NADPH oxidase 4 facilitates progression of chondrosarcoma via generation of reactive oxygen species.

Nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4) is an enzyme that regulates reactive oxygen species (ROS) generation, and its function in the development of chondrosarcoma remains unclear. In the present study, we studied NOX4 expression in chondrosarcoma by immunochemical examination, and analyzed the role of NOX4 in viability and apoptosis of human chondrosarcoma cell line SW1353 using NOX4 siRNA or NOX4 inhibitor GKT137831. NOX4 level significantly increased in tumor compared to that in para-carcinoma sample. The levels of NOX4 were positively correlated with histological grade and Musculoskeletal Tumor Society stage of the patients. NOX4 level was significantly increased in SW1353 compared with that in chondrocytes CHON-001. Knockdown of NOX4 or inhibition of NOX4 by GKT137831 both decreased generation of ROS, and induced growth inhibition and apoptosis in SW1353, accompanied with the activation of caspases (caspase-3, caspase-8 and caspses-9), upregulation of Bax, cytochrome C(cyt-c), cleaved-PARP and down-regulation of Bcl-2. Moreover, NOX4 siRNA and GKT137831 decreased the expression of p-Akt, p-ERK and p-p65 in SW1353 cells. In an in vivo study, NOX4 shRNA transfected SW1353 have shown impaired growth ability compared to the SW1353 when they were injected into the nude mice. Meanwhile, GKT137831 induced growth inhibition and apoptosis in SW1353 xenograft animals, together with increased expression of Bax, cyt-c, cleaved-PARP, and decreased expression of Bcl-2, p-Akt, p-ERK and p-p65. NOX4 plays a positive role in the development of chondrosarcoma and could serve as a promising target against chondrosarcoma clinically.