Novel Phenylmethylenecyclohexenone Derivatives as Potent TrxR Inhibitors Display High Antiproliferative Activity and Induce ROS, Apoptosis, and DNA Damage.

The natural product piperlonguminine (PL) has been shown to exert potential anticancer activity against several types of cancer via elevation of reactive oxidative species (ROS). However, the application of PL has been limited due to its poor water solubility and moderate activity. To improve PL's potency, we designed and synthesized a series of 17 novel phenylmethylenecyclohexenone derivatives and evaluated their pharmacological properties. Most of them exerted antiproliferative activities against four cancer cell lines with IC50 values lower than PL. Among these, compound 10e not only showed good water solubility and exerted the most potent antiproliferative activity against HGC27 cells (IC50 = 0.76 μM), which was 10-fold lower than PL (IC50 = 7.53 μM), but also exhibited lower cytotoxicity in human normal gastric epithelial cells GES-1 compared with HGC27 cells. Mechanistically, compound 10e inhibited thioredoxin reductase (TrxR) activity, increased ROS levels, and diminished mitochondrial transmembrane potential (MTP) in HGC27 cells. Furthermore, 10e also induced G2/M phase arrest, and triggered cancer cell apoptosis through the regulation of apoptotic proteins. Finally, 10e promoted DNA damage in HGC27 cells via the activation of the H2AX(S139ph) and p53 signaling. In conclusion, 10e, with prominent tumor selectivity and water solubility, could be a promising candidate for the treatment of cancer and, as such, warrants further investigation.