Obesity increases the risk of cancers, including hepatocellular carcinomas (HCC). However, the precise molecular mechanisms through which obesity promotes HCC development are still unclear. Recent studies have shown that gut microbiota may influence liver diseases by transferring its metabolites and components. Here, we show that the hepatic translocation of obesity-induced lipoteichoic acid (LTA), a Gram-positive gut microbial component, promotes HCC development by creating a tumor-promoting microenvironment. LTA enhances the senescenceassociated secretory phenotype (SASP) of hepatic stellate cells (HSC) collaboratively with an obesityinduced gut microbial metabolite, deoxycholic acid, to upregulate the expression of SASP factors and COX2 through Toll-like receptor 2. Interestingly, COX2-mediated prostaglandin E 2 (PGE 2) production suppresses the antitumor immunity through a PTGER4 receptor, thereby contributing to HCC progression. Moreover, COX2 overexpression and excess PGE 2 production were detected in HSCs in human HCCs with noncirrhotic, nonalcoholic steatohepatitis (NASH), indicating that a similar mechanism could function in humans. SIGNIFICANCE: We showed the importance of the gut-liver axis in obesity-associated HCC. The gut microbiota-driven COX2 pathway produced the lipid mediator PGE 2 in senescent HSCs in the tumor microenvironment, which plays a pivotal role in suppressing antitumor immunity, suggesting that PGE 2 and its receptor may be novel therapeutic targets for noncirrhotic NASH-associated HCC.

Accumulating evidence indicates that the senescence-associated secretory phenotype (SASP) contributes to many aspects of physiology and disease. Thus, controlling the SASP will have tremendous impacts on our health. However, our understanding of SASP regulation is far from complete. Here, we show that cytoplasmic accumulation of nuclear DNA plays key roles in the onset of SASP. Although both DNase2 and TREX1 rapidly remove the cytoplasmic DNA fragments emanating from the nucleus in pre-senescent cells, the expression of these DNases is downregulated in senescent cells, resulting in the cytoplasmic accumulation of nuclear DNA. This causes the aberrant activation of cGAS-STING cytoplasmic DNA sensors, provoking SASP through induction of interferon-β. Notably, the blockage of this pathway prevents SASP in senescent hepatic stellate cells, accompanied by a decline of obesity-associated hepatocellular carcinoma development in mice. These findings provide valuable new insights into the roles and mechanisms of SASP and possibilities for their control.

The linear ubiquitin chain assembly complex (LUBAC) plays a crucial role in activating the canonical NF-jB pathway, which is important for B-cell development and function. Here, we describe a mouse model (B-HOIP Dlinear ) in which the linear polyubiquitination activity of LUBAC is specifically ablated in B cells. Canonical NF-jB and ERK activation, mediated by the tumour necrosis factor (TNF) receptor superfamily receptors CD40 and TACI, was impaired in B cells from B-HOIP Dlinear mice due to defective activation of the IKK complex; however, B-cell receptor (BCR)-mediated activation of the NF-jB and ERK pathways was unaffected. B-HOIP Dlinear mice show impaired B1-cell development and defective antibody responses to thymus-dependent and thymus-independent II antigens. Taken together, these data suggest that LUBAC-mediated linear polyubiquitination is essential for B-cell development and activation, possibly via canonical NF-jB and ERK activation induced by the TNF receptor superfamily, but not by the BCR.

No abstract

Inhibition of mitogen-activated protein kinase/extracellular signal-regulated kinase kinase (MEK) represents a promising strategy for the discovery of a new generation of anticancer chemotherapeutics. Our synthetic efforts, beginning from the lead compound 2, were directed at improving antiproliferative activity against cancer cells as well as various drug properties. These efforts led to the discovery of N-{3-[3-cyclopropyl-5-(2-fluoro-4-iodophenylamino)-6,8-dimethyl-2,4,7-trioxo-3,4,6,7-tetrahydro-2H-pyrido[4,3-d]pyrimidin-1-yl]phenyl}acetamide dimethylsulfoxide solvate (GSK1120212, JTP-74057 DMSO solvate; 1), a selective and highly potent MEK inhibitor with improved drug properties. We further confirmed that the antiproliferative activity correlates with cellular MEK inhibition and observed significant antitumor activity with daily oral dosing of 1 in a tumor xenograft model. These qualities led to the selection of 1 for clinical development.