Enhancing effect of natural borneol on the cellular uptake of demethoxycurcumin and their combined induction of G2/M arrest in HepG2 cells via ROS generation

•NB enhanced the antiproliferative activity of DCur.•DCur entered into the HepG2 cells by the pathway of TfR.•ROS was one cause of NB/DCur-induced cell cycle arrest in the G2/M phase. This study was to investigate whether natural borneol (NB) could enhance the anti-cancer effect of demethoxycurcumin (DCur) on HepG2 cell line by MTT assay, flow cytometry, and western blotting assay. Our results demonstrated that NB/DCur resulted in a significant decrease in cell viability due to pretreatment of NB enhancing the cellular uptake of DCur. Flow cytometric assay showed that NB/DCur-induced HepG2 cells growth inhibition was mainly caused by induction of G2/M arrest, as evidenced by accumulation of the G2/M cell population. Immunoblotting assay demonstrated that NB/DCur down-regulated expression levels of cdc2 and cyclin B1, which contributed to G2/M arrest. Moreover, NB/DCur elevated the level of intracellular reactive oxygen species (ROS), indicating that NB/DCur-induced G2/M arrest was achieved by triggered ROS-mediated DNA damage involving MAPK and Akt signaling pathways. Taken together, our results suggested that the combination of NB and DCur induced G2/M phase arrest in HepG2 through ROS overproduction. This study demonstrated that NB had the potential to be further developed into a chemosensitizer of DCur in the treatment of human cancers.