CCL2 and acquired polycythemia vera: Importantly, the pattern of inflammatory gene, CCL2 expression did not significantly differ between Philadelphia-negative MPNs (PV and ET) in our study as PV and ET with MF grade 0–1 “prefibrotic” with relatively low CCL2 gene expression, suggesting minimal inflammatory burden compared to PMF and Post-PV/ET-MF with MF grade 2–3 “overtly fibrotic” with the highest CCL2 gene expression, suggesting the highest inflammatory burden.