As the transcriptome analysis emphasized the central role for alarmins S100a8/S100a9 in the tasquinimod‐mediated effect on fibrosis and the MPN phenotype, we next sought to systematically dissect the effect of S100a9 (and S100a8) knockout (1) in the stroma and (2) in hematopoietic cells on the fibrotic transformation. Here, S100A9 is linked to myeloproliferative neoplasm.