Mainly restricted to the nervous system in healthy adults, complex
gangliosides such as GD3 and GD2 have been shown to be involved in aggressiveness and
metastasis of neuro-ectoderm derived
tumors such as
melanoma and
neuroblastoma. Interestingly, O-acetylated forms of GD2, not expressed in human peripheral nerve fibers, are highly expressed in GD2+
tumor cells. Very little information is known regarding the expression of O-acetylated
disialogangliosides in
breast cancer (BC) cell lines. Here, we analyzed the expression of GD2, GD3 and their O-acetylated forms O-acetyl-GD2 (OAcGD2) and O-acetyl-GD3 (OAcGD3) in BC cells. We used Hs 578T and SUM159PT cell lines, as well as cell clones over-expressing GD3 synthase derived from MDA-MB-231 and MCF-7. Using flow cytometry and immunocytochemistry/confocal microscopy, we report that BC cells express b-series
gangliosides GD3 and GD2, as well as significant amounts of OAcGD2. However, OAcGD3 expression was not detected in these cells. O-acetylation of
gangliosides isolated from BC cells was examined by LC-MS analysis of
sialic acid DMB-derivatives. We report that the main acetylated form of
sialic acid expressed in BC
gangliosides is
9-O-acetyl-N-acetylneuraminic acid (Neu5,9Ac2). These results highlight a close interrelationship between Neu5,9Ac2 and OAcGD2 expression, and suggest that OAcGD2 is synthetized from GD2 and not from OAcGD3 in BC cells.