More recently, direct measurement of oxygen tension in leukemic BM was obtained in a BCR-ABL B-ALL mouse model by intravital fast scanning two-photon phosphorescence lifetime imaging microscopy, which showed that oxygen levels vary from the initial to the final stages of leukemia, with a transient increase in oxygen levels at intermediate leukemia burden, correlating with expansion of the vasculature network, and a later significant decrease of BM oxygenation as leukemia cellularity increased at disease end-stage (64). Here, ABL1 is linked to leukemia.