Curcumin potentiates the galbanic acid-induced anti-tumor effect in non-small cell lung cancer cells through inhibiting Akt/mTOR signaling pathway

Galbanic acid (GBA), which is known as a sesquiterpene coumarin, has been reported to have various anti-tumor activities in different cells. Our study intended to investigate whether curcumin potentiates GBA-induced anti-tumor effect in non-small cell lung cancer cells. The combined effect of GBA and curcumin on cell viability was examined by MTT analysis. Cellular apoptosis was evaluated by flow cytometry analysis. Autophagy was defined by autophagosome observed by confocal microscopy after infected with GFP-LC3 adenovirus. In addition, the expression of marker proteins involved in cell apoptosis, autophagy, and Akt/mTOR signaling pathway were estimated by qRT-PCR and Western Blotting assay. 15 μM curcumin combined with 40 μM GBA could obtain better synergistic repressive efficacy on cell viability and notably induced cell apoptosis in A549 cells. Besides, curcumin in alliance with GBA could significantly inhibit cell migration and invasion. GFP-LC3 infection experiments elaborated that curcumin could potentiate GBA induced cell autophagy and restrain the phosphorylation of Akt/mTOR/P70s6k signaling pathway. What's more, the reaction of migration, apoptosis, and autophagy induced by curcumin and GBA treatment could be reversed by mTOR inhibitor rapamycin and AKT activator insulin.