WJD008, a Dual Phosphatidylinositol 3-Kinase (PI3K)/Mammalian Target of Rapamycin Inhibitor, Prevents PI3K Signaling and Inhibits the Proliferation of Transformed Cells with Oncogenic PI3K Mutant

The phosphatidylinositol-3-kinase (PI3K)-protein kinase B (Akt)-mammalian target of rapamycin (mTOR) signaling pathway is often constitutively activated in various human cancers, providing validated targets for cancer therapy. Among a series of 5-cyano-6-morpholino-4-substituted-pyrimidine analogs designed and synthesized based on PI3K target, 4-(2-(dimethylamino)vinyl)-2-(3-hydroxyphenyl)-6-morpholinopyrimidine-5-carbonitrile (WJD008) was selected for further pharmacological characterization because of its potent activity against PI3K signaling. WJD008 inhibited kinase activity of PI3K alpha and mTOR with less activity against PIKK family members. In cellular settings, WJD008 abrogated insulin-like growth factor-I-activated PI3K-Akt-mTOR signaling cascade and blocked the membrane translocation of a pleckstrin homology domain containing enhanced green fluorescent protein-general receptor for phosphoinositides, isoform 1-pleckstrin homology fusion protein, suggesting down-regulation of phosphatidylinositol (3,4,5)-trisphosphate output induced by WJD008 resulted in inactivation of PI3K pathway. Consequently, WJD008 arrested cells in G 1 phase without induction of apoptosis. Furthermore, WJD008 reversed the hyperactivation of the PI3K pathway caused by the oncogenic mutation of p110 alpha H1047R and suppressed the proliferation and clonogenesis of transformed RK3E cells harboring this mutant. WJD008 was superior to the pan-PI3K inhibitor wortmannin against proliferation of a panel of cancer cells independently of their status of PI3K pathway or tissue originations. In summary, WJD008 is a potent dual PI3K/mTOR modulator with antiproliferative and anticlonogenic activity in tumor cells and transformed cells with PIK3CA mutant, which provides new clues for the design and development of this chemical scaffold as an anticancer drug.