Abstract 1627: Requirement for the Src family kinase, Fyn, in proliferation of BCR-ABL1 transduced bone marrow and aneuploidy in CML

Abstract Oncogenic signals stemming from the BCR/ABL kinase drive the development and progression of chronic myeloid leukemia (CML). Hence, therapies blocking kinase activity have proven extremely successful at managing this hematological malignancy. However, treatment of the terminal and progressed state of CML, blast crisis, remains difficult. Previous work from our group has identified the Src family kinase, Fyn, as being upregulated in blast crisis CML. We also reported that knockdown of Fyn slowed CML growth in vitro and in vivo and sensitized cells to BCR-ABL1 kinase inhibition with imatinib. Recent work using microarray profiling of kinase inhibitor resistant cells from a separate group has shown that imatinib resistance is associated with Fyn expression. In the current study, we utilized bone marrow cells from Fyn deficient mice to test the requirement for Fyn in p210 BCR-ABL1 mediated survival. Bone marrow cells from Fyn knockout and Fyn wildtype mice were harvested and transduced with a GFP expressing retroviral construct (MigR1) or MigR1-p210 BCR-ABL1. Cells were sorted for GFP expression and BCR-ABL1 expression was confirmed by Western blotting. Cell growth in culture was monitored over the course of three weeks in Fyn deficient and wildtype cells expressing BCR-ABL1. Fourteen days post sorting, the number of cells lacking Fyn were more than 50% lower than Fyn wildtype cells transduced with BCR-ABL1. Clonogenic assays further indicated that Fyn significantly promotes BCR-ABL1 induced bone marrow cell growth. Colony numbers in Fyn deficient cells expressing BCR-ABL1 were less than half that seen in Fyn wildtype cells. To address the role for Fyn kinase activity in these effects, constitutively active and dominant negative Fyn constructs have been transduced into BCR-ABL1 expressing cells. Constitutively active Fyn caused a high degree of chromosomal aberrations, fusions and aneuploidy suggestive of genomic instability. Taken together, these data highlight a significant role for Fyn in BCR-ABL1 mediated proliferation and secondary chromosomal aberrations, which are both features characteristic of blast crisis CML. Our results indicate that strategies to inhibit Fyn expression and kinase activity will be therapeutically relevant for progressed and/or refractory CML patients. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1627.