CHARACTERIZATION OF LYMPHOBLAST PEPTIDE RECEPTORS

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In the past, we developed an assay which supports the growth of malignant colonies from children with acute lymphoblastic leukemia and non-Hodgkin's lymphoma. Our methodology differs from in vitro culture techniques reported by others in that (albeit sporadically) long term cell growth and cell line establishment from passage of a single colony could be accomplished. Cell line establishment, however, is important because cell lines provide an unlimited, stable source of cells for in vitro studies. Cell lines established in our laboratory have been shown to have the same immunophenotype, biochemical enzyme profile, immunogenotype and karyotype as the patient's tumor. We have recently determined that different subtypes of malignant lymphoblasts possess unique profiles for receptors to peptide hormones. While each of 9 immature T-lymphoblast cell lines possess IGF-I receptors and lack insulin receptors, 19 of 20 immature B-lymphoblast cell lines possess insulin receptors and lack IGF-I receptors. We have shown that T-lymphoblasts proliferate in response to nanogram concentrations of IGF-I but not insulin in serum-free media. Moreover, supplemental IGF-I has proven to be a key growth factor necessary in the development of a reproducible, standardized method for the establishment of T-lymphoblast cell lines in vitro. Based on these data, we hypothesize that peptide hormones such as insulin and IGF-I may be critical growth factors necessary for the proliferation of malignant hematopoietic cells and that peptide receptor function blockage may severely limit cellular proliferation. The objective of this proposal is to study the biologic function of specific peptides (I, IGF-I, IGF-II, CH) on malignant hematopoietic cells which possess (or lack) specific peptide receptors, and to determine the specificity, kinetics, structure and function on specific peptide receptors by binding studies, chemical cross-linking on SDS-PAGE, receptor phosphorylation and by polyclonal and monoclonal antireceptor antibodies. These studies will augment our understanding of peptide/peptide receptor function in malignant cells, will help establish standard methodologies for cell line establishment, and may provide the foundation for antipeptide receptor therapy for hematopoietic malignancies in the future.