CYCLOHEXIMIDE-INDUCED APOPTOSIS IN MELANOMA-CELLS DERIVED FROM REGRESSING CUTANEOUS TUMORS OF SINCLAIR SWINE

The role of apoptosis in the spontaneous regression of Sinclair swine melanoma was investigated in vitro with swine melanoma cell lines. Gro wth characteristics and sensitivity to cycloheximide-induced apoptosis were determined in melanoma cell lines derived from tumours that were progressing or undergoing regression in vivo. In contrast to cell lin es derived from progressing tumours, those derived from regressing tum ours showed induction of apoptosis; this phenomenon was dependent on d ose but independent of cell growth stage in culture. Chromatin condens ation, cell shrinkage, and fragmentation into apoptotic bodies, as wel l as DNA fragmentation into large kilobase fragments, occurred in cell lines from regressing tumours but not from progressing tumours. These findings suggest that swine melanoma cells are inherently more sensit ive to cell death during tumour regression. The apoptosis-sensitive an d resistant cell lines will be important for further studies of the ro les of cell signalling pathways and gene expression in tumour regressi on. (C) 1996 W.B. Saunders Company Limited