Regulation of different components from Ophiopogon japonicus on autophagy in human lung adenocarcinoma A549Cells through PI3K/Akt/mTOR signaling pathway.

Autophagy plays a dual role in the development of cancer, acting as both a tumor suppressor and a cell survival inducer. Ophiopogon japonicus (L.f) Ker-Gawl (OJ), as a traditional Chinese medicine, specially possesses remarkable anti-cancer activity in the clinical. Previously, studies have indicated that flavonoids (FOJ) and steroidal saponins (SSOJ) are the main active substances of OJ. However, the effects of FOJ and SSOJ on autophagy of A549 cells have not been fully elucidated. In this study, we found that the expressions of autophagy-related mediators (LC3-II/LC3-I ratio, Atg-3, Atg-7 and Beclin-1) were increased in A549 cells by the treatment with FOJ (7.9mg crude drug/mL) and SSOJ (12.2mg crude drug/mL). Meanwhile, FOJ or SSOJ could induce the up-regulation of LC3-II at both protein and mRNA levels. Moreover, we observed the cytoplasmic vaculoes which formed double-layered membranes and only some cytoplasmic organelles or myelin figures remained in FOJ or SSOJ-treated A549 cells for 24h by Transmission Electron Microscopy (TEM). Further detection about the PI3K/Akt/mTOR signaling pathway showed that the levels of PI3K, Akt and mTOR were significantly suppressed with the FOJ or SSOJ treatment. The 3-MA (an autophagy inhibitor) and LY294002 (a PI3K inhibitor) further confirmed the underlying mechanism in the FOJ or SSOJ-induced autophagy of A549 cells. Additionally, the pretreatment with FOJ and SSOJ increased the level of p53, whereas decreased the expression of Ki67. These findings suggested that FOJ or SSOJ could activate the autophagy of A549 cells, wherein the mechanism might be associated with their inhibition of PI3K/Akt/mTOR signaling pathway. Thus, FOJ or SSOJ could be a potential autophagy inducer to prevent the process of lung cancer.