Combined MEK and JAK inhibition abrogates murine myeloproliferative neoplasm
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
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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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 2

NrasG12D/G12D hyperactivates ERK1/2 in HSCs, and downregulation of MEK/ERK signaling rescues NrasG12D/G12D HSC exhaustion.

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NrasG12D/G12D hyperactivates ERK1/2 in HSCs, and downregulation of MEK/...
Control and NrasG12D/G12D mice were treated with pI-pC and sacrificed on day 12. (A and B) CD150+CD41– cells (enriched for HSCs) and CD150–CD41– cells (enriched for MPPs) were sorted from Sca1+-enriched total BM cells. Sorted cells were serum and cytokine starved for 30 minutes at 37°C (A). IL-3 stimulation was performed for 10 minutes at 37°C after starvation (B). Levels of pERK1/2 and pAKT were measured using phosphospecific flow cytometry. HSCs (defined as [Lin CD48]–/locKit+ cells from sorted CD150+CD41– cells) and MPPs (defined as [Lin CD48]–/locKit+ cells from sorted CD150–CD41– cells) were gated for data analysis. To quantify the activation of ERK1/2, median intensities of pERK1/2 at different IL-3 concentrations are shown relative to the respective control cells at 0 ng/ml (assigned as 1). (C) Quantification of c-Myc and cell senescence–related genes in control and NrasG12D/G12D HSCs using qRT-PCR. (D) Quantification of BM spleen HSCs from control and NrasG12D/G12D mice treated with vehicle or AZD6244 for 7 days. (E) Single NrasG12D/G12D HSC genotyping after AZD6244 treatment. Data are mean ± SD. *P < 0.05; **P < 0.01; ***P < 0.001.