CDKN2A and glioblastoma: This inhibits the expression of p16/CDKN2 and leads to glioblastoma progression.98 The loss of PTEN expression through promoter hypermethylation activates the PI3K/AKT signalling pathway and increases the expression of the mucin-like transmembrane glycoprotein podoplanin (PDPN).32,33  PDPN promoter hypermethylation silences its expression and reduces the proliferation and migration of glioblastoma cells.33 The 5′ region of the TP53 gene does not contain a CpG island; however, a basal promoter region of 85 bp is essential for its full promoter activity.