In vitro effects of 2,5 hexanedione on a melanoma cell line: a morphological study

The effect of 2,5 hexanedione (2,5 HD) on a cultured human melanoma cell line (JR8) was explored. The addition of the toxicant at noncytolitic concentrations (0.08-0.16%) to the monolayers for 24 and 48 h, resulted in an irreversible inhibition of cell proliferation. Cessation of melanoma cell proliferation was accompanied by wide changes in morphological features of cells still adhering to the substrate. Incubation with the toxicant seemed to induce a differentiative process characterized mainly by a significant increase in cell protrusions. Melanoma cells, losing their bipolar appearance, often increased cell size and developed long dendritic and axon-like processes sometimes ramified in distal portions. Electron microscopic observations established that a change in the polarized appearance of control cells often occurred with 2,5 HD treatment and that a regular arrangement of organelles and cytoskeletal elements was detectable within these dendritic and axon-like protrusions. Furthermore, immunocytochemical studies confirmed an involvement of microtubules and actin network within cell prolongations. After the differentiative process a necrotizing effect occurred, inducing a progressive loss of viable, dendritic cells after 4 or 5 days. Incubation with cyclic AMP was ineffective in control cells while after 2,5 HD treatment seemed to increase the survival rate of neuronal-like cells. Possible mechanisms for the growth inhibitory and differentiative effects of 2,5 HD were discussed.