Activated granulocytes and inflammatory cytokine signaling drive T-cell lymphoma progression and disease symptoms.

Peripheral T-cell lymphomas (PTCLs), especially angioimmunoblastic and follicular TCLs, have a dismal prognosis because of the lack of efficient therapies, and patients' symptoms are often dominated by an inflammatory phenotype, including fever, night sweats, weight loss, and skin rash. In this study, we investigated the role of inflammatory granulocytes and activated cytokine signaling on T-cell follicular helper-type PTCL (TFH-PTCL) disease progression and symptoms. We showed that ITK-SYK-driven murine PTCLs and primary human TFH-PTCL xenografts both induced inflammation in mice, including murine neutrophil expansion and massive cytokine release. Granulocyte/lymphoma interactions were mediated by positive autoregulatory cytokine loops involving interferon gamma (CD4+ malignant T cells) and interleukin 6 (IL-6; activated granulocytes), ultimately inducing broad JAK activation (JAK1/2/3 and TYK2) in both cell types. Inflammatory granulocyte depletion via antibodies (Ly6G), genetic granulocyte depletion (LyzM-Cre/MCL1flox/flox), or IL-6 deletion within microenvironmental cells blocked inflammatory symptoms, reduced lymphoma infiltration, and enhanced mouse survival. Furthermore, unselective JAK inhibitors (ruxolitinib) inhibited both TCL progression and granulocyte activation in various PTCL mouse models. Our results support the important role of granulocyte-driven inflammation, cytokine-induced granulocyte/CD4+ TCL interactions, and an intact JAK/STAT signaling pathway for TFH-PTCL development and also support broad JAK inhibition as an effective treatment strategy in early disease stages.

LSD1 Inhibition Prolongs Survival in Mouse Models of MPN by Selectively Targeting the Disease Clone.

Despite recent advances, the myeloproliferative neoplasms (MPNs) are attended by considerable morbidity and mortality. Janus kinase (Jak) inhibitors such as ruxolitinib manage symptoms but do not substantially change the natural history of the disease. In this report, we show the effects of IMG-7289, an irreversible inhibitor of the epigenetically active lysine-specific demethylase 1 (LSD1) in mouse models of MPN. Once-daily treatment with IMG-7289 normalized or improved blood cell counts, reduced spleen volumes, restored normal splenic architecture, and reduced bone marrow fibrosis. Most importantly, LSD1 inhibition lowered mutant allele burden and improved survival. IMG-7289 selectively inhibited proliferation and induced apoptosis of JAK2 V617F cells by concomitantly increasing expression and methylation of p53, and, independently, the pro-apoptotic factor PUMA and by decreasing the levels of its antiapoptotic antagonist BCLXL. These data provide a molecular understanding of the disease-modifying activity of the LSD1 inhibitor IMG-7289 that is currently undergoing clinical evaluation in patients with high-risk myelofibrosis. Moreover, low doses of IMG-7289 and ruxolitinib synergize in normalizing the MPN phenotype in mice, offering a rationale for investigating combination therapy.