cdw17-antigen and Melanoma

Tumor escape is linked to multiple mechanisms, notably the liberation, by tumor cells, of soluble factors that inhibit the function of dendritic cells (DC). We have shown that melanoma gangliosides impair DC differentiation and induce their apoptosis. The present study was aimed to give insight into the mechanisms involved. DC apoptosis was independent of the catabolism of gangliosides since lactosylceramide did not induce cell death. Apoptosis induced by GM3 and GD3 gangliosides was not blocked by inhibitors of de novo ceramide biosynthesis, whereas the acid sphingomyelinase inhibitor desipramine only prevented apoptosis induced by GM3. Furthermore, our results suggest that DC apoptosis was triggered via caspase activation, and it was ROS dependent with GD3 ganglioside, suggesting that GM3 and GD3 induced apoptosis through different mechanisms.

Topics: Antigens, CD; Apoptosis; Caspase Inhibitors; Caspases; Ceramides; Cysteine Proteinase Inhibitors; Dendritic Cells; Enzyme Activation; G(M3) Ganglioside; Gangliosides; Humans; Lactosylceramides; Melanoma; Monocytes; Oligopeptides; Tumor Escape

The glycosphingolipid patterns were analyzed on two clones derived from a human melanoma cell line and selected for their respectively high and low metastatic ability in immunosuppressed newborn rats. Conversely to the weakly metastatic cells which exhibited a pattern similar to that of the parental cell line, highly metastatic human melanoma cells appeared to be deficient in ganglioside biosynthesis. An accumulation of lactosylceramide was found in the latter cells, with low amounts of GM3 as the only ganglioside detected and a fourfold decreased activity of GM3 synthase (EC 2.4.99.9). After subcutaneous injection of metastatic cells in newborn rats, the cells proliferating in the tumor induced at the injection site re-expressed the four common gangliosides of melanoma: GM3, GM2, GD3 and GD2, whereas the cells growing in the lungs as metastatic nodules were deficient in ganglioside synthesis and showed an accumulation of lactosylceramide. Taken together, our results suggest that the human melanoma cells which are able to escape from the primary tumor and invade the lungs have an impaired ganglioside biosynthesis with a deficient GM3 synthase.

Topics: Animals; Animals, Newborn; Antigens, CD; G(M2) Ganglioside; G(M3) Ganglioside; Gangliosides; Glycosphingolipids; Humans; Lactosylceramides; Melanoma; Neoplasm Metastasis; Neoplasm Transplantation; Rats; Sialyltransferases; Tumor Cells, Cultured

Surface galactosyltransferase (GT) has been described on a variety of cells where it is believed to be involved in cell-cell and cell-substratum adhesion. Here we show that B16 metastatic murine melanoma cells exhibit a 5-fold higher cell surface GT activity than their nonmetastatic counterparts, although total GT activity in NP-40 solubilized cells is similar for both melanoma variants. Interestingly, on living cells, this cell surface GT almost exclusively galactosylates an endogenous glycoprotein (Mr = 110,000). This metastasis-associated GT is specific for terminal D-N-acetylglucosamine, catalyzes the formation of a beta 1-4 linkage, does not recognize polylactosaminoglycans, and has its specificity altered from D-N-acetylglucosamine to D-glucose by alpha-lactalbumin; yet the Mr = 110,000 protein is not a major substrate when exogenous bovine GT is used on the outside of living cells. In addition to this protein-specific endogenous GT activity, another cell surface GT activity that selectively galactosylates glucosylceramide is also prominent. Endogenous galactosylation of both protein and glycolipid substrates is reduced when the membrane is solubilized by the detergent NP-40 but remains unaltered in the presence of digitonin, which permeabilizes but does not dissolve the membrane. These data suggest that the GTs and their substrates are associated on the cell surface. Chloroquine treatment of intact cells leads to a 4-fold and a 3-fold increase in galactosylation of the Mr = 110,000 protein and glucosylceramide, respectively, suggesting that these two substrates normally reside mostly in the lysosomal or Golgi compartments. The increased expression of lysosomal membrane proteins on the surfaces of highly metastatic cells may, in part, also explain the galactosylation differences observed. These studies further suggest that increased surface localization of certain glycosyltransferases with highly restricted in situ substrate specificities may be a common feature of highly metastatic tumor cells.

Topics: Animals; Antigens, CD; Cell Membrane; Chloroquine; Chromatography, Thin Layer; G(M1) Ganglioside; Galactose; Galactosyltransferases; Glycolipids; Glycoproteins; Glycosphingolipids; Glycosylation; Isomerism; Lactalbumin; Lactosylceramides; Melanoma; Mice; Molecular Weight; Neoplasm Metastasis; Protein Processing, Post-Translational; Tumor Cells, Cultured