PIK3CA and neuroblastoma: Protein kinase signalling research in neuroblastoma has traditionally centred on the phosphatidylinositol-3 kinase (PI3K)/Akt and Ras/mitogen-activated protein kinase (MAPK) pathways, fundamental regulators of cell metabolism, growth, proliferation and survival, and two of the most commonly studied signalling pathways in human cancers [54,55].