Effect of ZSTK474, a Novel Phosphatidylinositol 3-Kinase Inhibitor, on DNA-Dependent Protein Kinase

Abstract

Phosphatidylinositol 3-kinase (PI3K) has been implicated in a variety of diseases including cancer. A number of PI3K inhibitors have recently been developed for use in cancer therapy. ZSTK474 is a highly promising antitumor agent targeting PI3K. We previously reported that ZSTK474 showed potent inhibition against four class I PI3K isoforms but not against 140 protein kinases. However, whether ZSTK474 inhibits DNA-dependent protein kinase (DNA-PK), which is structurally similar to PI3K, remains unknown. To investigate the inhibition of DNA-PK, we developed a new DNA-PK assay method using Kinase-Glo. The inhibition activity of ZSTK474 against DNA-PK was determined, and shown to be far weaker compared with that observed against PI3K. The inhibition selectivity of ZSTK474 for PI3K over DNA-PK was significantly higher than other PI3K inhibitors, namely NVP-BEZ235, PI-103 and LY294002. These results indicated that ZSTK474 was the most specific agent among these PI3K inhibitors.

ZSTK474, a novel phosphatidylinositol 3-kinase inhibitor identified using the JFCR39 drug discovery system

“…ZSTK474 was found to be a class I-specific PI3K inhibitor, by displaying selectivity over mTOR, DNA-PK, and other PI3K superfamily members. This characteristic is similar to that of GDC-0941, but different from NVP-BEZ235, which showed more potent activity against mTOR and DNA-PK than against class I PI3K [9,65] . We also examined the growth inhibition profiles of these PI3K inhibitors across the JFCR39 panel and compared their fingerprints.…”

Phosphoproteomic characterization of DNA damage response in melanoma cells following MEK/PI3K dual inhibition

“…Early strategies for targeting PI3K coinhibited the activities of ATM and PRKDC (31,32). PI3K-mTOR dual inhibitors (e.g., NVP-BEZ235, PI-103) also reportedly inhibit ATM and PRKDC in biochemical and cell-culture models (33,34). Used here, GDC-0941 is a pan-class I PI3K inhibitor with enzyme IC 50 values of 0.003 μM (p110α), 0.033 μM (p110β), 0.003 μM (p110δ), or 0.075 μM (p110γ), making it >400 times more selective for p110α/δ than PRKDC (16).…”

Combined inhibition of PI3K-related DNA damage response kinases and mTORC1 induces apoptosis in MYC-driven B-cell lymphomas

“…23 In cellular systems, mTOR inhibition was reported in the low nanomolar range, 23 and at submicromolar concentrations, potent inhibition of DNA PK 38,39 and ATM 40 has been described. To determine whether BEZ235 killed Em-Myc lymphomas at on-target concentrations, a panel of primary lymphomas was treated and assessed for apoptosis by annexin-V/PI staining at 24 hours ( Figure 2A; supplemental Figure 1A).…”

“…on May 13, 2018. by guest www.bloodjournal.org From BEZ235 is a PI3K superfamily inhibitor that antagonizes all PI3K isoforms, rapamycin-sensitive (mTORC1) and -insensitive (mTORC2) complexes, 23 and the PI3K-related DDR kinases, including DNA-PK 38,39 and ATM/ATR 40 ( Figure 1; Table 1). To determine which PI3K family kinases are functionally regulated by BEZ235 in Em-Myc lymphomas, we next profiled the inhibitory effects of BEZ235 on a range of PI3K-related phosphorylation substrates, using Everolimus as a comparator.…”