NOX4 and neoplasm: In favour of this hypothesis, we recently found that NOX4 plays a role in regulating liver cell proliferation either under physiological conditions or during tumorigenesis.29 NOX4 silencing increases the tumorigenic potential of human HCC cells in xenografts in mice, resulting in earlier onset of tumour formation and increase in tumour size.29 Overall, results strongly suggested that NOX4 plays a growth inhibitory role.