Conditioned medium from lung carcinoma cell line A549 increases the viability of human umbilical vein endothelial cells by activating the PI3K-Akt1 pathway

Objective:To study the effects of the conditioned medium (CM) from human lung adenocarcinoma cell line A549 on the viability and apoptosis of human umbilical vein endothelial cells (HUVECs) and the role of PI3K-Akt signaling pathway in the process. Methods:HUVECs were cultured with CM of A549 cells. Cell viability was detected by XTT assay. The morphological changes of HUVECs were analyzed by Hoechst 33258 staining and fluorescence microscopy. The apoptosis was detected by flow cytometry. Expression levels of total Akt and phosphorylated Akt were assessed by Western blotting. PI3K inhibitors wortmannin(WT)and Akt1 siRNA(siAkt1)were used to block PI3K-Akt signaling pathway. The mRNA transcription of Akt subtype was determined by RT-PCR.Results:A549 CM significantly increased cell viability after 24 h treatment (P=0.037) and inhibited apoptosis (P=0.001) of HUVECs. CM time-dependently activated phosphorylation of Akt. Akt was phosphorylated at 15 min after CM treatment and reached the peak at 30 min and then tended to decline. Both WT and siAkt1 blocked the effects of CM. Conclusion:The CM of A549 cells increased the survival and inhibit the apoptosis of HUVECs. Akt1 played a significant role in the process.