Dasatinib Targets B-Lineage Cells but Does Not Provide an Effective Therapy for Myeloproliferative Disease in c-Cbl RING Finger Mutant Mice

Abstract

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.

Casitas B-cell lymphoma (Cbl) proteins protect mammary epithelial cells from proteotoxicity of active c-Src accumulation

“…However, if cells successfully up-regulate chaperones or activate alternative pathways to clear accumulated active tyrosine kinases, such cells may survive and gain growth advantage. This model is consistent with paradoxical observations that treatment with dasatinib or a BCR-ABL inhibitor imatinib aggravated the myeloproliferative disease phenotype of Cbl RING finger mutant (44) or MMTV-Cre;Cbl flox ;Cblb del mice (45), respectively. Clearly, limiting the tyrosine kinase activation promotes proliferation of hematopoietic cells in the absence of Cbl activity.…”

Acquired expression of CblQ367P in mice induces dysplastic myelopoiesis mimicking chronic myelomonocytic leukemia

“…However, although application of Dasatinib, a TKI, to Cbl C379A/2 knockin mice suppressed the number of WBCs, the decreased cells were mainly B lymphocytes, and no apparent effect was observed in the myeloid and HSC populations. 49 In our study, administration of Dasatinib to Cbl Q367P mice did not decrease, but occasionally increased, the WBC number, including myeloid cells (data not shown). These findings strongly suggest that dasatinib treatment is not effective for eradicating CMML cells expressing mutant CBL.…”

CBL family E3 ubiquitin ligases control JAK2 ubiquitination and stability in hematopoietic stem cells and myeloid malignancies

“…Of note, inhibitors to two known CBL targets in hematopoietic cells, KIT and FLT3, have been tested in the RF knock-in Cbl C379A/− mice that develop a similar disease but with a longer latency (Rathinam et al 2010). While the FLT3 inhibitor (FLT3i) quizartinib temporarily alleviated CMML development in this model, the c-Kit/Src inhibitor dasatinib failed to impact the disease in Cbl C379A/− mice (Taylor et al 2012;Duyvestyn et al 2014). Based on our new findings, we set out to test whether JAK2 inhibition could abrogate CMML development in Cbl;Cbl-b conditional double-knockout mice.…”