ABSTRACT
Philadelphia chromosome-positive leukemias, including chronic myeloid leukemia and B-cell acute lymphoblastic leukemia (B-ALL), are driven by the oncogenic BCR-ABL fusion protein. Animal modeling experiments utilizing retroviral transduction and subsequent bone marrow transplantation have demonstrated that BCR-ABL generates both myeloid and lymphoid disease in mice receiving whole bone marrow transduced with BCR-ABL. Y177 of BCR-ABL is critical to the development of myeloid disease, and phosphorylation of Y177 has been shown to induce GRB2 binding to BCR-ABL, followed by activation of the Ras and phosphoinositide 3 kinase signaling pathways. We show that the GRB2-related adapter protein, GADS, also associates with BCR-ABL, specifically through Y177 and demonstrate that BCR-ABL-driven lymphoid disease requires Gads. BCR-ABL transduction of Gads(-/-) bone marrow results in short latency myeloid disease within 3-4 weeks of transplant, while wild-type mice succumb to both a longer latency lymphoid and myeloid diseases. We report that GADS mediates a unique BCR-ABL complex with SLP-76 in BCR-ABL-positive cell lines and B-ALL patient samples. These data suggest that GADS mediates lymphoid disease downstream of BCR-ABL through the recruitment of specific signaling intermediates.
Subject(s)
Adaptor Proteins, Signal Transducing/metabolism , Fusion Proteins, bcr-abl/metabolism , Leukemia, Lymphoid/metabolism , Adaptor Proteins, Signal Transducing/genetics , Animals , Antigens, CD/metabolism , Blood Cells/metabolism , Bone Marrow/metabolism , Bone Marrow Transplantation , CD48 Antigen , Cell Line , Disease Models, Animal , Fusion Proteins, bcr-abl/genetics , Gene Expression , Hematopoiesis, Extramedullary , Humans , Immunophenotyping , Leukemia, B-Cell/genetics , Leukemia, B-Cell/metabolism , Leukemia, Lymphoid/genetics , Lymphoid Progenitor Cells/metabolism , Mice , Mice, Knockout , Multiprotein Complexes/metabolism , Phosphoproteins/metabolism , Protein Binding , Receptors, Cell Surface/metabolism , Signaling Lymphocytic Activation Molecule Family Member 1ABSTRACT
BCR-ABL induces chronic myeloid leukemia (CML) through the aberrant regulation of multiple signaling substrates. Previous research has shown that BCR-ABL mediates down-modulation of CBL-B protein levels. A murine bone marrow transplantation (BMT) study was performed to assess the contribution of Cbl-b to BCR-ABL-induced disease. The predominant phenotype in the Cbl-b(-/-) recipients was a CML-like myeloproliferative disease (MPD) similar to that observed in the wild-type animals, but with a longer latency, diminished circulating leukocyte numbers and reduced spleen weights. Despite the decreased leukemic burden in comparison to their wild-type counterparts, the Cbl-b(-/-) animals displayed enhanced numbers of Gr-1(+)/Mac-1(+) spleen cells and neutrophilia. On the basis of prior evidence of CBL-B-dependent motility toward SDF-1α, we hypothesized that Cbl-b deficiency might impair bone marrow localization during transplantation. Homing experiments showed reduced migration of Cbl-b(-/-) cells to the bone marrow. Intrafemoral transplantation of BCR-ABL-transduced Cbl-b(-/-) cells revealed equivalent latency of disease development to the wild-type transplants, supporting the conclusion that Cbl-b deficiency diminishes homing of leukemic cells to the bone marrow, and perturbs the proliferation of BCR-ABL-expressing malignant clones during CML development.
