Antitumor and apoptosis-inducing effects of α-mangostin extracted from the pericarp of the mangosteen fruit (Garcinia mangostana L.) in YD-15 tongue mucoepidermoid carcinoma cells

alpha-mangostin is a dietary xanthone which has been shown to have antioxidant, anti-allergic, antiviral, antibacterial, anti-inflammatory and anticancer effects in various types of human cancer cells. In the present study, we aimed to elucidate the molecular mechanisms responsible for the apoptosis-inducing effects of alpha-mangostin on YD-15 tongue mucoepidermoid carcinoma cells. The results from MTT assays revealed that cell proliferation significantly decreased in a dose-dependent manner in the cells treated with alpha-mangostin. DAPI staining illustrated that chromatin condensation in the cells treated with 15 mu M alpha-mangostin was far greater than that in the untreated cells. Flow cytometric analysis indicated that alpha-mangostin suppressed YD-15 cell viability by inducing apoptosis and promoting cell cycle arrest in the sub-G1 phase. Western blot analysis of various signaling molecules revealed that alpha-mangostin targeted the extracellular signal-regulated kinase 1/2 (ERK1/2) and p38 mitogen-activated protein kinase (MAPK) signaling pathways through the inhibition of ERK1/2 and p38 phosphorylation in a dose-dependent manner. alpha-mangostin also increased the levels of Bax (pro-apoptotic), cleaved caspase-3, cleaved caspase-9 and cleaved-poly(ADP-ribose) polymerase (PARP), whereas the levels of the anti-apoptotic factors, Bcl-2 and c-myc, decreased in a dose-dependent manner. The anticancer effects of alpha-mangostin were also investigated in a tumor xenograft mouse model. The alpha-mangostin-treated nude mice bearing YD-15 tumor xenografts exhibited a significantly reduced tumor volume and tumor weight due to the potent promoting effects of alpha-mangostin on cancer cell apoptosis, as determined by TUNEL assay. Immunohistochemical analysis revealed that the level of cleaved caspase-3 increased, whereas the Ki-67, p-ERK1/2 and p-p38 levels decreased in the alpha-mangostin-treated mice. Taken together, the findings of our study indicate that alpha-mangostin induces the apoptosis of YD-15 tongue carcinoma cells through the ERK1/2 and p38 MAPK signaling pathways.