These results were confirmed by western blot experiments since MOMO-treated melanoma cells in mild acidic culture medium (pH 6.3) showed a significant increase of cleaved-caspase 3 expression when compared to control (Figure 6B); thus demonstrating the pro-apoptotic effects of pH-activated MOMO in tumor cells, similarly to the native climacostol (Buonanno et al., 2008; Perrotta et al., 2016; Zecchini et al., 2019). This evidence concerns the gene CASP3 and melanoma.