Functions of
glycosphingolipids on the eukaryotic cell membranes during the onset of oncogenic processes and cell death are not well understood. Inhibitors of
glycosphingolipid biosynthesis were recently found to trigger apoptosis in many
carcinoma including
breast cancer SKBR-3, MCF-7, and MDA-468 cells through either intrinsic or extrinsic apoptotic pathways as we previously reported. These anti-
cancer inhibitors could increase
ceramide concentration by blocking functions of
glycolipid glycosyltransferases (GLTs). In this study, using a novel
fluorescent dye (ASK-0) revealed the damage of cell organelle membranes by an inhibitor of
glucosylceramide biosynthesis (L-
PPMP). A highly
drug- and cell-dependent regulation of MAPKs was also found by cis-platin and L-
PPMP when inducing apoptosis in SKBR-3, MCF-7, and MDA-468 cells. A dose and time-dependent regulation of GLTs were investigated by enzymatic assay and
DNA microarray analyses. These GLTs are involved in biosynthesis of Le(X) and sialosyl-Le(X) (neolactosyl-
ceramide series) such as
GalT-4 (
UDP-Gal: LcOse3cer beta-
galactosyltransferase, GalT-5 (
UDP-Gal: nLcOse4Cer alpha1, 3galactosyltransferase, FucT-3 (
GDP-Fucose: LM1 alpha1, 4fucosyltransferase). A similar effect was observed with the GLTs involved in the biosyntheses of Gg-series
gangliosides, such as SAT-4 (
CMP-NeuAc: GgOse4Cer alpha2, 3sialyltransferase, and SAT-
2 (CMP-NeuAc: GM3 alpha2, 8sialyltransferase). The glycol-related gene
DNA-microarrays also suggested the transcriptional regulation of several GLTs involved in the biosynthesis of neolactosylceramide containing
cell-surface antigens in these apoptotic
breast carcinoma cells. In the early apoptotic stages (2 to 6 h after L-
PPMP treatment) in addition to GlcT-1 gene, several genes (betaGalTs and betaGlcNAcTs) in the SA-Le(a) pathway were stimulated.