The aim of this study was to investigate the mechanism of the anticancer activity of luteolin in metastatic human colon cancer SW620 cells. Luteolin dose-dependently reduced the viability and proliferation of SW620 cells and increased the expression of antioxidant enzymes. The expression of antiapoptotic protein Bcl-2 decreased whereas the expression of proapoptotic proteins Bax and caspase-3 increased by luteolin treatment, resulting in increased poly (ADP-ribose) polymerase (PARP) cleavage and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) positivity. Luteolin also increased the expression of autophagic proteins Beclin-1, autophagy-related protein 5 (Atg5) and microtubule-associated protein 1A/1B-light chain 3 beta-I/II (LC3B-I/II), while the usage of 3-methyladenine suggested a prosurvival role of autophagy. Moreover, treatment with luteolin induced reversal of the epithelial-mesenchymal transition process through the suppression of the wingless-related integration site protein (Wnt)/β-catenin pathway. The cytotoxic activity of luteolin coincided with the activation of extracellular signal-regulated kinase 1/2 (ERK1/2) and forkhead box O3a (FOXO3a). Treatment with the mitogen-activated protein kinase kinase (MEK) inhibitor PD0325901 inhibited ERK-dependent FOXO3a phosphorylation, resulting in increased FOXO3a expression and apoptosis, with the suppression of autophagy. The results of the current study suggest the antitumor activity of luteolin in SW620 cells through the ERK/FOXO3a-dependent mechanism, as well as its antimetastatic potential.
Keywords: Apoptosis; Autophagy; Colon cancer SW620 cells; Forkhead box O3a; Luteolin; Mitogen-activated protein kinase.
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