Melatonin enhances anti-tumoral effects of menadione on colon cancer cells

KOHAN R; COLLIN A; ARECO V; TOLOSA DE TALAMONI N; PICOTTO G

Buenos Aires

Congreso; Reunión conjunta de Sociedades de Biociencias. LXII Reunión Anual de la SAIC; 2017

Colon cancer is one of the most important causes of death in entire world. New pharmacological strategies are always needed, especially in resistant variants of this pathology. We have previously reported that oxidant drugs such as menadione (MEN) or D,L-buthionine-S,R-sulfoximine (BSO) increase tumour cell sensibility, due to their well known ability to reduce glutathione (GSH) content. Besides, melatonin (MEL), a hormone regulating circadian rhythms, has antioxidant and antiapoptotic properties at low concentrations, while at high doses it has been shown to inhibit the growth of tumor cells. The aim of this study was to evaluate the the effects of MEN and MEL on the proliferation of colon cancer cells. Caco-2 cells (human colon adenocarcinoma) were treated with MEN, MEL, both or vehicle (ethanol). Cell proliferation was evaluated by crystal violet staining. Superoxide anion, glutathione levels (GSH) and nitric oxide (NO) levels were measured by spectrophotometry. Nuclear morphology was evaluated by Hoechst staining and cell migration by the wound healing assay. Statistically analyses: one way ANOVA and Bonferroni as a post-hoc test. MEN and MEL inhibited Caco-2 growth and this effect was time and dose-dependent. The antiproliferative effect began at 48 h being higher at 96 h. The concentration used for the next set of experiments was 20 µM and 750 µM for MEN and MEL, respectively. Total GSH levels decreased at 6 h with MEN, which was blocked by MEL. Superoxide anion increased by MEN, and the NO production was increased by MEN, MEL and MEN+MEL. The combined treatment caused morphological nuclear changes, compatible with cell death. Cell migration was decreased by all treatments. In conclusion, MEL enhances the antiproliferative effect of MEN on Caco-2 cells mainly via nitrosative stress and arrest of cell migration. This combination might be useful as a tool for intestinal cancer therapy.