Sulforaphane suppresses EMT and metastasis in human lung cancer through miR-616-5p-mediated GSK3β/β-catenin signaling pathways

Sulforaphane is a common antioxidant selectively abundant in cruciferous plants, which exhibits effective anti-cancer actions in control of tumorigenesis or progression of various cancers. A recent study has shown that sulforaphane attenuates the EGFR signaling pathway in non-small cell lung cancer (NSCLC), suggesting its potential anti-metastatic effects. In this study we assessed the involvement of sulforaphane and miR-616-5p in epithelial-mesenchymal transition (EMT) and NSCLC metastasis. Sulforaphane suppressed the cell proliferation in human NSCLC cell lines H1299, 95C and 95D with IC₅₀ values of 9.52±1.23, 9.04±1.90 and 17.35±2.03 μmol/L, respectively. At low concentrations (1–5 μmol/L), sulforaphane dose-dependently inhibited the migration and invasion of 95D and H1299 cells with relatively high metastatic potential. The anti-metastatic action of sulforaphane was confirmed in 95D and H1299 cell xenografts in vivo. In fresh NSCLC tissue samples from 179 patients, miR-616-5p levels were upregulated in late-stage NSCLCs, and strongly correlated with risk of NSCLC recurrence and metastasis. Consistent with the clinic observation, miR- 616-5p levels in the 3 NSCLC cell lines were correlated with their metastatic ability, and were decreased by sulforaphane treatment. Silencing miR-616-5p markedly suppressed the migration and invasion of 95D cells in vitro and NSCLC metastasis in vivo. Further studies revealed that miR-616-5p directly targeted GSK3β and decreased its expression, whereas sulforaphane decreased miR-616-5p levels by histone modification, and followed by inactivation of the GSK3β/β-catenin signaling pathway and inhibition of EMT, which was characterized by loss of epithelial markers and acquisition of a mesenchymal phenotype in NSCLC cells. Our findings suggest that sulforaphane is a potential adjuvant chemotherapeutic agent for the prevention of NSCLC recurrence and metastasis, and miR-616-5p can be clinically utilized as a biomarker or therapeutic target to inhibit metastasis.