As accumulating evidences suggest close involvement of phosphatidylinositol 3-kinase (PI3K) in cancer, novel PI3K inhibitors such as ZSTK474, GDC-0941,NVP-BEZ235 and BKM-120 have been developed for cancer therapy.A high frequency ofhotspot mutations known as E542K, E545K and H1047R in the PIK3CA gene, which encodes the catalytic subunit of PI3K, has been found in various types of human cancers.The hotspot PIK3CA mutations also lead to resistance to therapeutics targeting epidermal growth factor receptor (EGFR), further suggesting that inhibition of hotspot mutant PIK3CA be required for a PI3K inhibitor as anticancer drug.