Note added in proof Antonio Sarikas, Technische Universitaet Muenchen (TUM) 13 May 2011 Recently, Pei et al. reported that deletion of the Parc (Cul9) gene in Mus musculus resulted in spontanous tumor development. Pei XH, Bai F, Li Z, Smith MD, Whitewolf G, Jin R, Xiong Y. Cytoplasmic CUL9/PARC Ubiquitin Ligase Is a Tumor Suppressor and Promotes p53-Dependent Apoptosis. Cancer Res. 2011; 71: 2969-77. Competing interests None.