Indeed, FEN1 is expressed at low levels in quiescent cells (Kim et al., 2000) but is highly expressed in proliferative tissues and cancers, including lung (Nikolova et al., 2009), breast (Singh et al., 2008), gastric (Wang et al., 2014), prostate (Lam et al., 2006), pancreatic (Iacobuzio‐Donahue et al., 2003), and brain cancers (Krause et al., 2005). Here, FEN1 is linked to cancer.