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Hepatocellular carcinoma and cholangiocarcinoma are the most common liver primary tumors and showed an increased incidence and mortality over the last decades. Due to a frequent late diagnosis, liver cancer is associated with limited curative therapeutic options. Characterizing new molecular determinants of liver carcinogenesis is required to develop innovative treatments and to identify clinically relevant biomarkers. Recently, circular RNAs (circRNAs) emerged as promising regulatory molecules involved in cancer onset and progression, thus opening new opportunities. Mechanistically, circRNAs are currently mainly described for their capability to sponge and to regulate the activity of microRNAs and RNA binding proteins, although other functions are emerging (e.g. transcriptional and post-transcriptional regulation, protein scaffolding). In liver cancer, circRNAs are described to regulate tumor cell proliferation, migration, invasion and cell death resistance. Their role in regulating angiogenesis, genome instability, immune surveillance and metabolic switching is emerging. Importantly, circRNAs are detected in body fluids. Due to their circular structure, circRNAs are often more stable than mRNAs or miRNAs and could therefore serve as promising biomarkers quantifiable with high specificity and sensitivity though minimally invasive methods. This review focuses on the role and the clinical relevance of circRNAs in liver cancer, including the development of innovative biomarkers and therapeutic strategies.

Background & Aims After invading intestinal epithelial cells, enteric bacteria encounter phagocytes, but little is known about how phagocytes internalize the bacteria to generate host responses. BAI1 (brain angiogenesis inhibitor 1) binds and internalizes Gram-negative bacteria through an engulfment and cell motility protein 1 (ELMO1)/Ras-related C3 botulinum toxin substrate 1 (Rac1)-dependent mechanism. We delineate the role of ELMO1 in host inflammatory responses after enteric infection. Methods ELMO1-depleted murine macrophage cell lines, intestinal macrophages, and ELMO1-deficient mice (total or myeloid-cell specific) were infected with Salmonella enterica serovar Typhimurium. The bacterial load, inflammatory cytokines, and histopathology were evaluated in the ileum, cecum, and spleen. The ELMO1-dependent host cytokines were detected by a cytokine array. ELMO1-mediated Rac1 activity was measured by pull-down assay. Results The cytokine array showed a reduced release of proinflammatory cytokines, including tumor necrosis factor-α (TNF-α) and monocyte chemoattractant protein 1 (MCP-1), by ELMO1-depleted macrophages. Inhibition of ELMO1 expression in macrophages decreased Rac1 activation (∼6-fold) and reduced internalization of Salmonella. ELMO1-dependent internalization was indispensable for TNF-α and MCP-1. Simultaneous inhibition of ELMO1 and Rac function virtually abrogated TNF-α responses to infection. Activation of nuclear factor κB, extracellular signal-regulated kinases 1/2, and p38 mitogen-activated protein kinases were impaired in ELMO1-depleted cells. Bacterial internalization by intestinal macrophages completely depended on ELMO1. Salmonella infection of ELMO1-deficient mice resulted in a 90% reduction in bacterial burden and attenuated inflammatory responses in the ileum, spleen, and cecum. Conclusions These findings suggest a novel role for ELMO1 in facilitating intracellular bacterial sensing and the induction of inflammatory responses after infection with Salmonella.

Invasive migration of carcinoma cells is a prerequisite for the metastatic dissemination of solid tumours. Numerous mechanisms control the ability of cancer cells to acquire a motile and invasive phenotype, and subsequently degrade and invade the basement membrane. Several genes that are up-regulated in breast carcinoma are responsible for mediating the metastatic cascade. Recent studies have revealed that the NFAT (nuclear factor of activated T-cells) is a transcription factor that is highly expressed in aggressive breast cancer cells and tissues, and mediates invasion through transcriptional induction of pro-invasion and migration genes. In the present paper we demonstrate that NFAT promotes breast carcinoma invasion through induction of GPC (glypican) 6, a cell-surface glycoprotein. NFAT transcriptionally regulates GPC6 induction in breast cancer cells and binds to three regulatory elements in the GPC6 proximal promoter. Expression of GPC6 in response to NFAT signalling promotes invasive migration, whereas GPC6 silencing with shRNA (small-hairpin RNA) potently blocks this phenotype. The mechanism by which GPC6 promotes invasive migration involves inhibition of canonical β-catenin and Wnt signalling, and up-regulation of non-canonical Wnt5A signalling leading to the activation of JNK (c-Jun N-terminal kinase) and p38 MAPK (mitogen-activated protein kinase). Thus GPC6 is a novel NFAT target gene in breast cancer cells that promotes invasive migration through Wnt5A signalling.

