Figure 8. IL-33/ST2 signaling promotes MPN development.

(A) Indicated JAK2^V617F+ cell lines were incubated for 24 hours ± IL-33, and expression levels were measured for the transcripts of the indicated genes. Mean expression levels of technical duplicates are represented as fold induction and have been normalized to conditions without IL-33. (B) The MPN cell lines SET-2 and HEL were cultured ± IL-33, and percentage of live cells (annexin V^– DAPI^–) was assessed at the indicated time points. Results show means ± SEM. (C) Relative median fluorescence intensity (MFI) of ST2 expression on blood CD34⁺ stem/progenitor cells from MPNs (PMF [n = 3], PV [n = 5], and after ET/PV myelofibrosis [n = 3]) and control (n = 5) donors. (D) Representative histograms showing ST2 expression on blood CD34⁺ stem/progenitor cells from the indicated donors. (E) Colony formation assay (CFA) from MACS-purified blood CD34⁺ stem/progenitor cells from controls and MPN patients cultured in standard CFC medium ± IL-33 for 2 weeks. Data are mean ± SEM and show fold changes in colony numbers after normalization to conditions without IL-33. Healthy (n = 5) and 10 MPN donors were used. (A) One representative of 2 independent experiments, and (B) pooled values from 3 individual experiments are shown. (C and D) Pooled data from 2 independent experiments are shown. (B) Standard Student’s t test, (C) Standard Student’s t test with Welch’s correction, and (D) Wilcoxon signed-rank test were used. *P < 0.05; **P < 0.01.