This study aimed to determine whether the multi-
kinase inhibitor
dasatinib would provide an effective
therapy for myeloproliferative diseases (MPDs) involving c-Cbl mutations. These mutations, which occur in the RING finger and linker domains, abolish the ability of c-Cbl to function as an
E3 ubiquitin ligase and downregulate activated
protein tyrosine kinases. Here we analyzed the effects of
dasatinib in a c-Cbl RING finger mutant mouse that develops an MPD with a phenotype similar to the human MPDs. The mice are characterized by enhanced
tyrosine kinase signaling resulting in an expansion of hematopoietic stem cells, multipotent progenitors and cells within the myeloid lineage. Since c-Cbl is a negative regulator of c-Kit and Src signaling we reasoned that
dasatinib, which targets these
kinases, would be an effective
therapy. Furthermore, two recent studies showed
dasatinib to be effective in inhibiting the in vitro growth of cells from
leukemia patients with c-Cbl RING finger and linker domain mutations. Surprisingly we found that
dasatinib did not provide an effective
therapy for c-Cbl RING finger mutant mice since it did not suppress any of the hematopoietic lineages that promote MPD development. Thus we conclude that
dasatinib may not be an appropriate
therapy for
leukemia patients with c-Cbl mutations. We did however find that
dasatinib caused a marked reduction of pre-B cells and immature B cells which correlated with a loss of Src activity. This study is therefore the first to provide a detailed characterization of in vivo effects of
dasatinib in a hematopoietic disorder that is driven by
protein tyrosine kinases other than BCR-ABL.