Isomers of a marine diterpene distinguish sublines of human melanoma cells on the basis of apoptosis, cell cycle arrest and differentiation markers.

The action of the marine furanoditerpenes, spongiatriol (SP) and episopongiatriol (ESP), were compared in two sublines of human melanoma cells (MM96E and MM96L) derived from the same metastatic lesion. MM96E had higher tyrosinase activity and lower expression of alkaline phosphatase but was otherwise indistinguishable from MM96L. SP and ESP treatment of both cell lines for 72 h at cytostatic doses inhibited B8G3 expression and tyrosinase activity but had little effect on the expression of tyrosinase antigen. MM96L cells were affected more than MM96E. SP and ESP induced apoptosis in both cell lines, ESP causing dendritic morphology in a proportion of MM96L cells. SP induced a marked G2/M arrest in MM96E cells. SP and ESP together define subtle qualitative and quantitative differences in human melanoma phenoypes, possibly based on expression of a repertoire of neurotransmitter receptors.