In Vitro

Kinase Assay: A high-throughput screening cell-based assay is developed using MDA-MB-468 cells to detect mTORC1 and mTORC2 activity. Cells are exposed for 2 hours to increasing concentrations of AZD8055. At the end of the incubation period, cells are fixed, washed, and probed with antibodies against S473 pAkt or against S235/236 phosphorylated S6 (pS6). Levels of phosphorylation are assessed using an Acumen laser scanning cytometer.

Cell Assay: Cells (U87MG, A549 and H838 cells) are exposed to AZD8055 for 72 to 96 hours and stained for cell nuclei (0.03 mg/mL Hoechst 33342) and acidic vesicles (1 μg/mL acridine orange). Images are captured at 450 and 536 nm on an ArrayScan II platform, and the percentage of acidic vesicles and the number of cells are quantified. For LC3 assessment, cells are exposed to e64d/pepstatin (10 μg/mL) for 30 to 90 min before incubation with AZD8055. Cells are lysed on ice and analyzed by immunoblotting.

AZD8055 shows low activity (∼1,000-fold) against all PI3K isoforms (α, β, γ, δ) and other members of the PI3K-like kinase family (ATM and DNA-PK). AZD8055 inhibits the phosphorylation of mTORC1 (p70S6K and 4E-BP1) as well as phosphorylation of the mTORC2 (Akt) and downstream proteins. The rapamycin-resistant T37/46 phosphorylation sites on 4E-BP1 can be fully inhibited by AZD8055, resulting in significant inhibition of cap-dependent translation. AZD8055 potently inhibits proliferation in U87MG, A549 and H838 cells with IC50 of 53, 50 and 20 nM, respectively. AZD8055 also induces autophagy and increased LC3-II levels in H838 and A549 cells. AZD8055 decreases AML blast cell proliferation and cell cycle progression, reduces the clonogenic growth of leukemic progenitors and induces caspase-dependent apoptosis in leukemic cells but not in normal immature CD34+ cells. AZD8055 indicates inhibitory against the pediatric preclinical testing program (PPTP) cell lines with IC50 of 24.7 nM and induces significant differences in EFS distribution.