Indeed, truncated BRCA1 has been shown to antagonize wild-type BRCA1 function in a dominant-negative manner (Fan et al., 2001; Sylvain et al., 2002), and several lines of evidence support the view that truncated APC contributes to colorectal cancer by causing spindle misalignment that eventually leads to chromosomal instability (Fodde et al., 2001; Tighe et al., 2004; Quyn et al., 2010). This evidence concerns the gene APC and colorectal cancer.