COMPLEMENTARY SELECTION-BASED APPROACHES FOR THE DISCOVERY OF GALECTIN INHIBITORS - PROJECT SUMMARY GALECTINS ARE CARBOHYDRATE BINDING PROTEINS (CBPS) THAT RECOGNIZE AND BIND TO B-GALACTOSIDE SUGARS ON THEIR VARIOUS BINDING PARTNERS. THE GALECTIN FAMILY OF PROTEINS ARE KEY REGULATORS OF THE IMMUNE SYSTEM, AND THE DIVERSE ROLES OF GALECTINS IN DISEASE STATES MAKE THEM ATTRACTIVE TARGETS FOR DRUG DISCOVERY. SPECIFICALLY, GALECTIN-1 HAS BEEN SHOWN TO INDUCE CELL DEATH IN IMMUNE CELLS THROUGH INTERACTIONS WITH SUGARS ON THE CELL SURFACE. GALECTIN-1 IS OVEREXPRESSED IN VARIOUS VIRAL INFECTIONS AND MANY TUMOR TYPES, AND ITS ANTI-INFLAMMATORY ACTIVITY IS BELIEVED TO PLAY A ROLE IN VIRUS AND TUMOR IMMUNE ESCAPE. THE EXACT MECHANISMS OF IMMUNE MODULATION BY GALECTIN-1 REMAIN POORLY UNDERSTOOD. THUS, GALECTIN-1 INHIBITORS HAVE APPLICATIONS AS BOTH POTENTIAL THERAPEUTICS AS WELL AS POWERFUL TOOLS FOR BASIC SCIENCE. THE DEVELOPMENT OF SMALL MOLECULE GALECTIN-1 INHIBITORS IS CHALLENGING FOR SEVERAL REASONS. GALECTIN-1 BINDS WEAKLY TO FREE SUGARS, HOWEVER IT BINDS VERY TIGHTLY TO ITS NATURAL GLYCOSYLATED LIGANDS. TIGHT BINDING IS ACHIEVED THROUGH THE SPECIFIC SPATIAL PRESENTATION OF SUGARS ON THE LIGAND, THE NUMBER OF SUGARS ON THE LIGAND, AND ADDITIONAL FUNCTIONAL GROUPS ON THE LIGAND. ADDITIONALLY, ACHIEVING SPECIFIC INHIBITION OF A SINGLE GALECTIN FAMILY MEMBER IS DIFFICULT DUE TO HIGH LEVELS OF SEQUENCE SIMILARITY AMONG GALECTINS. THIS PROPOSAL AIMS TO APPLY THE SELMA (SELECTION WITH MODIFIED APTAMERS) METHOD OF DIRECTED EVOLUTION TO DEVELOP POTENT, SPECIFIC INHIBITORS OF GALECTIN-1. THIS METHOD IS UNIQUELY SUITED TO THE CHALLENGE OF DEVELOPING GALECTIN INHIBITORS AND WILL PRODUCE RNA SUPPORTED GLYCO-CLUSTERS AND GLYCOSYLATED RNA APTAMERS TARGETED TO THE GALECTIN-1 CARBOHYDRATE RECOGNITION DOMAIN. SELMA TAKES ADVANTAGE OF HIGH LEVELS OF SEQUENCE AND STRUCTURAL DIVERSITY ENCODED BY NUCLEIC ACID LIBRARIES AS WELL AS SUGAR-TARGET INTERACTIONS TO MIMIC NATURAL LIGANDS OF GALECTIN-1. THESE INHIBITORS CAN SERVE AS BOTH PRELIMINARY DRUG CANDIDATES FOR ANTI-VIRAL AND ANTI-CANCER THERAPEUTICS, AND TOOLS TO DECONVOLUTE THE ROLE OF GALECTIN-1. MOREOVER, THESE METHODS CAN BE EXTRAPOLATED TO TARGET ADDITIONAL MEMBERS OF THE GALECTIN FAMILY, AS WELL AS SIMILARLY DIFFICULT CBPS.