One of the essential regulators of this pathway that is significantly altered in GBMs (30–40%) is the PTEN tumour suppressor gene1, 3, which encodes a phosphatase responsible for the removal of phosphate from the 3′ position of the phospholipid second messenger phosphatidylinositol-3,4,5-trisphosphate, thus opposing mitogenic signalling mediated by class 1 phosphatidylinositol 3-OH kinases4. This evidence concerns the gene PTEN and neoplasm.