The NLRP3 inflammasome has a fundamental role in host defence against microbial pathogens and its deregulation may cause diverse inflammatory diseases. NLRP3 protein expression is a rate-limiting step for inflammasome activation, thus its expression must be tightly controlled to maintain immune homeostasis and avoid detrimental effects. However, how NLRP3 expression is regulated remains largely unknown. In this study, we identify E3 ubiquitin ligase TRIM31 as a feedback suppressor of NLRP3 inflammasome. TRIM31 directly binds to NLRP3, promotes K48-linked polyubiquitination and proteasomal degradation of NLRP3. Consequently, TRIM31 deficiency enhances NLRP3 inflammasome activation and aggravates alum-induced peritonitis in vivo. Furthermore, TRIM31 deficiency attenuates the severity of dextran sodium sulfate (DSS)-induced colitis, an inflammatory bowel diseases model in which NLRP3 possesses protective roles. Thus, our research describes a mechanism by which TRIM31 limits NLRP3 inflammasome activity under physiological conditions and suggests TRIM31 as a potential therapeutic target for the intervention of NLRP3 inflammasome related diseases.

Hepatocellular carcinoma (HCC) is one of the most prevalent malignant tumors worldwide, and it is always the consequence of chronic hepatitis and liver cirrhosis. The nucleotide-binding domain, leucine-rich family (NLR), pyrin-containing 3 (NLRP3) inflammasome has been shown to orchestrate multiple innate and adaptive immune responses. However, little is known about its role in cancer. This study was performed to investigate the role of the NLRP3 inflammasome in the development and progression of HCC. The expression of NLRP3 inflammasome components was analyzed in HCC tissues and corresponding non-cancerous liver tissues at both the mRNA and protein levels. Our data demonstrate that the expression of all of the NLRP3 inflammasome components was either completely lost or significantly downregulated in human HCC, and that the deficiency correlated significantly with advanced stages and poor pathological differentiation. In addition, our data provide an overview of the expression of NLRP3 inflammasome components in the multi-stage development of HCC and indicate a surprising link between deregulation of the NLRP3 inflammasome molecular platform and HCC progression. In conclusion, this study presents a dynamic expression pattern of NLRP3 inflammasome components in multi-stage hepatocarcinogenesis and demonstrates that deregulated expression of the inflammasome is involved in HCC progression.

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Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide. The incidence of HCC is strikingly higher in males than in females. The remarkable gender disparity suggests an important role for sex hormones in HCC pathogenesis. Recently, estrogen has emerged as a protective factor in the development and progression of HCC, but whether it prevents and attenuates HCC, and the mechanism of protection, have not been elucidated. The present study shows that expression of estrogen receptor (ER) β was significantly downregulated in HCC tissue compared with normal liver tissue; moreover, its expression level showed a significant negative correlation with disease progression and a positive correlation with the expression level of NLRP3 inflammasome components. In a previous study, we showed that loss of NLRP3 inflammasome in HCC tissue contributed to tumor progression, whereas the mechanism of its deregulation was not elucidated. In this study, we investigated the potential link between NLRP3 inflammasome and estrogen. Our data reveal that treatment with 17β-estradiol (E2) significantly inhibited the malignant behavior of HCC cells through E2/ERβ/ MAPK pathway-mediated upregulation of the NLRP3 inflammasome. This study shows a novel link between ERβ and the NLRP3 inflammasome in HCC progression, which provides a potentially valuable therapeutic strategy for treatment of HCC patients.

Resistance to anoikis and Epithelial-mesenchymal transition (EMT) are two processes critically involved in cancer metastasis. In this study, we demonstrated that after anchorage deprival, hepatocellular carcinoma (HCC) cells not only resisted anoikis, but also exhibited EMT process. Microarray expression profiling revealed that expression of miR-424-5p was significantly decreased in anoikis-resistant HCC cells. Ectopic overexpression of miR-424-5p was sufficient to reverse resistance to anoikis, block EMT process and inhibit malignant behaviors of HCC cells. Target analysis showed that a potent β-catenin inhibitor, ICAT/CTNNBIP1 was a direct target of miR-424-5p. Further study demonstrated that miR-424-5p reversed resistance to anoikis and EMT of HCCs by directly targeting ICAT and further maintaining the E-cadherin/β-catanin complex on the cellular membrance. In vivo study further demonstrated that miR-424-5p significantly inhibited the tumorigenicity of HCC cells in nude mice. Clinical investigation demonstrated that miR-424-5p was significantly downregulated in HCC tissues compared with that of the non-cancerous liver tissues, and this decreased expression of miR-424-5p was significantly correlated with higher pathological grades and more advanced TNM stages. Therefore, aberrant expression of miR-424-5p is critically involved in resistance to anoikis and EMT during the metastatic process of HCC, and its downregulation significantly contributes to liver cancer progression.