Abstract
Since a portion of patients with nasopharyngeal carcinoma (NPC) do not benefit much from current standard treatments, it is still needed to discover new therapeutic drugs to improve the prognosis of the patients. Considering that Chinese traditional medicine plays a role in inhibiting tumor progression, in this study, we aimed to investigate whether a Chinese herbal formula, Qing Yan Li Ge Tang (QYLGT), has the anticancer activity in NPC cells and explore the underlying mechanism as well. MTT assay, colony formation assay, immunoblotting assay, and DNA laddering assay were performed to assess cell viability, cell colony formation, protein expression, and DNA fragmentation, respectively. Results show that QYLGT was able to inhibit the cell viability and decrease colony formation ability in NPC cells. QYLGT could also increase the formation of intracellular vacuoles and induce the autophagy-related protein expressions, including Atg3, Atg6, and Atg12-Atg5 conjugate in NPC cells. Treatment with an autophagy inhibitor, 3-methyladenine, could significantly recover QYLGT-inhibited cell viability of NPC cells. In addition, QYLGT did not significantly induce apoptosis in NPC cells. We also found that QYLGT had the ability to activate phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of the rapamycin (mTOR) pathway. Treatment with PI3K inhibitors, LY294002 and wortmannin, or mTOR inhibitors, rapamycin and Torin 1, could not only recover QYLGT-inhibited cell viability of NPC cells but also inhibit Atg3 expression. Taken together, our results demonstrated that QYLGT could induce autophagic cell death in NPC cells through the PI3K/Akt/mTOR pathway.