ABSTRACT
OBJECTIVE To investigate the effect and mechanism of gracillin from Reineckia carnea on autophagy in non- small cell lung cancer A549 cells. METHODS Using A549 cells as subjects， the effects of different concentrations of gracillin （0.25， 0.5， 1， 2， 4 μmol/L） on the proliferation of cells were detected by CCK-8 after being treated for different time （12， 24， 48 h）. Compared with the control group without medication， the effect of gracillin （2 μmol/L） on the formation of autophagosomes in cells was observed by transmission electron microscope after 24 h of exposure. The aggregation of GFP-LC3 on autophagosome membrane was detected by GFP-LC3 plasmid transfection after being treated with gracillin （0.25， 0.5， 1， 2 μmol/L） for 24 h. Quantitative real-time PCR and Western blot assay were used to detect the mRNA and protein expressions of family with sequence similarity 102 member A（FAM102A）， the expressions of autophagy-related proteins [p62， Beclin-1， microtubule-associated protein 1 light chain 3B （LC3B）]， and the expressions of phosphoinositide 3-kinase （PI3K）/protein kinase B （Akt） signaling pathway-related proteins in A549 cells after being treated with gracillin （0.25， 0.5， 1 and 2 μmol/L） for 24 h. RESULTS Gracillin significantly inhibited the proliferation of A549 cells in a concentration- and time-dependent manner. The IC50 was 2.55 μmol/L at 24 h. After 24 h of gracillin treatment， autophagosomes with bilayer membrane structure were found in the cell cytoplasm， and GFP-LC3 green fluorescent spots on autophagosome membrane were obvious， representing an increasing trend as drug concentration. Compared with the control group， mRNA and protein expressions of FAM102A （0.5， 1， 2 μmol/L groups）， protein expression of Beclin-1 （1， 2 μmol/L groups） and LC3B-Ⅱ/LC3B-Ⅰ ratio （2 μmol/L group） were significantly increased in different concentrations of gracillin groups， while the protein expression of p62 （1， 2 μmol/L groups）， and the protein phosphorylations of Akt （1， 2 μmol/L groups） and PI3K （2 μmol/L group） were all decreased significantly （P＜0.05 or P＜0.01）. CONCLUSIONS Gracillin can promote excessive autophagy in A549 cells by up-regulating mRNA and protein expressions of FAM102A and inhibiting PI3K/Akt signaling pathway， thus inhibiting cell proliferation.