" PTEN is an important tumour suppressor – a gene that appears to stop healthy cells from becoming cancerous – and it is switched off in around one in eight patients with melanoma and in almost half of those who carry a mutation in another cancer gene called BRAF. Scientists think one way melanoma cells can metastasise is by losing their PTEN function, increasing their shape-shifting ability and in turn enabling them to move to many different tissues within the body."

https://www.icr.ac.uk/news-features/latest-features/highlights-of-the-year/stopping-cancer-in-its-tracks