FUNCTION AND STRUCTURE OF NOVEL HUMAN BONE MARROW CAMS

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The lone-term objective of this proposal is to investigate the role of novel bone marrow stromal cell adhesion molecules (BM CAMs) in normal and leukemic hematopoiesis. Development of a 2-D cell blotting technique led to identification of about 22 potentially novel BM CAMs that show hematopoietic cell adhesion, with the more immature cells binding to a greater variety of CAMs. Of these, BM CAM 2 supports adhesion of monocytic progenitors, including KG1a cells induced with TNFa, whereas, BM CAM 6 binds to TNFa-induced KG1a cells only after they have been further stimulated by cross-linking of CD34 or CD49d using anti-CD34 or anti-CD49d MoAbs. The specific aims are to: 1) Confirm adhesive function and stromal expression of BM CAMs 2 and 6. 2) Establish the identity of BM CAMs 2 and 6 by determining their cDNA sequences. 3) Test the hypothesis that binding of early progenitors with monocytic differentiation potential to BM CAM 2 and/or BM CAM 6 promotes monocytic development, predicated on the basis that BM CAMs 2 and 6 function as molecular regulatory components of an interactive network of adhesive proteins and their receptors. The research design and the methods to be used are purification of BM CAMs 2 and 6 by an adaptation(s) to preparative-level 2-D gel electrophoretic techniques; generation of their respective antibodies by standard methods; cDNA cloning and sequencing by established procedures; and testing the role of BM CAMs 2 and 6 in monocytopoiesis using the recombinant BM CAMs. The endpoint for entry into the definitive monocyte lineage will be assessment of expression of the M-CSF receptor (coded for by c-fms proto- oncogene), which renders the progenitor cells responsive to M-CSF and subsequently to other appropriate cytokines leading to the development of mature monocytes/ macrophages. The prediction that the engagement of progenitor cell receptors, by binding to BM CAMs 2 and 6, results in down- regulation of the known PC CAMs will be verified, providing a possible mechanism for the release of matured cells from the BM. The health- relatedness of the project is that it provides an understanding of basic mechanisms related to the growth and development of normal and leukemic blood cells. The antibodies generated during this project would be potentially useful for treating and preventing the spread of leukemias and lymphomas by dislodging the neoplastic cells from their metastatic sites; and for mobilizing normal progenitors into the peripheral blood for harvesting and use in transplantation.