NOX4 and hepatocellular carcinoma: In contrast, two studies demonstrated that low expression of NOX4 was associated with poor prognosis; interestingly, both of these studies (Eun et al. [10] and Ha et al. [12]) were conducted on hepatocellular carcinoma, whereas another study (Eun et al. [11]) on hepatocellular carcinoma also revealed the opposite result.