A Prevalent Cancer Associated Glycan, Globo H Ceramide, Induces Immunosuppression by Reducing Notch1 Signaling

Globo H, a hexasaccharide initially identified as a ceramide-linked glycolipid from human breast cancer cell line MCF-7, is over-expressed on the surface of many common cancers, but its function is unknown.Here we demonstrated the uptake of globo H ceramide (GHCer) by human peripheral blood mononuclear cells (PBMC) upon co-culture with MCF-7 cells.Significantly, the expression of globo H on tumor-infiltrating lymphocytes was observed in 61% of globo H positive breast cancer tissues.Addition of synthetic GHCer to human PBMC, mouse splenocytes or purified CD4+ T cells inhibited their proliferative response to anti-CD3/CD28 to 60 ± 1%, 50 ± 7% and 62 ± 5% of control, respectively, and reduced the secretion of IL-2, IFN-γ and IL-4.GHCer also significantly suppressed the proliferation of splenocytes or purified CD19+ B cells to 45 ± 10% and 26 ± 3% of control in response to LPS or LPS + IL4 +CD40 ligand and their IgM production to 12 ± 5%, 8 ± 3%, and IgG to 34 ± 9%, 35 ± 5%, respectively, with neglible induction of plasma cells.Ceramide displayed no such inhibitory effects.On the other hand, GHCer failed to raise the number of regulatory T cells, or their expression of FOXP3/CTLA4, nor did it increase apoptosis.Notably, GHCer significantly suppressed the Notch1 signaling during activation of human PBMC and murine T and B cells.Furthermore, GHCer upregulated the expression of id3 and itch by 2.1±0.2 and 4.7 ± 0.4 folds, respectively, leading to ID3-dependent downregulation of Notch1 and Itch-mediated Notch1 degradation.These results provide the first evidence for GHCer to facilitate the escape of cancer cells from immune surveillance.