrogates murine myeloproliferative neoplasm
Guangyao Kong, … , James C. Mulloy, Jing Zhang
Guangyao Kong, … , James C. Mulloy, Jing Zhang
Published May 8, 2014
Citation Information: J Clin Invest. 2014;124(6):2762-2773. https://doi.org/10.1172/JCI74182.
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Research Article Hematology

Combined MEK and JAK inhibition abrogates murine myeloproliferative neoplasm

Abstract

Overactive RAS signaling is prevalent in juvenile myelomonocytic leukemia (JMML) and the myeloproliferative variant of chronic myelomonocytic leukemia (MP-CMML) in humans, and both are refractory to conventional chemotherapy. Conditional activation of a constitutively active oncogenic Nras (NrasG12D/G12D) in murine hematopoietic cells promotes an acute myeloproliferative neoplasm (MPN) that recapitulates many features of JMML and MP-CMML. We found that NrasG12D/G12D-expressing HSCs, which serve as JMML/MP-CMML–initiating cells, show strong hyperactivation of ERK1/2, promoting hyperproliferation and depletion of HSCs and expansion of downstream progenitors. Inhibition of the MEK pathway alone prolonged the presence of NrasG12D/G12D-expressing HSCs but failed to restore their proper function. Consequently, approximately 60% of NrasG12D/G12D mice treated with MEK inhibitor alone died within 20 weeks, and the remaining animals continued to display JMML/MP-CMML–like phenotypes. In contrast, combined inhibition of MEK and JAK/STAT signaling, which is commonly hyperactivated in human and mouse CMML, potently inhibited human and mouse CMML cell growth in vitro, rescued mutant NrasG12D/G12D-expressing HSC function in vivo, and promoted long-term survival without evident disease manifestation in NrasG12D/G12D animals. These results provide a strong rationale for further exploration of combined targeting of MEK/ERK and JAK/STAT in treating patients with JMML and MP-CMML.

Authors

Guangyao Kong, Mark Wunderlich, David Yang, Erik A. Ranheim, Ken H. Young, Jinyong Wang, Yuan-I Chang, Juan Du, Yangang Liu, Sin Ruow Tey, Xinmin Zhang, Mark Juckett, Ryan Mattison, Alisa Damnernsawad, Jingfang Zhang, James C. Mulloy, Jing Zhang

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Figure 3

Combined inhibition of JAK and MEK effectively blocks the growth of human and mouse JMML/MP-CMML cells in vitro.

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Combined inhibition of JAK and MEK effectively blocks the growth of huma...
(A) WBM cells from moribund NrasG12D/G12D or KrasG12D/+ mice with advanced JMML/MP-CMML were serum and cytokine starved for 90 minutes at 37°C and incubated with DMSO vehicle or drugs for another 30 minutes at 37°C. Cells were then stimulated with 10 ng/ml GM-CSF or SCF for 10 minutes at 37°C. Levels of pERK1/2, pSTAT5, and pAKT were measured using phosphospecific flow cytometry. Non-neutrophil Lin–cKit+ cells were gated for data analysis. Shown are results of 1 representative experiment. (B and C) BM cells from moribund NrasG12D/G12D, NrasG12D/+, and KrasG12D/+ mice with advanced JMML/MP-CMML (B) and from human MP-CMML patients (C; n = 5) were cultured in triplicate in 96-well plates in the presence of vehicle or various concentrations of AZD6244 and/or AZD1480 for 5–14 days. Cell number was quantified by CellTiter-Glo assay. Data are mean ± SD.