TNFα mRNA correlates with JAK2 kinase activity. (A) TNFα plasma concentration was evaluated in 48 MPN patients (16 PV, 7 ET, 25 MF) and 10 normal controls. Each data point represents a patient. Median TNFα concentration is shown as a bar. Detailed patient information including JAK2^V617F status is provided in supplemental Table 1 (available on the Blood Web site, see the Supplemental Materials link at the online article). (B) qRT-PCR analysis of median TNFα mRNA expression of Peripheral blood leukocytes from 43 PV patients and 21 normal controls. Median TNFα expression in cells from normal controls was normalized to 1. (C) Correlation between JAK2^V617F allele burden and TNF plasma concentration. Allele burden was determined in 20 JAK2^V617F-positive patients by real-time quanitative PCR and correlated with TNF plasma concentration. (D) TNFα mRNA expression was analyzed by qRT-PCR in human hematopoietic cell lines and normalized to GAPDH. The TNFα expression in HEL cells was arbitrarily set to 1 and results for the other lines are shown in comparison. (E-F) TNFα mRNA expression after pharmacologic inhibition of JAK2, (E) HEL (left) and HL60 (right) cells treated with JAK2 inhibitor CYT387, (F) primary human blood MNCs treated with CYT387.