In vitro and in vivo effects of JAK 2 inhibition in chronic myelomonocytic leukemia

• Published in: European journal of haematology Vol. 97; no. 6; pp. 562 - 567
• Main Authors: Geissler, Klaus, Jäger, Eva, Barna, Agnes, Sliwa, Thamer, Knöbl, Paul, Schwarzinger, Ilse, Gisslinger, Heinz, Valent, Peter
• Format: Journal Article
• Language: English
• Published: 01.12.2016
• ISSN: 0902-4441; 1600-0609
• DOI: 10.1111/ejh.12773

Abstract In chronic myelomonocytic leukemia ( CMML ), colony‐forming units granulocyte/macrophage ( CFU ‐ GM ), which grow in vitro in the absence of exogenous growth factors, arise from the abnormal clone that is responsible for the overproduction of granulomonocytic cells. Previous in vitro findings including ours suggest that divergent molecular aberrations in CMML seem to converge within the GM ‐ CSF signaling pathway. As JAK 2 is a sentinel kinase in this pathway, JAK 2 inhibition may be an attractive treatment approach in CMML . We investigated the in vitro effects of the specific JAK 2 inhibitor TG 101209 on the autonomous CFU ‐ GM formation from peripheral blood mononuclear cells of patients with CMML . TG 101209 was found to either block or strongly inhibit spontaneous CFU ‐ GM growth in all 10 patients tested. This inhibitory effect was dose dependent and significantly more pronounced as compared to the inhibitory effect on stimulated CFU ‐ GM growth from normal individuals. In a CMML patient with splenomegaly, who was treated with the JAK 1/2 inhibitor ruxolitinib off label, we can demonstrate a spleen response and the disappearance of constitutional symptoms which was associated with a decrease in autonomous CFU ‐ GM formation ex vivo . Pharmacological JAK 2 inhibition may be an interesting approach to be systematically studied in patients with CMML .