Downstream from hypoxia-induced caspase-1 activation, cleavage and release of proinflammatory cytokines interleukin (IL)-1β and -18 occurred. We further demonstrate that overexpression of HMGB1 or treatment with recombinant HMGB1 enhanced the invasiveness of HCC cells, whereas stable knockdown of HMGB1 remarkably reduced HCC invasion. Moreover, in a murine model of HCC pulmonary metastasis, stable R788 cell line knockdown of HMGB1 suppressed HCC invasion and metastasis. Conclusion: These results suggest

that in hypoxic HCC cells, HMGB1 activates TLR4- and RAGE-signaling pathways to induce caspase-1 activation with the subsequent production of multiple inflammatory mediators, which, in turn, promote cancer invasion and metastasis. (HEPATOLOGY 2012;55:1866–1875) A worldwide increase in mortality associated with hepatocellular carcinoma (HCC) has recently been reported.1 Clinical treatment of HCC remains challenging because of a lack of effective chemotherapy and clearly defined endpoints for clinical protocols.2, 3 The advanced nature of disease at presentation, often in the background of steatosis4 and chronic hepatitis C,5 is a major change in the etiology from that observed in

the past.6 The main cause of death in HCC patients, irrespective of etiology, is cancer metastasis within or outside the liver. The underlying mechanisms responsible for invasiveness and metastatic spread of HCC are still not fully understood. Afatinib mw Hypoxia is found in a wide range of human malignancies, including liver, breast, prostate, and pancreatic cancers as well RG7204 chemical structure as brain tumors and melanoma.7 The extent of hypoxia is associated with tumor progression and poor clinical outcomes. Hypoxia has a dual role: Insufficient oxygen limits tumor cell division while, at the same time, selecting for

more malignant cells and induces cell adaptations that allow for more invasive behavior.8 Cancer cells may promote tumor metastasis through the release of paracrine or endocrine signals that enhance invasiveness and promote the tumor premetastatic niche.9-11 Tumor-derived mediators not only inhibit apoptosis of tumor cells, but also promote cell invasiveness and metastasis. High-mobility group box 1 (HMGB1) is an evolutionarily conserved, chromatin-binding protein that has been implicated in several disease states, including sepsis, arthritis, ischemia-reperfusion injury, and cancer.12, 13 Cancer cells that have undergone necrotic cell death can release HMGB1 into the local microenvironment. HMGB1 is also actively secreted by inflammatory cells, acting as an endogenous danger signal and binding with high affinity to several receptors, including the receptor for advanced glycation endproducts (RAGE) as well as Toll-like receptors (TLRs)-2, -4, and -9.12 Extracellular HMGB1 can lead to chronic inflammatory-reparative responses that, in the setting of cancer, may lead to tumor cell survival, expansion, and metastases.