Flow cytometric characterization of acute leukemia reveals a distinctive “blast gate” of murine T-lymphoblastic leukemia/lymphoma

Immunophenotypic analysis using multiparameter flow cytometry is a crucial tool for diagnosing and managing acute leukemia. Mouse models, which have been integral to medical research for over a century, are especially valuable in leukemia research. However, immunophenotypic analysis of murine leukemia is often underreported in published studies, and blast gating for isolating blasts has been detailed in only a few cases. Moreover, there has been no comprehensive characterization of all types of murine acute leukemia in large cohorts using flow cytometry. In this study, we utilized flow cytometry to thoroughly characterize murine acute leukemia across a large cohort of mice. Our findings revealed that murine T-lymphoblastic leukemia/lymphoma (T-ALL) displays a distinct “blast gate” (CD45bright) with CD45/side scatter gating, which contrasts with the “blast gate” (CD45dim) observed in human T-ALL. Conversely, murine B-lymphoblastic leukemia and acute myeloid leukemia share the same blast region (CD45dim) as their human counterparts. Through blast cell gating, we detected the development of T-ALL in FLT3-ITD knock-in mice for the first time, with an incidence rate of 23%. These leukemic cells were selectively killed by the FLT3 inhibitors crenolanib and midostaurin in vitro. These findings suggest that FLT3-ITD may play a role in the pathogenesis of T-ALL and that FLT3-ITD inhibition could be a viable therapeutic option for patients with T-ALL. Our gating strategy for immunophenotypic analysis can be applied to leukemogenesis and preclinical gene therapy studies in mice, potentially enhancing the quality of such analyses.