fumonisin-b1 and Melanoma

We evaluated the cytotoxic effects of a cell-permeable ceramide (Cer), N-hexanoyl-D-sphingosine (C6-Cer) and of two related sphingoid bases, sphingosine (So) and dihydrosphingosine (sphinganine; Sa) on human melanoma cell lines and on soft tissue sarcoma lines recently established from fresh surgical biopsy specimens. These cell lines ranged from high susceptibility (939 melanoma) to strong resistance (A2058 melanoma and all three sarcomas) to tumour necrosis factor (TNF), an inducer of elevated intracellular Cer levels. However, all the cell lines demonstrated a dose-dependent susceptibility to C6-Cer with protracted cytotoxic kinetics, with the C8161 melanoma being the most sensitive and A2058 the least. Protein kinase C (PKC) antagonizes Cer-dependent apoptosis, and chelerythrine chloride, So and Sa, which inhibit PKC, caused extremely rapid cytotoxicity of melanoma cell lines, irrespective of their relative sensitivity to C6-Cer. So-mediated cytotoxicity was extensive even after only 90 min of treatment, within the time frame of limb perfusion. So and Sa only slightly potentiated the cytotoxic responses to TNF, C6-Cer or melphalan. Sphingolipid-driven intracellular pathways may offer opportunities for therapy of these tumours.

Topics: Alkaloids; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Benzophenanthridines; Carboxylic Acids; Cell Survival; Ceramides; Dose-Response Relationship, Drug; Fumonisins; Histiocytoma, Benign Fibrous; Humans; Lung Neoplasms; Melanoma; Melphalan; Phenanthridines; Protein Kinase C; Sarcoma; Signal Transduction; Sphingosine; Time Factors; Tumor Cells, Cultured; Tumor Necrosis Factor-alpha

With an experimental model of spontaneous lung metastases of melanoma developed in this laboratory, a range of sublines (variants and clones) with different metastatic potential and ganglioside expression was established from a single human melanoma cell line M4Be. Using an in vitro clonogenic assay and provided that cells were cultured for no more than five passages, variations in cellular radioresistance of M4Be and seven sublines derived from M4Be were detected. This study shows a positive correlation between the cell intrinsic radioresistance of M4Be and its seven sublines and their total ganglioside content. More precisely, the proportion of radioresistant cells in M4Be and the seven sublines correlated with the number of cells determined by flow cytometry that were positively labelled with a monoclonal antibody directed to GD3 disialoganglioside. Blocking the cellular biosynthesis of gangliosides with the inhibitor Fumonisin B1 or cleaving with Vibrio cholerae neuraminidase the cell surface ganglioside-bound sialic acid in a radioresistant poorly metastatic subline increased its radiosensitivity in vitro. In contrast, enrichment of a radiosensitive metastatic subline with exogenous bovine brain GM1 increased its radioresistance in vitro. These results suggest that, in the radiation dose range important for radioprotection (0-1 Gy), membrane gangliosides radioprotect human melanoma cells in vitro.

Topics: Animals; Antibodies, Monoclonal; Cattle; Cell Death; Cell Survival; Clone Cells; Cobalt Radioisotopes; Dose-Response Relationship, Radiation; Flow Cytometry; Fumonisins; G(M1) Ganglioside; Gamma Rays; Gangliosides; Humans; Lung Neoplasms; Melanoma; Mycotoxins; Neuraminidase; Particle Accelerators; Radiation-Protective Agents; Radiation, Ionizing; Rats; Rats, Wistar; Transplantation, Heterologous; Tumor Cells, Cultured; Tumor Stem Cell Assay; Vibrio cholerae