PTPA and chronic myelogenous leukemia, BCR-ABL1 positive: Because IB inhibits NADPH oxidase, we sought to investigate whether IB-induced apoptosis of CML stem/progenitor cells depends, at least in part, on inhibition of PP2A tumor suppressor activity as we previously reported in both TKI-resistant quiescent stem and progenitor cells from CML-CP and -BC patients [7, 19].