Sulforaphane inhibits epithelial-mesenchymal transition by activating extracellular signal-regulated kinase 5 in lung cancer cells

Abstract

Epithelial-mesenchymal transition (EMT) contributes to the initiation, invasion, metastasis and drug resistance of cancer. The function of extracellular signal-regulated kinase 5 (ERK5) in lung cancer progression remains elusive. In this study, we investigated the effect of sulforaphane (SFN) on lung cancer EMT and the role of ERK5 in its effect. Wound healing and Transwell assays were applied to examine the migratory and invasive capacity in vitro. Quantitative real-time polymerase chain reaction and immunoblotting analysis were performed to investigate the expression of mRNA and protein levels. Small-interfering RNA was used to silence ERK5. Xenograft model was used to confirm the effect of SFN in vivo. Enhanced EMT and decreased ERK5 activation were observed in lung cancer cells in comparison with normal human bronchial epithelial cells. SFN diminished the migratory and invasive capacity of lung cancer cells. Additionally, significantly increased expression of epithelial markers (E-cadherin and ZO-1), decreased expression of mesenchymal markers (N-cadherin and Snail1) and activation of ERK5 were observed after SFN treatment. The inhibitory effect of SFN on lung cancer cell EMT was attenuated by ERK5 silencing. SFN-induced EMT suppression and ERK5 activation were further confirmed in lung cancer xenograft mouse model. The present study illustrated for the first time that ERK5 activation mediates SFN suppression of lung cancer cell EMT. These findings could provide new insights into the function of ERK5 in EMT regulation and the potential therapeutic application of SFN in cancer intervention.

Keywords: AP-1; ERK5; Epithelial–mesenchymal transition; Lung cancer; Sulforaphane.