The genes in primary tumours with extremely high levels of methylated promoters in these cancers are PGP9.5, CCNA1, and NMDAR2B. These are proposed tumour suppressor genes: with PGP9.5 able to bind and stabilise p53 by preventing its proteasomal degradation; and NMDAR2B and CCNA1 acting to facilitate apoptosis (Waraya et al., 2015). Here, CCNA1 is linked to cancer.