Novel anticancer inhibitors targeting the PI3K/Akt/mTOR signaling route and apoptosis inducers: A study on the apoptosis mechanism via the intrinsic mitochondrial-mediated pathway.

The PI3K/Akt/mTOR pathway is a key target for cancer due to its essential role in cell proliferation. This study developed quinoline compounds as a potent PI3Kδ/mTOR inhibitor and apoptosis inducer. The investigation found that 6i had the highest cytotoxicity against Raji and HeLa cells, with IC50s values of 0.18μM and 0.39μM, respectively. Further, 6i demonstrated substantial selectivity against dual targets PI3Kδ (IC50 = 0.034μM) and mTOR (IC50 = 0.047 μM). The kinase assay discovered that 6i had a greater selectivity for PI3Kδ/mTOR compared to PI3Ks (α, β, and γ). Molecular investigation revealed that 6i significantly reduced phosphorylated p-PI3K, p-Akt and p-RPS6 levels in Western blot, confirming PI3K/Akt/mTOR as the pathway of action. In addition, compound 6i stopped the cell cycle at the G0/G1 phase and raised total apoptosis by 16.26%. These findings were substantiated by morphological alterations in the AO/EB staining. Furthermore, 6i-treated cells increased intracellular ROS levels and reduced mitochondrial membrane polarization in a dose-dependent manner, indicating that apoptosis was mediated by a mitochondrial route. In addition, higher levels of Bax, Bax/Bcl-2 ratio, and cytochrome c also corroborated the fact that apoptosis was mediated via mitochondrial pathway. Also, treatment of compound increased fraction of caspase-3, caspase-9, and PARP-1 (excluding caspase-8), indicating that apoptosis was mediated via the intrinsic route. Besides, in silico studies had validated the anticancer effects of inhibiting PI3Kδ/mTOR. Moreover, 6i demonstrated a promising safety profile in hERG assay. Taken together, our finding suggest that 6i may be a potential candidate for further in vivo investigation.