Iron homeostasis is dysregulated in primary myelofibrosis (PMF), given the high prevalence of anemia, need for red blood cell (RBC) transfusions, and disease-associated inflammatory state. We measured plasma hepcidin levels in 203 consecutive PMF patients at the time of first referral; hepcidin levels were significantly higher as compared to healthy controls (P < 0.0001), and were correlated with hemoglobin of <10 g/dL, RBC transfusion requirement, serum ferritin of >500 mg/L, higher dynamic international prognostic scoring system (DIPSS)-plus risk category, the presence of circulating blasts, age of >65 years, and leukocyte count of <4 3 10 9 /L. Increased hepcidin levels predicted for inferior survival independent of six out of the eight DIPSS-plus prognostic parameters (hazard ratio [HR] 5 1.8; P 5 0.02), but not when RBC transfusion requirement, hemoglobin of <10 g/dL, or increased serum ferritin were included in the Cox model. Multivariable analysis that considered the four overlapping prognostic variables revealed that increased hepcidin (HR 5 1.9; P 5 0.03) and increased ferritin (HR 5 2.3; P 5 0.04), but not hemoglobin of <10 g/dL or RBC transfusion requirement, independently retained their significance for predicting survival. Accordingly, increased levels of both hepcidin and serum ferritin (seen in 29% of patients) predicted inferior survival independent of DIPSS-plus or increased inflammatory cytokine levels (HR 5 2.4; P 5 0.002), and could be considered in future prognostic models for PMF. Am. J.

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CD123 is the α-subunit of the interleukin-3 receptor; it represents a potential therapeutic target in systemic mastocytosis (SM) given its absent expression on normal/reactive mast cells (MCs) and aberrant expression on neoplastic MCs. We studied 58 SM patients to define CD123 expression patterns by immunohistochemistry and its clinical significance. Two hematopathologists independently scored bone marrow slides using predefined histologic parameters. In all, 23 patients had indolent SM (ISM), 10 aggressive SM (ASM), 23 SM with associated hematological neoplasm (SM-AHN) and 2 had mast cell leukemia (MCL). MC_CD123 expression was demonstrable in 37 (64%) cases; expression rates were 100%, 61%, 57% and 0% in ASM, ISM, SM-AHN and MCL, respectively (P=0.02). Focal proliferation of plasmacytoid dendritic cells (PDCs) around MC aggregates, suggesting a tumor-promoting role for PDCs, was noted in 44 (76%) cases, and was significantly higher in CD123-positive versus -negative cases (87% versus 50%, P=0.005). CD123 expression and its staining intensity had prognostic value in SM-chronic myelomonocytic leukemia and nonindolent SM patients, respectively. These observations suggest that targeting CD123 in SM may have direct (via MCs) and indirect (via PDCs) antitumor effects and clinical trials to that effect require laboratory correlative studies to address the observed target expression heterogeneity.

SummaryMomelotinib (a JAK1 and JAK2 inhibitor) induces both anaemia and spleen responses in myelofibrosis (MF). Momelotinib treatment-emergent peripheral neuropathy (TE-PN) was documented in 44 (44%) of 100 MF patients treated at our institution; median time of TE-PN onset was 32 weeks and duration 11 months. Improvement after drug dose reduction or discontinuation was documented in only two patients. TE-PN was significantly associated with treatment response (P = 0Á02) and longer survival (P = 0Á048) but significance was lost during multivariate analysis that included treatment duration. TE-PN did not correlate with initial or maximum momelotinib dose or previous treatment with JAK inhibitor or thalidomide.