Lectins are ubiquitous proteins which bind specifically and reversibly carbohydrates without modifying them. They can decipher the glycocode: information stored in carbohydrates found at the surface of any cell.  Lectins are involved in many biological processes such as cell cohesion, development, cell signaling, defense or microbial infections. They can present exploitable properties such as antiproliferative, antiviral or antitumor and are interesting tools in glycobiology. The fungal kingdom has attracted wide interest in the recent years since it is a promising and largely unexplored source for lectins for novel specificity and activities. Structural data are still limited for fungal lectins and this project aims to fill this gap of knowledge whilst studying new lectins specific for two glycosidic cancer markers. Via a multidisciplinary approach, we dissected the interaction of those lectins with their ligand at the atomic level or modified them to optimized their specificity or affinity. Recombinant wild-type and mutated lectins were expressed in Escherichia coli and then purified by classical chromatography methods. The specificity and affinity were determined by different techniques such as hemagglutination, glycan arrays, and microcalorimetry. Finally, structural characterization was performed by X?ray crystallography in order to localize the sugar binding site, to obtain the specific protein and ligand determinants necessary for the interaction and to help for the design and structural evaluation of mutants. Finally, analysis on cancer cells and tissues confirmed their potential as labelling tools thereafter for biomedical or biotechnological applications.