Quercetin Enhances 5-Fluorouracil-Driven Cytotoxicity Dose-Dependently in A375 Human Melanoma Cells

Cutaneous melanoma (CM) represents a severe skin cancer with a rising incidence at present and limited treatment options. 5-Fluorouracil (5-FU) is widely used, including for CM; however, the innate resistance of this cancer to conventional therapy remains problematic. Quercetin (QUE) is a flavonoid that can sensitize cancer cells to antitumor agents such as 5-FU. However, the potential sensitization capability of CM cells to 5-FU has scarcely been determined, and is investigated herein. Therefore, A375 CM cells were tested in terms of their cell viability, cell confluence, and morphological changes. Their nuclear and cytoskeletal aspects, clonogenic potential, and in ovo properties were also followed. The results showed that the 50% inhibitory concentrations (IC50s) of 5-FU and QUE determined by a cell proliferation assay were 11.56 and 11.08 µM, respectively. The addition of QUE (10 µM) to 5-FU (5-50 µM) increased the cytotoxic potential. A significant decline in cell viability (up to 43.51%), the loss of cell confluence, chromatin condensation and nuclear dysmorphology, tubulin and F-actin constriction, and a suppressed clonogenic ability were noted. The QUE + 5-FU association was non-irritating to the chorioallantoic membrane and showed an antiangiogenic effect in ovo. Thus, our results highlight that combining QUE with 5-FU can enhance the cytotoxic effect of 5-FU in A375 melanoma cells and present a safe profile in ovo.