Inhibition of SIRT1 relieves hepatocarcinogenesis via alleviating autophagy and inflammation.

Imbalanced Sirtuin 1 (SIRT1) levels may lead to liver diseases through abnormal regulation of autophagy, but the roles of SIRT1-regulated autophagy in hepatocellular carcinoma are still controversial. In this study, we found that SIRT1 mRNA and protein levels were upregulated in hepatocellular carcinoma, and high SIRT1 expression hinted an advanced stage and a poor prognosis. The differentially expressed proteins were significantly elevated in autophagy, cellular response to stress, and immune signaling pathways. In a thioacetamide-induced hepatocellular carcinoma mouse model, we found that SIRT1 expression was highly increased with increased autophagy and excessive macrophage inflammatory response. Next, we established a Hepa 1-6 cells and macrophage co-culture system in vitro to model the alteration of tumor microenvironment, and found that the medium from CCl4-treated or SIRT1-overexpressing Hepa 1-6 cells triggered the polarization of macrophage M1, and the culture medium derived from M1 macrophage promoted Hepa 1-6 cells growth and intracellular oxidative stress. The progression of liver fibrosis in the CCl4-induced liver fibrosis mouse model showed that inhibition of SIRT1 alleviated inflammatory response and ameliorated liver fibrosis. These findings suggest that SIRT1-regulated autophagy and inflammation are oncogenic in hepatocarcinogenesis.

Autophagy suppression facilitates macrophage M2 polarization via increased instability of NF-κB pathway in hepatocellular carcinoma.

The tumor microenvironment is a highly heterogeneous circumstance composed of multiple components, while tumor-associated macrophages (TAMs) are major innate immune cells with highly plastic and are always educated by tumor cells to structure an advantageous pro-tumor immune microenvironment. Despite emerging evidence focalizing the role of autophagy in other immune cells, the regulatory mechanism of autophagy in macrophage polarization remains poorly understood. Herein, we demonstrated that hepatocellular carcinoma (HCC) cells educated macrophages toward M2-like phenotype polarization under the condition of coculture. Moreover, we observed that inhibition of macrophage autophagy promoted M2-like macrophage polarization, while the tendency was impeded when autophagy was motivated. Mechanistically, macrophage autophagy inhibition inactivates the NF-κB pathway by increasing the instability of TAB3 via ubiquitination degradation, which leads to the M2-like phenotype polarization of macrophages. Both immunohistochemistry staining using human HCC tissues and experiment in vivo verified autophagy inhibition is correlated with M2 macrophage polarization. Altogether, we illustrated that macrophage autophagy was involved in the process of HCC cells domesticating M2 macrophage polarization via the NF-κB pathway. These results provide a new target to interfere with the polarization of macrophages to M2-like phenotype during HCC progression.

Inhibition of autophagy in macrophage promotes IL-1ß-mediated hepatocellular carcinoma progression via inflammasome accumulation and self-recruitment.

Hepatocellular carcinoma (HCC) has a complex and changeable tumor microenvironment. Despite emerging evidence focusing on autophagy process within immune cells, the function and regulatory mechanism of macrophage autophagy in tumor progression remains unclear. Our results of multiplex-immunohistochemistry and RNA-sequencing identified the reduced levels of autophagy in tumor macrophages in the HCC microenvironment, associated with a poor prognosis and increased microvascular metastasis in HCC patients. Specifically, HCC suppressed the macrophage autophagy initiation through the up-regulation of mTOR and ULK1 phosphorylation at Ser757. Knockdown of autophagy-related proteins to further inhibit autophagy significantly boosted the metastatic potential of HCC. Mechanistically, the accumulation of NLRP3 inflammasome mediated by autophagy inhibition promoted the cleavage, maturation, and release of IL-1ß, which facilitated the HCC progression, eventually accelerating HCC metastasis via the epithelial-mesenchymal transition. Autophagy inhibition provoked macrophage self-recruitment through the CCL20-CCR6 signaling was also a crucial account of HCC progression. Recruited macrophages mediated the cascade amplification of IL-1ß and CCL20 to form a novel pro-metastatic positive feedback loop through promoting HCC metastasis and increased macrophage recruitment, respectively. Notably, targeting IL-1ß/IL-1 receptor signaling impaired lung metastasis induced by macrophage autophagy inhibition in a mice HCC lung metastasis model. In summary, this study highlighted that inhibition of tumor macrophage autophagy facilitated HCC progression by increasing IL-1ß secretion via NLRP3 inflammasome accumulation and by macrophage self-recruitment through the CCL20 signaling pathway. Interruption of this metastasis-promoting loop by IL-1ß blockade may provide a promising therapeutic strategy for HCC patients.