RIPK4 and colorectal cancer: Liu and colleagues reported that RIPK4 is overexpressed in cervical squamous cell cancer, and RIPK4 knockdown in vitro reduced cell migration and invasion.17 Similarly, RIPK4 is overexpressed in skin, ovarian and colorectal cancers.16 However, Adams et al. found that RIPK4 is downregulated in keratinocytes of the hyperproliferative epithelium;39 in hepatocellular carcinoma and tongue squamous cell cancer, RIPK4 expression is also reported to be downregulated.40,41 The discordance among these studies suggested that in different tumours, RIPK4 has different carcinogenic mechanisms.