RSPO3 and chronic myelogenous leukemia, BCR-ABL1 positive: Recently, Salik et al. reported that R-Spondin-3 and Lgr4/GPR48 regulate self-renewal capacity in acute myelogenous leukemia (AML) stem cells in vivo [43], paralleling our finding that Lgr4/GPR48 is essential for the maintenance of CML stem cells in mice [14].