Bardoxolone methyl blocks the efflux of Zn2+ by targeting hZnT1 to inhibit the proliferation and metastasis of cervical cancer

Cervical cancer is the second most prevalent malignancy in female reproductive system and a major cause of morbidity and mortality worldwide. Its proliferation and migration are closely associated with cellular zinc (Zn2+), which is meticulously regulated by the human Zn2+ importers (Zrt-/Irt-like proteins, hZIPs) and exporters (zinc transporters, hZnTs). Among them, hZnT1, the only Zn2+ transporter located on the cell membrane, exports Zn2+ from the cytosol to extracellular milieu and is significantly up-regulated in cervical cancer. Hence, deciphering the physiological function of hZnT1 and developing therapeutic agents that specifically target this transporter could be an effective strategy for cervical cancer treatment. Here, we determined the cryo-EM structure of hZnT1 and identified the critical residues involved in Zn2+ transport. Based on this structure, we performed virtual screening and found that Bardoxolone methyl (CDDO-ME) potently inhibits Zn2+ transport mediated by hZnT1. The complex structure and molecular dynamic simulations of hZnT1-CDDO-ME further elucidated the blocking mechanism, wherein CDDO-ME binds precisely above the Zn2+ site in the transmembrane region, effectively impeding the efflux of Zn2+. The cellular and animal experiments demonstrated that CDDO-ME specifically targets hZnT1, effectively suppressing the proliferation and migration of cervical tumors, with low toxicity and excellent biosafety. This study presents, for the first time, definitive experimental evidences demonstrating a close relationship between hZnT1 and the proliferation and migration of cervical cancer cells. Moreover, it provides valuable insight into the feasibility of hZnT1 as a novel therapeutic target and presents a promising agent for the treatment of cervical cancer.