PTEN and melanoma: PI3K-Akt signalling is constitutively activated by mutant NRAS (Johnson and Puzanov, 2015), as well as the PTEN tumour suppressor which is found to be effected by loss of function mutations in approximately 20% of BRAF-mutant melanomas, resulting in Akt activation (Shull et al., 2012; Akbani et al., 2015).