TYROSINE KINASE FUSION IN HEMATOLOGIC MALIGNANCY

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This project will characterize the role of tyrosine kinase fusions in pathogenesis of hematologic malignancy, through development of murine models of leukemia and lymphoma. Our laboratory has recently cloned several tyrosine kinase fusions which will provide the basis for these studies. We have cloned the TEL-PDGFRbeta fusion and related variants associated with t(5;12) chronic myelomonocytic leukemia (CMML), and a novel TEL-ABL fusion associated with acute myeloid leukemia. Our collaborator, has cloned athe NPM-ALK tyrosine kinase fusion associated with high grade lymphomas. We will develop murine models of leukemia and lymphoma using the TEL-PDGFRbeta, TEL-ABL and NPM-ALK fusions. As with BCR-ABL in chronic myelogenous leukemia (CML), TEL-PDGFRbeta, TEL- ABL and NPM-ALK may confer a malignant phenotype by constitutive activation of the tyrosine kinase domains of PDGFRbeta and ALK. In Specific Aim 1 we will characterize involvement of TEL and PDGFRbeta in patients with (i) CMML and t(5;12) translocation, (ii) CMML with normal karyotype, (iii) other FAB subtypes of myelodysplastic syndrome, (iv) myeloid metaplasia and myelofibrosis, (v), acute monocytic leukemias, and (vi) hematologic malignancy with 12p13 cytogenetic abnormalities. These studies will help to clarify the role of TEL and PDGFRbeta in pathogenesis of hematologic malignancy, and may provide insight into functional domains which are important in transforming activity. In Specific Aim 2, transforming activity of the TEL-PDGFRbeta and TEL-ABL fusion gene will be confirmed in stably transfected mammalian cell lines. Expression of TEL-PDGFRbeta and TEL-ABL fusions will be confirmed by immunoblotting and in vitro kinase assays. Specific Aims 1 and 2 will provide the basis for Specific Aim 3 will assess transforming potential of the TEL-PDGFRbeta, TEL-ABL and NPM- ALK fusions in murine bone marrow transplant models of leukemia and lymphoma. Evaluation of transplanted mice will include detailed histopathologic examination; white blood cell differential and immunophenotype analysis to determine lineage involvement of hematological malignancy; and analysis of leukemic cells and leukemic cell lines from transplanted mice for evidence of proviral integration and expression of the fusion protein. These studies will characterize the role of the TEL- PDGFRbeta, TEL-ABL and NPM-ALK fusion proteins in pathogenesis of leukemia and lymphoma, and may provide insight into more effective therapy of hematologic malignancy mediated by tyrosine kinase fusions. Furthermore, these studies will provide a foundation for immunotherapeutic approaches to leukemia and lymphoma.