Cancer metastasis is one of the most critical events in
cancer patients, and the median overall survival of stage IIIb or IV patients with metastatic
lung cancer in the TNM classification is only 8 or 5 months, respectively. We previously demonstrated that
Juzentaihoto, a Japanese
traditional medicine, can inhibit
cancer metastasis through the activation of macrophages and T cells in mouse
cancer metastatic models; however, the mechanism(s) through which
Juzentaihoto directly affects
tumor cells during the
metastasis process and which herbal components from
Juzentaihoto inhibit the metastatic potential have not been elucidated. In this study, we focused on the epithelial-to-mesenchymal transition (EMT), which plays an important role in the formation of
cancer metastasis. We newly determined that only the Cinnamomi Cortex (CC) extract, one of 10 herbal components of
Juzentaihoto, inhibits TGF-β-induced EMT. Moreover, the contents of
catechin trimer in CC extracts were significantly correlated with the efficacy of inhibiting TGF-β-induced EMT. Finally, the structure of the
catechin trimer from CC extract was chemically identified as
procyanidin C1 and the compound showed inhibitory activity against TGF-β-induced EMT. This illustrates that
procyanidin C1 is the main active compound in the CC extract responsible for EMT inhibition and that
procyanidin C1 could be useful as a lead compound to develop inhibitors of
cancer metastasis and other diseases related to EMT.