PRNP and cancer: PrPC is involved in the progression of a number of cancers, including colorectal (Liang et al., 2006; Mehrpour and Codogno, 2010), breast (Diarra‐Mehrpour et al., 2004; Vassallo et al., 2005), gastric (Liang et al., 2006, 2007; Pan et al., 2006), and pancreatic (Li et al., 2009a), as well as potentially supporting drug resistance in gastric and breast cancers (Du et al., 2005; Li et al., 2009b).