Alterations of glycosphingolipids in embryonic stem cell differentiation and development of glycan-targeting cancer immunotherapy

All mammalian cells display an array of surface glycans that can modulate cellular interactions and regulate the development of an organism. In spite of their important implications in health and disease, investigations of glycans pose a great challenge given their inherent heterogeneity and the frequently observed cross-reactivities of antibodies against glycosphingolipids (GSLs) with multiple glycans, which may lead to erroneous interpretation and conclusion. We employed matrix-assisted laser desorption-ionization mass spectrometry and tandem MS/MS analyses to systematically delineate changes in GSLs during differentiation of human embryonic stem (ES) and induced pluripotent stem cells into various derivatives. In addition to the well-known human ES-specific markers, stage-specific embryonic antigen (SSEA)-3 and SSEA-4 and several globo- and lacto-series GSLs (Gb4Cer, Lc4Cer, fucosyl-Lc4Cer, Globo H, and disialyl-Gb5Cer) not reported previously were identified. A close association of the switching of core structures of GSLs from globo- and lacto- to ganglio-series during ES differentiation was revealed, consistent with the observed changes in GSL expression during murine embryonic development. Such switching was accompanied with the concerted changes in the expression of glycosyltransferases during differentiation. Finally, since aberrant glycosylation is a general feature of cancer, targeting tumor-associated surface glycans for cancer immunotherapy is gaining international attention. While GD2-targeted immunotherapy of neuroblastoma represents the first antiglycan monoclonal antibody to obtain FDA approval for standard medical care, Globo H-targeted immunotherapy of breast cancer has generated promising results in the ongoing multinational clinical trials. In this study, we also describe the studies of the scientific rationales for the use of glycans as anticancer immunotherapeutics.