CDKN2A and neoplasm: Additional genetic and epigenetic alterations are involved in the gradual loss of tissue homeostasis during tumour progression, among them epigenetic silencing of the tumour suppressor Cdkn2a (coding for a cell cycle and apoptosis control gene), Dkk1 and Sfrp family genes (coding for Wnt antagonists) or Hic1 (coding for a developmental control gene) [24], [25].