Abstract
BackgroundAbl interactor 1 (Abi1) is a downstream target of Abl tyrosine kinases and a component of the WAVE regulatory complex (WRC) that plays an important role in regulating actin cytoskeleton remodeling and membrane receptor signaling. While studies using short hairpin RNA (shRNA) have suggested that Abi1 plays a critical role in Bcr-Abl-induced leukemogenesis, the mechanism involved is not clear.MethodsIn this study, we knocked out Abi1 expression in p185Bcr-Abl-transformed hematopoietic cells using CRISPR/Cas9-mediated gene editing technology. The effects of Abi1 deficiency on actin cytoskeleton remodeling, the Bcr-Abl signaling, IL-3 independent growth, and SDF-induced chemotaxis in these cells were examined by various in vitro assays. The leukemogenic activity of these cells was evaluated by a syngeneic mouse transplantation model.ResultsWe show here that Abi1 deficiency reduced the IL3-independent growth and SDF-1α-mediated chemotaxis in p185Bcr-Abl-transformed hematopoietic cells and inhibited Bcr-Abl-induced abnormal actin remodeling. Depletion of Abi1 also impaired the Bcr-Abl signaling to the ERK and PI3 kinase/Akt pathways. Remarkably, the p185Bcr-Abl-transformed cells with Abi1 deficiency lost their ability to develop leukemia in syngeneic mice. Even though these cells developed drug tolerance in vitro after prolonged selection with imatinib as their parental cells, the imatinib-tolerant cells remain incapable of leukemogenesis in vivo.ConclusionsTogether, this study highlights an essential role of Abi1 in Bcr-Abl-induced leukemogenesis and provides a model system for dissecting the Abi1 signaling in Bcr-Abl-positive leukemia.
Highlights
Abl interactor 1 (Abi1) is a downstream target of Abl tyrosine kinases and a component of the WASP-family verprolin-homologous (WAVE) regulatory complex (WRC) that plays an important role in regulating actin cytoskeleton remodeling and membrane receptor signaling
Depending on the amount of breakpoint cluster region (Bcr) sequences fused, three different Bcr-Abl fusion proteins may be produced with molecular masses of 185 kilodalton (Kd) (p185Bcr-Abl), 210 Kd (p210Bcr-Abl), and 230 Kd (p230Bcr-Abl) [1,2,3]. p210Bcr-Abl expression is a causative event in over 95% of human chronic myelogenous leukemia (CML) cases, while p185Bcr-Abl is found in 60–80% of Phpositive B cell acute lymphocytic leukemia (Ph+ B-ALL)
CRISPR/Cas9-mediated Abi1 gene editing in p185Bcr-Abltransformed Ba/F3 cells To determine the role of Abi1 in Bcr-Abl-induced cellular transformation and leukemogenesis, we used CRISPR/
Summary
Abl interactor 1 (Abi1) is a downstream target of Abl tyrosine kinases and a component of the WAVE regulatory complex (WRC) that plays an important role in regulating actin cytoskeleton remodeling and membrane receptor signaling. We have shown that the knockdown of Abi expression by sequence-specific small hairpin RNA (shRNA) inhibited p185Bcr-Abl-stimulated cell adhesion and migration in vitro and impaired p185Bcr-Abl-induced leukemogenesis in vivo [30, 31]. In these studies, the leukemogenesis was delayed but not eliminated, possibly due to incomplete Abi depletion [30]. The complete depletion of Abi inhibits Bcr-Abl-induced abnormal actin polymerization, cell proliferation, and cell migration in vitro, and inhibits leukemogenesis in vivo. The inhibition of Bcr-Abl-induced leukemia by Abi deficiency is independent of the sensitivity of these cells to imatinib, as the imatinib-tolerant p185Bcr-Abl cells require Abi for development of leukemia in vivo
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