RESUMO
ObjectiveTo investigate the effect and underlying molecular mechanism of astragaloside-Ⅳ （AS-Ⅳ） on autophagy and apoptosis of nasopharyngeal carcinoma cells. MethodIn experiments in vitro， the effect of AS-Ⅳ on the autophagy of nasopharyngeal carcinoma cells was observed by monodansylcadaverine （MDC） staining and transmission electron microscopy （TEM）. In experiments in vivo， immunofluorescence （IF） and Western blot were used to detect the changes in autophagy and apoptosis and the expression of key proteins in the phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin （PI3K/Akt/mTOR） signaling pathway after the establishment of a xenograft tumor model in nude mice. ResultAfter 5-8F cells were treated with AS-Ⅳ of different doses （5， 10， 20 μmol·L-1）， the fluorescence intensity of autophagy in AS-Ⅳ groups significantly increased as compared with that in the blank group. The fluorescence expression of autophagy in AS-Ⅳ groups was the strongest after intervention for 24 hours， and the fluorescence expression in the 10 μmol·L-1 AS-Ⅳ group was the most obvious. The autophagy activator rapamycin （RAPA） induced more autophagosomes in 5-8F cells under the transmission electron microscope， and 3-methyladenine （3-MA）， an autophagy inhibitor， did not induce autophagosome formation in 5-8F cells under the transmission electron microscope as compared with the results in the blank group. In the 10 μmol·L-1 AS-Ⅳ group， the intracellular structure and cell membrane were intact and clear， and autophagosome formation was observed. Compared with the blank group， the AS-Ⅳ groups showed inhibited tumor volume （P<0.05， P<0.01）， potentiated fluorescence signals of microtubule-associated protein l light chain 3 type Ⅱ/microtubule-associated protein l light chain 3 type Ⅰ （LC3 Ⅱ/Ⅰ） and cleaved Caspase-3 （P<0.05， P<0.01）， increased expression levels of the mammalian homolog of yeast ATG6 （Beclin-1）， LC3 Ⅱ/Ⅰ， cleaved Caspase-3， and cleaved PARP （P<0.05， P<0.01）， down-regulated expression of ubiquitin-binding protein （p62） （P<0.05， P<0.01）， and reduced protein expression levels of phosphorylated PI3K （p-PI3K）， phosphorylated Akt （p-Akt）， and phosphorylated mTOR （p-mTOR） （P<0.05， P<0.01）. ConclusionAS-Ⅳ can induce autophagy and apoptosis of nasopharyngeal carcinoma cells， and the mechanism is presumably attributed to the activation of the PI3K/Akt/mTOR signaling pathway.