Enhanced suppression of proliferation and migration in highly-metastatic lung cancer cells by combination of valproic acid and coumarin-3-carboxylic acid and its molecular mechanisms of action.

Valproic acid (VPA) as a broad-spectrum inhibitor of histone deacetylase, has been used in cancer therapy. Recently, the combination of VPA with other anticancer agents has been considered as a useful and necessary strategy to inhibit tumor growth and progression. The coumarin derivates from natural plants have been shown to be the promising natural anticancer agents. However, no literature is available on the anticancer effects of the combination of VPA and coumarin-3-carboxylic acid (HCCA). Here we show that this combination significantly increases inhibitory effects against the proliferation and migration in highly-metastatic lung cancer cells by inducing apoptosis and cell cycle arrest as well as regulating related protein expressions. Our results indicate that this combination of VPA with HCCA not only enhances the protein levels of Bax, cytosolic cytochrome c, caspase-3 and PARP-1 but also reduces the protein expressions of Bcl-2, cyclin D1 and NF-κB as well as inhibits the phosphorylation and expressions of Akt, EGFR, VEGFR2 and c-Met in the cancer cells. Our results suggest that the combination of VPA with HCCA suppresses the proliferation and migration of lung cancer cells via EGFR/VEGFR2/c-Met-Akt-NF-κB signaling pathways; this combination may have a wide therapeutic and/or adjuvant therapeutic application in the treatment of lung cancer.