The LncRNA H19-Derived miR-675 Promotes Liver Necroptosis by Targeting FADD

Chronic inflammation is closely linked to cancer formation. Many molecular pathways are involved in the inflammatory response and some of these including microRNAs, have been connected to liver cancer development. The H19 derived microRNA-675 (miR-675) has been implicated as both tumor promoter and tumor suppressor and also plays a role in liver inflammation, which is not yet fully understood. We found that miR-675 promotes cell death in human hepatocellular carcinoma (HCC) cell lines. We show that FADD, a mediator of apoptotic and cell death signaling, is a miR-675 target and is down regulated by this miRNA. Importantly, we found a negative correlation between miR-675 and FADD expression in mouse models of HCC and in human samples. We demonstrated in a mouse model of liver inflammation that over expression of miR-675 repressed FADD expression and promoted necrosis. We confirmed that this necrotic cell death is necroptosis which can be inhibited by the necroptosis specific inhibitor. We also showed that necroptosis induced by miR-675 expression, is mediated by p-MLKL (Mixed Lineage Kinase Domain Like Pseudokinase) in a LPS induced liver inflammation. Furthermore, miR-675 enhanced MLKL binding to RIP3 (receptor-interacting protein 3), a key signaling molecule in necroptosis and inhibited cleaved caspase-8 & 3, suggesting that miR-675 induced a “shift” from apoptotic cellular cascades to a necroptotic cellular pathway. We propose that this regulation cascade could stimulate and enhance the inflammatory response in the liver, making miR-675 an important regulator in liver inflammation and potentially also in HCC.