Bendicht Pauli, College of Veterinary Medicine

Research in the Pauli laboratory is concerned with cellular and molecular aspects of cancer metastasis. A major priority has been to understand the contribution of endothelial cell adhesion molecules to site-specific metastasis. A lung-specific endothelial cell adhesion molecule (Lu-ECAM-1) has been isolated, purified, and cloned that promotes the selective adhesion of lung-metastatic melanoma cells in vitro and mediates experimental metastasis of the lungs by these tumor cells in vivo. Anti-Lu-ECAM-1 monoclonal antibodies inhibit colonization of the lungs by lung-metastatic melanoma cells, but have no effect on the colonization of the lungs by other types of lung-metastatic cancers. Genomic Southern blot analyses show that the Lu-ECAM-1 gene is present in all mammalian species tested, usually as a single copy, but is absent in chicken and yeast.

Current studies are directed toward

(a) isolating and cloning the Lu-ECAM-1 ligand of melanoma cells and identifying the binding domains of the interacting adhesion receptor/ligand pair using oligonucleotide-directed mutagenesis and carbohydrate analysis (mapping and composition of oligosaccharides);

(b) determining the Lu-ECAM-1 ligand expression levels during melanoma progression in order to explore whether the Lu-ECAM-1 ligand might be useful as a prognostic indicator in melanoma disease;

(c) identifying the cellular proteins that interact with the cytoplasmic domain of Lu-ECAM-1 in order to further define the function of this adhesion molecule, using glutathione-S-transferase/Lu-ECAM-1 fusion proteins and the yeast cell two hybrid system;

(d) generating sufficient amounts of the recombinant ligand-binding and cytoplasmic domains from E.coli for their structural determination; by either X-ray crystallography or NMR and

(e) generating Lu-ECAM-1 knockout mice to provide ultimate information on the functional roles of the Lu-ECAM-1 gene.

Collaborative work is also underway with the Oswald laboratory to understand the biological implications of the sequence similarities between Lu-ECAM-1 and chloride channels (Section B3b., below). Clinically, these studies build the foundation for the identification of novel prognostic indicators of melanoma disease (Lu-ECAM-1 ligand expression levels) and for the design of new therapeutic strategies directed against melanoma dissemination based on anti-adhesion (e.g., anti-Lu-ECAM-1 monoclonal or polyclonal antibodies; synthetic peptides [or carbohydrates] directed against the binding domains; Lu-ECAM-1 anti-sense oligonucleotides). Similar studies are being conducted to evaluate the role of a second endothelial cell adhesion molecule, dipeptidyl peptidase IV (DPP IV), in lung metastasis of breast cancer cells.