Modeling chronic myeloid leukemia in immunodeficient mice reveals expansion of aberrant mast cells and accumulation of pre-B cells

Abstract

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm that, if not treated, will progress into blast crisis (BC) of either myeloid or B lymphoid phenotype. The BCR-ABL1 fusion gene, encoding a constitutively active tyrosine kinase, is thought to be sufficient to cause chronic phase (CP) CML, whereas additional genetic lesions are needed for progression into CML BC. To generate a humanized CML model, we retrovirally expressed BCR-ABL1 in the cord blood CD34+ cells and transplanted these into NOD-SCID (non-obese diabetic/severe-combined immunodeficient) interleukin-2-receptor γ-deficient mice. In primary mice, BCR-ABL1 expression induced an inflammatory-like state in the bone marrow and spleen, and mast cells were the only myeloid lineage specifically expanded by BCR-ABL1. Upon secondary transplantation, the pronounced inflammatory phenotype was lost and mainly human mast cells and macrophages were found in the bone marrow. Moreover, a striking block at the pre-B-cell stage was observed in primary mice, resulting in an accumulation of pre-B cells. A similar block in B-cell differentiation could be confirmed in primary cells from CML patients. Hence, this humanized mouse model of CML reveals previously unexplored features of CP CML and should be useful for further studies to understand the disease pathogenesis of CML.

Transgenic expression of human cytokines in immunodeficient mice does not facilitate myeloid expansion of BCR-ABL1 transduced human cord blood cells

“…Isolation and transduction of cord blood CD34 + cells was done as previously described and was approved by the Lund/Malmö Ethical Committee and performed after informed consent in accordance with the Declaration of Helsinki [3, 7]. All animal experiments were approved by The Swedish Board of Agriculture, Malmö/Lund animal ethics committee in Lund, Sweden.…”

“…Long bones and spleens were collected for histopathology analysis as previously described [3]. Bone and spleen sections were stained using CD68 (Dako, Glostrup, Denmark).…”

“…Cells were prepared for flow cytometry as previously described [3] and the following antibodies were used: CD45-APC, CD15-BV605, CD33-PECy7 and Glycophorin A-PE (BD Biosciences, San Jose, CA, USA), CD33-BV421, CD19-PerCPCy5.5, CD14-BV605, CD117-PerCPCy5.5, CD3-PECy7 and FceRI-PE (BioLegend, San Diego, CA, USA).…”

“…Myeloid cell expansion is the key feature in human CML but in humanized mice, this expansion of human BCR-ABL1 expressing myeloid cells has been difficult to achieve. Other aspects of human CML, like the arrest of B cell development at the pre-B cell stage, have been successfully modeled [3]. Various strains of immunodeficient mice have been tested (non-obese diabetic/severe combined immunodeficient (NOD/SCID), NOD/SCID-β 2 M or NOD/SCID IL2–receptor gamma deficient (NSG) mice) to increase the level of myeloid engraftment, but with limited success.…”

The SCLtTAxBCR-ABL transgenic mouse model closely reflects the differential effects of dasatinib on normal and malignant hematopoiesis in chronic phase-CML patients

“…Lower doses may efficiently inhibit B cell development through inhibition of B cell receptor signaling but may not be sufficient to induce apoptosis [26]. B cell depletion in our BCR-ABL expressing mice was reversed by dasatinib, which is in keeping with a BCR-ABL mediated block in B cell differentiation [27] as well as induction of apoptosis of BCR-ABL positive lymphoid cells [28]. …”