Discovery, Synthesis, and Activity Evaluation of Novel Five-Membered Sulfur-Containing Heterocyclic Nucleosides as Potential Anticancer Agents In Vitro and In Vivo.

A series of novel five-membered sulfur-containing heterocyclic nucleoside derivatives were designed, synthesized, and evaluated for their anticancer activities in vitro and in vivo. The structure-activity relationship studies revealed that some of them showed obvious antitumor activities in several cancer cell lines. Among them, compound 22o exhibited remarkable antiproliferative activity against HeLa cells and was more potent than cisplatin (IC₅₀ = 2.80 vs 7.99 μM). Furthermore, mechanism studies indicated that 22o inhibited cell metastasis, induced cell apoptosis, decreased mitochondrial membrane potential, and activated autophagy through the PI3K-Akt-mTOR signaling pathway. Moreover, drug affinity responsive target stability and the cellular thermal shift assay revealed that 22o targeted RPS6 and inhibited its phosphorylation. Importantly, 22o inhibited the growth of the HeLa xenograft mouse model with a low systemic toxicity. These results indicated that 22o may serve as potent anticancer agents that merit further attention in future anticancer drug discovery.