Synthesis and evaluation of Nα,Nε-diacetyl-L-lysine-inositol conjugates as cancer-selective probes for metabolic engineering of GPIs and GPI-anchored proteins

Two myo-inositol derivatives having a removable Nα,Ne-diacetyl-L-lysine (Ac2Lys) moiety linked to the inositol 1-O-position through a self-cleavable linker and a metabolically stable 2-azidoethyl group linked to the inositol 3-O- and 4-O-positions, respectively, were designed and synthesized. The Ac2Lys moiety blocking the inositol 1-O-position required for GPI biosynthesis was expected to be removable only by a combination of two enzymes, histone deacetylase (HDAC) and cathepsin L (CTSL), abundantly expressed in cancer cells, but not in normal cells, to convert the inositol derivatives into products with a free 1-O-position that were biosynthetically useful. As a result, it was found that these inositol derivatives could be incorporated by cancer cells, but not by normal cells, to express azide-labeled glycosylphosphatidylinositols (GPIs) and GPI-anchored proteins on the cell surface. Consequently, this research has established a novel strategy and new molecular tools for selective metabolic labeling of cancer cells, which should be useful for various biological studies and applications.