Substitution of S225, but not S278, with alanine (A) almost eliminated the slower-migrating, upper band of SIX1, and abolished pSer and pS225 signals, and the cancer-related SIX1 (Q177R) mutant had similar pattern to wild-type (WT) SIX1 in terms of pSer and pS225 signals (Fig. 1b).17 These data indicates that S225 is the major phosphorylation site of SIX1. Here, SIX1 is linked to cancer.