In this issue of Blood, Nakata et al demonstrate that hematopoietic-specific expression of a mutation in the E3 ubiquitin ligase Casitas B cell lymphoma (CBL) results in a disorder that recapitulates the key features of human chronic myelomonocytic leukemia (CMML). One of the challenges currently facing researchers studying CMML is the scarcity of faithful model systems to study disease pathogenesis and therapeutic response. Given the lack of curative therapy for most patients with CMML, there is a pressing need to develop improved preclinical models to inform mechanistic studies and drug development. Although genetically engineered murine models exist for the 3 most commonly mutated genes in CMML, SRSF2, TET2, and ASXL1, none of these models recapitulates the entire phenotypic spectrum of human CMML, including chronic elevation in monocytes, multilineage dysplasia, hypersensitivity to cytokines, and susceptibility to transformation to acute myeloid leukemia (AML).
