JAK2 and acute lymphoblastic leukemia: Contrary to the TYK2-rearrangement B-ALL model of Tavakoli Shirazi P et al. (2021), another study investigating the effect of long-term exposure to ruxolitinib in CRLF2-r/JAK2 mutated B-ALL suggests that adaptation to prolonged JAK2 inhibition is due to c-MYC expression rather than persistent JAK/STAT signaling activation.