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A Unique Signaling Feedback Circuit Defines Interferon Responses in Myeloproliferative Neoplasms

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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Project description:Interferon (IFN)-alpha causes high rates of depression and fatigue, and is used to investigate the impact of innate immune cytokines on brain and behavior. However, little is known about transcriptional profiles of circulating immune cells during chronic IFN-alpha administration. Accordingly, genome-wide transcriptional profiling was performed on peripheral blood mononuclear cells from 21 patients with chronic hepatitis C virus either awaiting IFN-alpha therapy (n=10) or after 12 weeks of IFN-alpha treatment (n=11). Significance analysis of microarray data identified 252 up-regulated gene transcripts, the majority of which were related to IFN-alpha/antiviral or innate-immune/inflammatory signaling. Of these upregulated genes, 2'-5'-oligoadenylate synthetase 2 (OAS2) was the only gene that was differentially expressed in patients that developed IFN-alpha-induced depression/fatigue, and correlated with depression and fatigue scores at 12 weeks of IFN-alpha administration. Promoter-based bioinformatic and cellular origin analyses revealed IFN-alpha-induced increases in genes bearing transcription factor binding motifs (TFBMs) related to myeloid differentiation, IFN-alpha signaling, API and CREB/ATF family of transcription pathways, with changes derived primarily from monocytes and plasmacytoid dendritic cells. Patients with high depression/fatigue scores demonstrated up-regulation of genes bearing TFBMs for myeloid differentiation, IFN-alpha and AP1 signaling, and down regulation of TFBMs for CREB/ATF-related transcription factors. Cellular origin analyses indicated a shift toward genes derived from CD8+T and NK cells in subjects with high depression/fatigue scores. These results reveal an antiviral and inflammatory transcriptional profile after 12 weeks IFN-alpha, accompanied by increased OAS2 expression, decreased CREB/ATF transcriptional control, and a shift from monocyte-derived genes to those of cytotoxic lymphocytes in IFN-alpha-induced depression/fatigue. Total RNA was isolated from the peripheral blood mononuclear cells (PBMC) obtained at 12 weeks from HCV patients treated with IFN-alpha plus ribavirin (n=11) and untreated HCV patients awaiting IFN-alpha/ribavirin therapy (control subjects, n=10).

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A Unique Signaling Feedback Circuit Defines Interferon Responses in Myeloproliferative Neoplasms

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