PTEN and cancer: Since the discovery of the RAS, RAF, MEK, PIK3CA, and AKT oncogenes and NF1, DUSP5, PP2A, PTEN, TSC1 and TSC2 tumor suppressor genes, the Ras/Raf/MEK/ERK and Ras/PI3K/PTEN/Akt/mTOR signaling cascades have been extensively investigated with the ultimate goal of determining how these genes become activated/inactivated and whether it is possible to suppress their activity in cancer and other growth-related diseases [1-6].