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 IC_50s 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.