Ma_2023_Am.J.Physiol.Gastrointest.Liver.Physiol__

The endocannabinoid system (ECS) is dysregulated in various liver diseases. Previously we had shown that the major endocannabinoid 2-arachidonoyl glycerol (2-AG) promoted tumorigenesis of intrahepatic cholangiocarcinoma (ICC). However, biosynthesis regulation and clinical significance of 2-AG remain elusive. In present study we quantified 2-AG by gas chromatography/mass spectrometry (GC/MS) and showed that 2-AG was enriched in ICC patients' samples as well as in thioacetamide-induced orthotopic rat ICC model. Moreover, we found that diacylglycerol lipase beta (DAGLbeta) was the principal synthesizing enzyme of 2-AG which significantly upregulated in ICC. DAGLbeta promoted tumorigenesis and metastasis of ICC in vitro and in vivo, and positively correlated with clinical stage and poor survival in ICC patients. Functional studies showed that AP-1 (heterodimers of c-Jun and FRA1) directly binded to the promoter and regulated transcription of DAGLbeta, which can be enhanced by lipopolysaccharide (LPS). miR-4516 was identified as the tumor-suppressing miRNA of ICC which can be significantly suppressed by LPS, 2-AG or ectopic DAGLbeta overexpression. FRA1 and STAT3 were targets of miR-4516 and overexpression of miRNA-4516 significantly suppressed expression of FRA1, SATA3 and DAGLbeta. Expression of miRNA-4516 was negatively correlated with FRA1, SATA3 and DAGLbeta in ICC patients' samples. Our findings identify DAGLbeta as the principal synthesizing enzyme of 2-AG in ICC. DAGLbeta promotes oncogenesis and metastasis of ICC and is transcriptionally regulated by a novel AP-1/DAGLbeta/miR4516 feedforward circuitry.