Luteoloside Suppresses Proliferation and Metastasis of Hepatocellular Carcinoma Cells by Inhibition of NLRP3 Inflammasome

The inflammasome is a multi-protein complex which when activated regulates caspase-1 activation and IL-1 beta secretion. Inflammasome activation is mediated by NLR proteins that respond to stimuli. Among NLRs, NLRP3 senses the widest array of stimuli. NLRP3 inflammasome plays an important role in the development of many cancer types. However, Whether NLRP3 inflammasome plays an important role in the process of hepatocellular carcinoma (HCC) is still unknown. Here, the anticancer effect of luteoloside, a naturally occurring flavonoid isolated from the medicinal plant Gentiana macrophylla, against HCC cells and the underlying mechanisms were investigated. Luteoloside significantly inhibited the proliferation of HCC cells in vitro and in vivo. Live-cell imaging and transwell assays showed that the migration and invasive capacities of HCC cells, which were treated with luteoloside, were significantly inhibited compared with the control cells. The inhibitory effect of luteoloside on metastasis was also observed in vivo in male BALB/c-nu/nu mouse lung metastasis model. Further studies showed that luteoloside could significantly reduce the intracellular reactive oxygen species (ROS) accumulation. The decreased levels of ROS induced by luteoloside was accompanied by decrease in expression of NLRP3 inflammasome resulting in decrease in proteolytic cleavage of caspase-1. Inactivation of caspase-1 by luteoloside resulted in inhibition of IL-1 beta. Thus, luteoloside exerts its inhibitory effect on proliferation, invasion and metastasis of HCC cells through inhibition of NLRP3 inflammasome. Our results indicate that luteoloside can be a potential therapeutic agent not only as an adjuvant therapy for HCC, but also, in the control and prevention of metastatic HCC.