At the Crossroads of TNF α Signaling and Cancer

Tumor necrosis factor-alpha (TNFα) is a pleiotropic pro-inflammatory cytokine of the TNF superfamily. It regulates key cellular processes such as death, and proliferation besides its well-known role in immune response through activation of various intracellular signaling pathways (such as MAPK, Akt, NF-κB, etc.) via complex formation by ligand-activated TNFα receptors. TNFα tightly regulates the activity of key signaling proteins via their phosphorylation and/or ubiquitination which culminate in specific cellular responses. Deregulated TNFα signaling is implicated in inflammatory diseases, neurological disorders, and cancer. TNFα has been shown to exert opposite effects on cancer cells since it activates prosurvival as well as anti-survival pathways depending on various contexts such as cell type, concentration, cell density, etc. A detailed understanding of TNFα signaling phenomena is crucial for understanding its pleiotropic role in malignancies and its potential as a drug target or an anticancer therapeutic. This review enlightens complex cellular signaling pathways activated by TNFα and further discusses its role in various cancers.

The role of MLKL in Hepatic Ischemia-Reperfusion Injury of Alcoholic Steatotic Livers

Alcohol-related liver disease (ALD) and non-alcoholic fatty liver disease (NAFLD) are the primary causes of chronic liver disease in western countries. Liver transplantation is currently one of the most efficient approaches to save patients with liver failure, which is often associated with hepatic ischemia-reperfusion (IR) injury. IR injury is exacerbated by hepatic steatosis, yet the mechanism remains elusive. Necroptosis is a form of regulated cell death mediated by receptor-interacting protein kinase 1 (RIP1), RIP3 and mixed lineage kinase domain-like (MLKL) protein, which has been implicated in the pathogenesis of ALD and NAFLD. Though necroptosis plays an important role in IR injury of high fat diet - induced steatotic livers, the role of necroptosis in IR injury of ethanol - induced steototic livers has not been investigated. In the present study, we used chronic plus binge alcohol (Gao-binge) feeding followed by IR surgery to investigate IR liver injury with ethanol-associated steatosis. We found that the levels of key necroptotic proteins MLKL and RIP3 increased in alcohol-fed mouse livers. Moreover, we observed increased liver injury after IR in control diet-fed mice, which was further exacerbated by alcohol feeding based on serum alanine aminotransferase (ALT) levels and TUNEL staining of necrotic cells. Hepatic neutrophil infiltration also increased in alcohol-fed mice after IR surgery. However, deletion of Mlkl did not protect against IR liver injury in alcohol-fed mice compared with matched wild-type mice. In conclusion, alcoholic steatosis promotes IR injury, which seems to be independent of MLKL-mediated necroptosis.