PTEN and cancer: In fact, elevated ROS production is not limited to cancer cells that harbour a RAS oncogene but has also been observed in cancer cells that harbour a mutation in another gene of the RAS or the phosphatidylinositol-3 kinase (PI3K) pathway (NF1, PIK3CA, PTEN) or an upstream tyrosine kinase (Met or BCR-ABL)[44-51].