Profiling of O -acetylated Gangliosides Expressed in Neuroectoderm Derived Cells.

The expression and biological functions of oncofetal markers GD2 and GD3 were extensively studied in neuroectoderm-derived cancers in order to characterize their potential as therapeutic targets. Using immunological approaches, we previously identified GD3, GD2, and O AcGD2 expression in breast cancer (BC) cell lines. However, antibodies specific for O -acetylated gangliosides are not exempt of limitations, as they only provide information on the expression of a limited set of O -acetylated ganglioside species. Consequently, the aim of the present study was to use structural approaches in order to apprehend ganglioside diversity in melanoma, neuroblastoma, and breast cancer cells, focusing on O -acetylated species that are usually lost under alkaline conditions and require specific analytical procedures. We used purification and extraction methods that preserve the O -acetyl modification for the analysis of native gangliosides by MALDI-TOF. We identified the expression of GM1, GM2, GM3, GD2, GD3, GT2, and GT3 in SK-Mel28 (melanoma), LAN-1 (neuroblastoma), Hs 578T, SUM 159PT, MDA-MB-231, MCF-7 (BC), and BC cell lines over-expressing GD3 synthase. Among O -acetylated gangliosides, we characterized the expression of O AcGM1, O AcGD3, O AcGD2, O AcGT2, and O AcGT3. Furthermore, the experimental procedure allowed us to clearly identify the position of the sialic acid residue that carries the O -acetyl group on b- and c-series gangliosides by MS/MS fragmentation. These results show that ganglioside O -acetylation occurs on both inner and terminal sialic acid residue in a cell type-dependent manner, suggesting different O -acetylation pathways for gangliosides. They also highlight the limitation of immuno-detection for the complete identification of O -acetylated ganglioside profiles in cancer cells.