Monosialoganglioside biosynthesis by subcellular membranes of rhabdomyosarcoma cell lines differing in metastatic potential.
We found that rhabdomyosarcoma (RMS) subcellular membranes contain sialyltransferase activities for LcOse4Cer and GgOse4Cer acceptors. Chromatographic analyses and neuraminidase lability of the sialyltransferase products indicated that the principal site of sialylation was the non-reducing terminal galactosyl moiety. In order to control for the effects of cell density in culture, metastatic S4T18 RMS cells and nonmetastatic F9-4/21 RMS cells were harvested at 2 X 10(4) to 6 X 10(4) per cm2 prior to analyses. Irrespective of metastatic potential, we found that sialyltransferase-specific activities were influenced by cell densities. F9-4/21 cells, for example, at a density of 6 X 10(4), produced membranes with sialyltransferase-specific activities to LcOse4Cer 1.9-fold higher than cells at 2.1 X 10(4)/cm2. Metastatic potential (predetermined in vivo) appeared to be correlated with an accelerated effect of cell density on the sialyltransferase activity to LcOse4Cer. Metastatic S4T18 cells at 6.3 X 10(4)/cm2 yielded membranes with sialyltransferase-specific activities 5.4-fold higher than membranes from cells at 1.9 X 10(4)/cm2. Conversely, fucosyltransferase activities in the presence of LcOse4Cer were highest in non-metastatic F9-4/21 cells at low cell densities. Quantitative analyses of monosialoganglioside fractions of RMS cells were in agreement with the sialyl-transferase studies. HPLC and HPTLC analyses demonstrated the presence of glucosamine-containing monosialoganglioside with Rf identical with the radioactive products of LcOse4Cer sialylation, which increased 4.5-fold on a per mg protein basis as cell densities increased in S4T18 cells in culture from 1.9 X 10(4)/cm2 to 6.3 X 10(4)/cm2. Plasma membrane marker Na+, K+, ATPase-specific activity also increased in RMS metastatic cells in a manner comparable to that described for the sialyl-transferase activity to LcOse4Cer. Our results suggest that metastatic potential is expressed in the rate of sialylation at specific membrane sites of RMS intercellular contact. We propose a process of selection for metastasis whereby specific cell surface non-reducing galactosyl termini are recognized by intercellular transferases and lectins in the primary tumor, and the corresponding labile sialylated sites (on disseminated cells) are recognized by host neuraminidases.
Liepkans
V A
VA
Laboratoire d'Immunochimie (UPR 277), I.R.S.C., Villejuif, France.
D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002250:Carbon Radioisotopes; D002460:Cell Line; D005732:Gangliosides / Q000096:biosynthesis*; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism*; D008563:Membrane Lipids / Q000096:biosynthesis*; D008969:Molecular Sequence Data; D019158:N-Acetylneuraminic Acid; D009362:Neoplasm Metastasis; D012208:Rhabdomyosarcoma / Q000378:metabolism* / Q000473:pathology; D012794:Sialic Acids / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000378:metabolism*
D002250:Carbon Radioisotopes; D005732:Gangliosides; D008563:Membrane Lipids; D012794:Sialic Acids; C025447:sialogangliosides; D019158:N-Acetylneuraminic Acid