Enhanced Antitumor Effects by Chemical Modified IGb3 Analogues

Abstract

Certain glycolipid antigens for natural killer T (NKT) cells can direct the overall cytokine balance of the immune response. However, the molecular mechanism of Th1-or Th2-biased cytokine secretion by NKT cells is still unknown. Previously, we synthesized isoglobotrihexosylceramide (iGb3) analogues by introducing a hydroxyl group at C4 on the ceramide portion of iGb3 to produce 4-HO-iGb3 or to further deoxylation on the terminal galactose to produce 4 000 -dh-iGb3. Both modified iGb3, especially 4 000 -dh-iGb3, stimulated more IFN-g production by hepatic NKT cells, and thus elicited preferential Th1 responses. Here, we found that 4 000 -dh-iGb3-loaded bone marrow-derived dendritic cells (DC) could significantly inhibit growth of subcutaneous melanoma and suppress lung metastasis in C57BL/6 mice compared with unmodified iGb3-loaded DCs. In investigating the mechanisms of this improved activity, we found that 4 000 -dh-iGb3 stimulation increased STAT1 signaling by NKT cells, whereas the phosphorylation of Th2 type cytokine-associated transcription factor STAT6 signaling was not affected. Analysis of the structures of iGb3 and 4 000 -dh-iGb3 revealed that 4 000 -dh-iGb3 provides greater stability and affinity between glycolipid and CD1d or NKT TCR complex than iGb3. Thus, 4 000 -dh-iGb3 can improve the antitumor effects of a DC-

Lack of iGb3 and Isoglobo-Series Glycosphingolipids in Pig Organs Used for Xenotransplantation: Implications for Natural Killer T-Cell Biology

“…[13-16] Invariant NKT cells are innate immune cells functionally similar to NK cells. The semi-invariant NKT-cell receptor recognizes glycolipid antigens presented by the monomorphic CD1d molecule.…”

Novel lipid antigens for NKT cells in cancer

“…With respect to cancer therapy, GSLs have shown potential utility. Chemical derivatives of iGb3 have been found to stimulate NKT cells in a CD1d-dependent manner and even skew the NKT cell response towards a more anti-tumor Th1 response dominated by IFN-γ secretion ( 98 ). In addition, the ganglioside NGcGM3 is not expressed in normal human tissues due to a genetic mutation in an enzyme involved in its synthesis.…”

The NKT cell TCR repertoire can accommodate structural modifications to the lipid and orientation of the terminal carbohydrate of iGb3

“…Such insight would be useful for understanding the key structural requirements of CD1d ligand binding and NKT cell activation, which in turn will allow for a better understanding of how iGb3 analogues might be used in a therapeutic setting. 25 …”

“…Such insight would be useful for understanding the key structural requirements of CD1d ligand binding and NKT cell activation, which in turn will allow for a better understanding of how iGb3 analogues might be used in a therapeutic setting. 25 To prepare bG-iGb3 (3), we envisioned using lactosyl 2-azidosphingosine intermediate 8, previously identied as a versatile intermediate for the preparation of iGb3 analogues. 20 Accordingly, we proposed that the synthesis of bG-iGb3 (3, Scheme 1) would be carried out via the installation of the C26 amide aer the reduction of the azide on intermediate 8 and coupling with hexacosanoic acid (9) followed by selective acetylation via orthoester opening 26 to give the 4 00 -O-acetyl derivative, and subsequent glycosylation with imidate donor 10 containing a bdirecting C-2 participating group.…”