Quercetin-3-methyl ether inhibits esophageal carcinogenesis by targeting the AKT/mTOR/p70S6K and MAPK pathways

Esophageal squamous cell carcinoma (ESCC) is highly prevalent in Asia, especially in China. Research findings indicate that nitrosamines, malnutrition, unhealthy living habits, and genetics contribute to esophageal carcinogenesis. Currently, the 5-year survival rate for ESCC patients remains low, owing in part to a lack of a clear understanding of mechanisms involved. Chemoprevention using natural or synthesized compounds might be a promising strategy to reduce esophageal cancer incidence. The epidermal growth factor receptor (EGFR) can activate downstream pathways including the phosphatidylinositol 3-kinase (PI3K) pathway and the Ras/mitogen-activated protein kinase (MAPK) pathways. Among the important players, AKT and ERKs have an important relationship with cancer initiation and progression. Here, we found that phosphorylated (p)-AKT and p-ERKs were highly expressed in esophageal cancer cell lines and in esophageal cancer patients. Human phospho-kinase array and pull-down assay results showed that quercetin-3-methyl ether (Q3ME) is a natural flavonoid compound that interacted with AKT and ERKs and inhibited their kinase activities. At the cellular level, Q3ME attenuated esophageal cancer cell proliferation and anchorage-independent growth. Western blot analysis showed that this compound suppressed the activation of AKT and ERKs downstream signaling pathways, subsequently inhibiting activating protein-1 (AP-1) activity. Importantly, Q3ME inhibited the formation of esophageal preneoplastic lesions induced by N-nitrosomethylbenzylamine (NMBA). The inhibition by Q3ME was associated with decreased inflammation and esophageal cancer cell proliferation in vivo. Collectively, our data suggest that Q3ME is a promising chemopreventive agent against esophageal carcinogenesis by targeting AKT and ERKs.