EFFECTS OF MELATONIN ON THE PROLIFERATION AND DIFFERENTIATION OF HUMAN NEUROBLASTOMA-CELLS IN CULTURE

Since melatonin has direct inhibitory effects on some tumor cells in v itro, the aim of the present work was to study whether the growth and structural characteristics of the human neuroblastoma cell line SK-N-S H in vitro are influenced by this indoleamine. Concentrations of melat onin of 10(-9) and 10(-11) M significantly inhibited (P < 0.05) cell p roliferation. Subphysiological (10(-13) M) or supraphysiological (10(- 7) and 10(-5) M) concentrations of melatonin lacked this effect. After 8 days of exposure to melatonin (10(-9) M), cells showed significantl y smaller cell and nuclear sizes than control cells. Melatonin-treated cells presented greater-neurite outgrowth than control cells. These r esults support the hypothesis that melatonin, at physiological concent rations, exerts a direct antiproliferative effect on SK-N-SH cells, pr omoting the differentiation of neuroblastoma cells.