METASTATIC REGULATION OF DIFFERENTIAL SPLICING OF CD44

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THIS IS A SHANNON AWARD PROVIDING PARTIAL SUPPORT FOR THE RESEARCH PROJECTS THAT FALL SHORT OF THE ASSIGNED INSTITUTE'S FUNDING RANGE BUT ARE IN THE MARGIN OF EXCELLENCE. THE SHANNON AWARD IS INTENDED TO PROVIDE SUPPORT TO TEST THE FEASIBILITY OF THE APPROACH; DEVELOP FURTHER TESTS AND REFINE RESEARCH TECHNIQUES; PERFORM SECONDARY ANALYSIS OR AVAILABLE DATA SETS; OR CONDUCT DISCRETE PROJECTS THAT CAN DEMONSTRATE THE PI'S RESEARCH CAPABILITIES OR LEND ADDITIONAL WEIGHT TO AN ALREADY MERITORIOUS APPLICATION. THE ABSTRACT BELOW IS TAKEN FROM THE ORIGINAL DOCUMENT SUBMITTED BY THE PRINCIPAL INVESTIGATOR. DESCRIPTION (adapted from the investigator's abstract): During metastasis, tumor cells break away from the primary tumor mass and pass through the extracellular matrix to invade other areas of the body. The ability of tumor cells to penetrate the matrix and attach to each other is, in part, due to the presence of cell surface proteins on tumor cells that interact with either the extracellular matrix or with cell surface proteins on other cells. One such cell surface protein whose extracellular domains have been correlated with metastatic potential is the multifunctional adhesion glycoprotein, CD44, which is expressed in a wide variety of cells in mammals. RNA from the CD44 gene undergoes extensive alternative splicing. The gene contains 10 internal cassette exons that are alternatively included to produce variant forms of CD44 with additional extracellular domains that influence the binding specificity of cells bearing CD44. Inclusion of a specific sub-set of the alternative exons has a strong correlation with metastatic spread in colon, breast, ovarian and brain cancer such that expression of variant forms of CD44 is now used to assess metastatic potential of human cancers. Expression of CD44 cDNAs containing the alternatively-included exons associated with metastasis is sufficient to confer metastasis on syngenic tumor cells and antibodies to the variant form of CD44 prevent metastatic spread in animal models. Therefore, alteration in the splicing pattern of CD44 mRNA is sufficient to render a tumor cell metastatic. This proposal is aimed at understanding the molecular mechanism involved in the alternative splicing of CD44 during metastasis of ovarian and breast cancer tumor cell lines and comparing the metastatic alternative splicing to that occurring during growth stimulation of leukocyte or epithelial cells and during tissue formation in early development. Specific aims include: 1) determination of the cis-acting sequences that regulate inclusion of the CD44 alternative exons. The goal of these experiments is to distinguish regulation of splicing due to tissue- specific factors from regulation of splicing due to alterations in the levels or activities of the general splicing machinery; 2) determination of the trans-acting factors required for regulation of inclusion of the CD44 alternative exons in metastatic versus normal cells; 3) Investigation of the relationship between the alternative splicing event producing the CD44 metastatic variants and normal tissue establishment during early mammalian development.