The HMGA2 (high-mobility group AT-hook) protein has previously been shown as an oncoprotein, whereas ectopic expression of HMGA2 is found to induce growth arrest in primary cells. The precise mechanisms underlying this phenomenon remain to be unravelled. In the present study, we determined that HMGA2 was able to induce apoptosis in WI38 primary human cells. We show that WI38 cells expressing high level of HMGA2 were arrested at G2/M phase and exhibited apoptotic nuclear phenotypes. Meanwhile, the cleaved caspase 3 (cysteine aspartic acid-specific protease 3) was detected 8 days after HMGA2 overexpression. Flow cytometric analysis confirmed that the ratio of cells undergoing apoptosis increased dramatically. Concurrently, other major apoptotic markers were also detected, including the up-regulation of p53, Bax and cleaved caspase 9, down-regulation of Bcl-2; as well as release of cytochrome c from the mitochondria. We further demonstrate that the shRNA (small-hairpin RNA)-mediated Apaf1 (apoptotic protease activating factor 1) silencing partially rescued the HMGA2-induced apoptosis, which was accompanied by the decrease of cleaved caspase-3 level and a decline of cell death ratio. Our results also reveal that γH2A was accumulated in nuclei during the HMGA2-induced apoptosis along with the up-regulation of cleaved caspase 2, suggesting that the HMGA2-induced apoptosis was dependent on the pathway of DNA damage. Overall, the present study unravelled a novel function of HMGA2 in induction of apoptosis in human primary cell lines, and provided clues for clarification of the mechanistic action of HMGA2 in addition to its function as an oncoprotein.

Recent studies have demonstrated a number of molecular mechanisms contributing to the initiation of cardiac hypertrophy response to pressure overload. IGF1R (insulin-like growth factor-1 receptor), an important oncogene, is overexpressed in hypertrophic heart and mediates the hypertrophic pathology process. In this study, we applied with liposomal magnetofection that potentiated gene transfection by applying an external magnetic field to enhance its transfection efficiency. Liposomal magnetofection provided high efficiency in transgene expression in vivo. In vivo, IGF1R-specific-shRNA (small-hairpin RNA) by magnetofection inhibited IGF1R protein expression by 72.2±6.8, 80.7±9.6 and 84.5±5.6%, at 24, 48 and 72 h, respectively, after pGFPshIGF1R injection, indicating that liposomal magnetofection is a promising method that allows the targeting of gene therapy for heart failure. Furthermore, we found that the treated animals (liposomal magnetofection with shIGF1R) showed reduced septal and posterior wall thickness, reduced HW:BWs (heart weight-to-body weights) compared with controls. Moreover, we also found that liposomal magnetofection-based shIGF1R transfection decreased the expression level of p-ERK (phosphorylated extracellular-signal-regulated kinase)1/2, p-AKT1 (phosphorylated protein kinase B1) compared with untreated hearts. These results suggested that liposomal magnetofection-mediated IGF1R-specific-shRNA may be a promising method, and suppression the IGF1R expression inhibited norepinephrine-induced cardiac hypertrophic process via inhibiting PI3K (phosphoinositide 3-kinase)/AKT pathway.

The free radical theory of aging proposes that ROS (reactive oxygen species) are major driving forces of aging, and are also critically involved in cellular senescence. Besides the mitochondrial respiratory chain, alternative sources of ROS have been described that might contribute to cellular senescence. Noxs (NADPH oxidases) are well-known sources of superoxide, which contribute to the antimicrobial capabilities of macrophages, a process involving the prototypical member of the family referred to as Nox2. However, in recent years non-phagocytic homologues of Nox2 have been identified that are involved in processes other than the host defence. Superoxide anions produced by these enzymes are believed to play a major role in signalling by MAPKs (mitogen-activated protein kinases) and stress-activated kinases, but could also contribute to cellular senescence, which is known to involve oxygen radicals. In HUVECs (human umbilical vein endothelial cells), Nox4 is predominantly expressed, but its role in replicative senescence of HUVECs remains to be elucidated. Using shRNA (small-hairpin RNA)-mediated knockdown of Nox4, implicating lentiviral vectors, we addressed the question of whether lifelong depletion of Nox4 in HUVECs would influence the senescent phenotype. We found a significant extension of the replicative lifespan of HUVECs upon knockdown of Nox4. Surprisingly, mean telomere length was significantly reduced in Nox4-depleted cells. Nox4 depletion had no discernable influence on the activity of MAPKs and stress-activated kinases, but reduced the degree of oxidative DNA damage. These results suggest that Nox4 activity increases oxidative damage in HUVECs, leading to loss of replicative potential, which is at least partly independent of telomere attrition.

Integrins are transmembrane alphabeta heterodimer receptors that function as structural and functional bridges between the cytoskeleton and ECM (extracellular matrix) molecules. The RGD (arginine-glycine-aspartate tripeptide motif)-dependent integrin alpha8beta1 has been shown to be involved in various cell functions in neuronal and mesenchymal-derived cell types. Its role in epithelial cells remains unknown.Integrin alpha8beta1 was found to be expressed in the crypt cell population of the human intestine but was absent from differentiating and mature epithelial cells of the villus. The function of alpha8beta1 in epithelial crypt cells was investigated at the cellular level using normal HIECs (human intestinal epithelial cells). Specific knockdown of alpha8 subunit expression using an shRNA (small-hairpin RNA) approach showed that alpha8beta1 plays important roles in RGD-dependent cell adhesion, migration and proliferation via a RhoA/ROCK (Rho-associated kinase)-dependent mechanism as demonstrated by active RhoA quantification and pharmacological inhibition of ROCK. Moreover, loss of alpha8beta1, through RhoA/ROCK, impairs FA (focal adhesion) complex integrity as demonstrated by faulty vinculin recruitment.Integrin alpha8beta1 is expressed in epithelial cells. In intestinal crypt cells, alpha8beta1 is closely involved in the regulation of adhesion, migration and cell proliferation via a predominant RhoA/ROCK-dependent mechanism. These results suggest an important role for this integrin in intestinal crypt cell homoeostasis.