JAK1 and acute lymphoblastic leukemia: Furthermore, constitutive activity of a JAK1 mutant homologous to JAK2 V617F (JAK1 V658F) was also inhibited by the homologous JAK1 F595 mutation (F636A), suggesting that our results in JAK2 might be relevant for activation of JAK1 mutants recently identified in T-ALL [32], [33].