Homodimers of Vanillin and Apocynin Decrease the Metastatic Potential of Human Cancer Cells by Inhibiting the FAK/PI3K/Akt Signaling Pathway

The spread of cancer cells to distant organs, in a process called metastasis, is the main factor that contributes to most death in cancer patients. Vanillin, the vanilla flavoring agent, has been shown to suppress metastasis in a mouse model. Here, we evaluated the antimetastatic potential of the food additive divanillin, the homodimer of vanillin, and their structurally related compounds, apocynin and diapocynin, in hepatocellular carcinoma cells. The Transwell invasion assay showed that the dimeric forms exhibited a potency higher than those of vanillin and apocynin in inhibiting invasion, with IC50 values of 23.3 ± 7.4 to 41.3 ± 4.2 μM for the dimers, which are 26–34-fold lower than IC50 values of vanillin and apocynin (p < 0.05). Both monomeric and dimeric forms target regulation of the invasion process by inhibiting phosphorylation of FAK and Akt. Molecular docking studies suggested that the dimers should bind more tightly than vanillin and apocynin to the Y397 pocket of the FAK FERM domain. Thus, the food additive divanillin has antimetastatic potential greater than that of the flavoring agent vanillin.