BLK and acquired polycythemia vera: On the one hand, JAK2V617F downregulated expression of Blk (B lymphocyte kinase) in JAK2V617F-expressing Ba/F3 cells (Figure 1A) and upregulated expression of Alox5 in PV mice (Figure 1B), and on the other hand, BCR-ABL also upregulates Alox5 expression [15] and did so through c-Myc (Figure 2A) and Blk (Figure 2B,C).