We previously showed that RPS27L is an MDM2 binding protein whose overexpression inhibits MDM2-mediated p53 ubiquitylation, whereas its silencing reduces p53 in some cancer lines (e.g., A549 and SJSA), but not in others (e.g., SY5Y, MCF7, U2OS, HCT116, and RKO) (Xiong et al., 2011) (data not shown), suggesting RPS27L might act as a p53 activator in a cancer cell dependent manner. This evidence concerns the gene MDM2 and cancer.