Protocatechuic acid inhibits cancer cell metastasis involving the down-regulation of Ras/Akt/NF-κB pathway and MMP-2 production by targeting RhoB activation.
OBJECTIVE
Protocatechuic acid (PCA) is plentiful in edible fruits and vegetables and is thus one anti-oxidative component of normal human diets. However, the molecular mechanisms involved in the chemopreventive activity of PCA are poorly understood. Here, we investigated the mechanism(s) underlying the anti-metastatic potential of PCA.


METHODS
We used AGS cells in a wound healing model and Boyden chamber assays in vitro and injection of B16/F10 melanoma cells in mice (metastasis model in vivo) to analyse the effect of PCA on cancer cell invasion and metastasis. The activities and expression of molecular proteins were measured by zymographic assay, real-time RT-PCR and Western blotting.


RESULTS
PCA inhibited cell migration and invasion at non-cytotoxic concentrations. Decreased expression of matrix metalloproteinase (MMP)-2 and a coincident increase in tissue inhibitor of MMP followed treatment with PCA. The PCA-inhibited MMP-2 activity and expression was accompanied by inactivation of NF-κB. All these effects of PCA could be mediated via the RhoB/ protein kinase Cε (PKCε) and Ras/Akt cascade pathways, as demonstrated by inhibition of PKCε and transfection of PKCε siRNA and ras overexpression vector. Finally, PCA inhibited metastasis of B16/F10 melanoma cells to the liver in mice.


CONCLUSIONS
Our data imply that PCA down-regulated the Ras/Akt/NF-κB pathway by targeting RhoB activation, which in turn led to a reduction of MMP-mediated cellular events in cancer cells and provides a new mechanism for the anti-cancer activity of PCA.
Lin
Hui-Hsuan
HH
School of Medical Laboratory and Biotechnology, Chung Shan Medical University, Taichung, Taiwan.
Chen
Jing-Hsien
JH
Chou
Fen-Pi
FP
Wang
Chau-Jong
CJ
D000818:Animals; D016588:Anticarcinogenic Agents / Q000494:pharmacology / Q000627:therapeutic use*; D015153:Blotting, Western; D015536:Down-Regulation / Q000187:drug effects*; D024202:Electrophoretic Mobility Shift Assay; D062385:Hydroxybenzoates / Q000494:pharmacology / Q000627:therapeutic use*; D047468:Immunoprecipitation; D020778:Matrix Metalloproteinase 2 / Q000096:biosynthesis*; D008546:Melanoma, Experimental / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism*; D009362:Neoplasm Metastasis / Q000517:prevention & control*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018631:ras Proteins / Q000378:metabolism*; D020743:rhoB GTP-Binding Protein / Q000378:metabolism*
D016588:Anticarcinogenic Agents; D062385:Hydroxybenzoates; D016328:NF-kappa B; C009091:protocatechuic acid; D051057:Proto-Oncogene Proteins c-akt; D020778:Matrix Metalloproteinase 2; D018631:ras Proteins; D020743:rhoB GTP-Binding Protein