JAK1 and acute lymphoblastic leukemia: Approximately 50% of Ph-like ALL patients harbor CRLF2r, and roughly half of these patients also harbor activating point mutations in JAK1 or JAK2 (Table 1) (Mullighan et al., 2009a; Mullighan et al., 2009c; Russell et al., 2009; Pui et al., 2017; Reshmi et al., 2017).