A Unique Signaling Feedback Circuit Defines Interferon Responses in Myeloproliferative Neoplasms
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ABSTRACT: Type I interferons (IFNs) are key initiators and effectors of the immune response against malignant cells and can also directly inhibit tumor growth. IFN is highly effective in the treatment of myeloproliferative neoplasms (MPNs), but the mechanisms of action are unclear and it remains unknown why some patients respond to IFN therapy and others do not. We have identified and characterized a novel pathway involving PKC upstream of the kinase ULK1. Engagement of the Type I IFN receptor triggers PKC-dependent phosphorylation of ULK1 on serines 341 and 495, required for subsequent engagement of p38 MAPK that regulates transcription of IFN-stimulated genes and subsequent growth inhibitory responses. We show that this pathway is essential for IFN-suppressive effects on primary malignant erythroid precursors from patients with MPNs in vitro, while increased levels of ULK1 and p38 MAPK correlate with clinical response to IFN therapy in MPN patients. IFN treatment also induces cleavage/activation of the ULK1-interacting ROCK1/2 proteins in vivo, triggering a negative feedback loop that suppresses IFN responses. Both ROCK homologs are overexpressed in MPN patients and their genetic or pharmacological inhibition enhances IFN-anti-neoplastic responses in malignant erythroid progenitors from MPN patients. Together, our results identify activation of the PKC-ULK1-p38 MAPK cascade as a key and essential component for the IFN-response, regulated by a feedback loop involving ROCK1/2. These findings suggest the clinical potential of pharmacological inhibition of ROCK1/2 in combination with IFN-therapy for the treatment of MPN patients.
INSTRUMENT(S): LTQ Orbitrap Velos
ORGANISM(S): Homo Sapiens (human)
TISSUE(S): Cell Culture
SUBMITTER: Paul Thomas
LAB HEAD: Leonidas C. Platanias
PROVIDER: PXD021748 | Pride | 2022-01-10
REPOSITORIES: Pride
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