BackgroundRecent studies have emphasized causative links between microRNAs (miRNAs) deregulation and tumor development. In hepatocellular carcinoma (HCC), more and more miRNAs were identified as diagnostic and prognostic cancer biomarkers, as well as additional therapeutic tools. This study aimed to investigate the functional significance and regulatory mechanism of the miR-199a2/214 cluster in HCC progression.Methods and FindingsIn this study, we showed that miR-214, as well as miR-199a-3p and miR-199a-5p levels were significantly reduced in the majority of examined 23 HCC tissues and HepG2 and SMMC-7721 cell lines, compared with their nontumor counterparts. To further explore the role of miR-214 in hepatocarcinogenesis, we disclosed that the ER stress-induced pro-survival factor XBP-1 is a target of miR-214 by using western blot assay and luciferase reporter assay. Re-expression of miR-214 in HCC cell lines (HepG2 and SMMC-7721) inhibited proliferation and induced apoptosis. Furthermore, ectopic expression of miR-214 dramatically suppressed the ability of HCC cells to form colonies in vitro and to develop tumors in a subcutaneous xenotransplantation model of the BALB/c athymic nude mice. Moreover, reintroduction of XBP-1s attenuated miR-214-mediated suppression of HCC cells proliferation, colony and tumor formation. To further understand the mechanism of the miR-199a/214 cluster down-expression in HCC, we found that thapsigargin (TG) and tunicamycin (TM) or hypoxia-induced unfolded protein response (UPR) suppresses the expression of the miR-199a/214 cluster in HCC cells. By promoter analysis of the miR-199a2/214 gene, we conjectured NFκB as a potential negative regulator. We further found that UPR and LPS-induced NFκB activation suppressed miR-199a2/214 transcription, and this suppression was reversed by NFκB inhibition in HCC cells.ConclusionsOur study suggest that modulation of miR-214 levels may provide a new therapeutic approach for cancer treatment and revealed that UPR may offer a new explanation for why the miR-199a/214 cluster were down-regulated in the progression in HCC.

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Prolonged endoplasmic reticulum (ER) stress causes apoptosis and is associated with heart failure. Whether CYP2J2 and its arachidonic acid metabolites [epoxyeicosatrienoic acids (EETs)] have a protective influence on ER stress and heart failure has not been studied. Assays of myocardial samples from patients with end-stage heart failure showed evidence of ER stress. Chronic infusion of isoproterenol (ISO) or angiotensin II (AngII) by osmotic mini-pump induced cardiac hypertrophy and heart failure in mice as evaluated by hemodynamic measurements and echocardiography. Interestingly, transgenic (Tr) mice with cardiomyocyte-specific CYP2J2 expression were protected against heart failure compared with wild-type mice. ISO or AngII administration induced ER stress and apoptosis, and increased levels of intracellular Ca 21 . These phenotypes were abolished by CYP2J2 overexpression in vivo or exogenous EETs treatment of cardiomyocytes in vitro. ISO or AngII reduced sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA2a) expression in hearts or isolated cardiomyocytes; however, loss of SERCA2a expression was prevented in CYP2J2 Tr hearts in vivo or in cardiomyocytes treated with EETs in vitro. The reduction of SERCA2a activity was concomitant with increased oxidation of SERCA2a. EETs reversed SERCA2a oxidation through increased expression of antioxidant enzymes and reduced reactive oxygen species levels. Tempol, a membrane-permeable radical scavenger, similarly decreased oxidized SERCA2a levels, restored SERCA2a activity, and markedly reduced ER stress response in the mice treated with ISO. In conclusion, CYP2J2-derived EETs suppress ER stress response in the heart and protect against cardiac failure by maintaining intracellular Ca 21 homeostasis and SERCA2a expression and activity.