Isothiocyanates suppress the invasion and metastasis of tumors by targeting FAK/MMP-9 activity

Abstract

Isothiocyanates, which are present as glucosinolate precursors in cruciferous vegetables, have strong activity against various cancers. Here, we compared the anti-metastatic effects of isothiocyanates (benzyl isothiocyanate (BITC), phenethyl isothiocyanate (PEITC), and sulforaphane (SFN)) by examining how they regulate MMP-9 expression. Isothiocyanates, particularly PEITC, suppressed 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced MMP-9 activity and invasion in various cancer cell lines. By contrast, N-methyl phenethylamine, a PEITC analog without an isothiocyanate functional group, had no effect. A reporter gene assay demonstrated that BITC, PEITC, and SFN suppressed TAP-induced MMP-9 expression by inhibiting AP-1 and NF-κB in U20S osteosarcoma cells. All three compounds reduced phosphorylation of FAK, ERK1/2, and Akt. In addition, MMP-9 expression was downregulated by inhibiting FAK, ERK1/2, and Akt. Isothiocyanates-mediated inhibition of FAK phosphorylation suppressed phosphorylation of ERK1/2 and Akt in U2OS and A549 cells, along with the translocation of p65 and c-Fos, suggesting that isothiocyanates inhibit MMP-9 expression and cell invasion by blocking phosphorylation of FAK. Furthermore, isothiocyanates, abolished MMP-9 expression and tumor metastasis in vivo with the following efficacy: PEITC>BITC>SFN. Thus, isothiocyanates act as anti-metastatic compounds that suppress MMP-9 activity/expression by inhibiting NF-κB and AP-1 via suppression of the FAK/ERK and FAK/Akt signaling pathways.