Guibitang, a traditional herbal medicine, induces apoptotic death in A431 cells by regulating the activities of mitogen-activated protein kinases

BACKGROUND Guibi-tang (GBT), a traditional herbal formula, mainly has been shown to possess immune regulation, antioxidant and protective effect of the gastric mucosa. Constituent herbs of GBT are frequently used to treat various diseases; however, their pharmacological effects, especially on cancer cells, differ from those of GBT. Furthermore, the molecular mechanisms behind effects of GBT remain unclear. In the present study, we explored the mechanism of chemopreventive/chemotherapeutic efficacy of GBT against human squamous cell carcinoma without cytotoxicity in normal cells and proved the efficacy of GBT through performing in vivo xenograft assay. METHODS For analysis of the constituents of GBT, high performance liquid chromatography (HPLC)-DAD system was performed. To detect the anticancer effect of GBT, cell viability assay, caspase activity assay, cell cycle analysis, DNA fragmentation analysis, and Western blot analysis were performed in A431 cells. In addition, the inhibitory effect of tumor growth by GBT was evaluated in athymic nude mice inoculated with A431 cells. RESULTS GBT showed cytotoxic activity against three different squamous cell carcinoma, especially on A431 cells. GBT induced the apoptosis through activating the caspase-8 in A431 cells. Inhibition of A431 cell growth by GBT was caused by G1-phase arrest through regulating proteins associated with cell cycle progression, such as cyclin D1, p21, and p27. Furthermore, GBT regulated the activation of mitogen-activated protein kinases (MAPKs) including extracellular signal-regulated kinase (ERK), p38 and c-Jun NH2-terminal kinase (JNK), and activated p53, a tumor suppressor protein. In MAPKs inhibitor study, inhibitors respectively blocked GBT-induced cell viability, indicating that MAPKs signals play critical role in cell death caused by GBT. In vivo xenografts, daily oral administration of 600 mg/kg GBT efficiently suppressed the tumorigenic growth of A431 cells without side effects such as loss of body weight and change of toxicological parameters compared to vehicle. CONCLUSIONS We first elucidate that GBT stimulates the apoptotic signaling pathway and suppresses the proliferation of A431 cells via regulating MAPKs signaling pathway. Furthermore, GBT significantly inhibits tumor growth of A431 cells without causing systemic toxicity. Based on our study, GBT could be useful in the management of skin cancer as chemoprevention and chemotherapy remedy.