ZNF660 and pachyonychia congenita: Our previous study also showed that the promoter‐associated CpG islands of the two genes ST6(alpha‐N‐acetyl‐neuraminyl‐2,3‐beta‐galactosyl‐1,3)‐N‐acetylgalactosaminide alpha‐2,6‐sialyltransferase 3 (ST6GALNAC3) and zinc finger protein 660 (ZNF660) were significantly hypermethylated in PC versus benign prostate tissue in two small sample sets (Haldrup et al., 2013).