Background & Aims-The tumor suppressor PTEN inhibits AKT2 signaling; both are aberrantly expressed in liver tumors. We investigated how PTEN and AKT2 regulate liver carcinogenesis. Loss of PTEN leads to spontaneous development of liver tumors from progenitor

Aims Circular RNAs (circRNAs) are involved in gene regulation in a variety of physiological and pathological processes. The present study aimed to investigate the effect of circRNA_000203 on cardiac hypertrophy and the potential mechanisms involved. Methods and results CircRNA_000203 was found to be up-regulated in the myocardium of Ang-II-infused mice and in the cytoplasma of Ang-II-treated neonatal mouse ventricular cardiomyocytes (NMVCs). Enforced expression of circRNA_000203 enhances cell size and expression of atrial natriuretic peptide and β-myosin heavy chain in NMVCs. In vivo, heart function was impaired and cardiac hypertrophy was aggravated in Ang-II-infused myocardium-specific circRNA_000203 transgenic mice (Tg-circ203). Mechanistically, we found that circRNA_000203 could specifically sponge miR-26b-5p, -140-3p in NMVCs. Further, dual-luciferase reporter assay showed that miR-26b-5p, -140-3p could interact with 3′-UTRs of Gata4 gene, and circRNA_000203 could block the above interactions. In addition, Gata4 expression is transcriptionally inhibited by miR-26b-5p, -140-3p mimic in NMVCs but enhanced by over-expression of circRNA_000203 in vitro and in vivo. Functionally, miR-26b-5p, -140-3p, and Gata4 siRNA, could reverse the hypertrophic growth in Ang-II-induced NMVCs, as well as eliminate the pro-hypertrophic effect of circRNA_000203 in NMVCs. Furthermore, we demonstrated that NF-κB signalling mediates the up-regulation of circRNA_000203 in NMVCs exposed to Ang-II treatment. Conclusions Our data demonstrated that circRNA_000203 exacerbates cardiac hypertrophy via suppressing miR-26b-5p and miR-140-3p leading to enhanced Gata4 levels.

Insulin signaling in the liver leads to accumulation of phosphatidylinositol (3,4,5)-trisphosphate (PIP 3 ). Deletion of the phosphatase Pten (phosphatase and tensin homologue deleted on chromosome 10) reduces PIP 3 levels and leads to fatty liver development. The purpose of this study was to investigate the mechanisms underlying lipogenesis that result from PIP 3 accumulation using liver Pten-deletion mice. To explore the role of AKT2, the major liver AKT isoform in steatosis induced by deletion of Pten, we created mice lacking both Pten and Akt2 in hepatocytes and compared the effect of deleting Akt2 and Pten in the double mutants to the Pten deletion mice alone. Hepatic lipid accumulation was significantly reduced in mice lacking both PTEN and AKT2, as compared with Pten mutant mice alone. This effect was due to the role of AKT2 in maintaining expression of genes involved in de novo lipogenesis. We showed that lipid accumulation in the double mutant hepatocytes was partially reversed by expression of constitutive active FOXO1, a transcription factor downstream of AKT not dependent on inhibition of atypical protein kinase C. In summary, this study delineated Lipid phosphatase and tensin homologue deleted on chromosome 10 (PTEN) functions to convert phosphotidylinositol-3,4,5-trisphosphate (PIP 3 ) to phosphatidylinositol bisphosphate.1 Thus, PTEN antagonizes the insulin-phosphoinositide 3-kindase (PI3K)/AKT pathway by reducing the levels of PIP 3 . In the liver, insulin activates PI3K signal to drive hepatic lipid accumulation. Mice lacking all PI3K activities are hypolipidemic and exhibit reduced expression of lipogenic genes in the liver.2 Previous studies reported a liver steatosis phenotype in mice when PTEN is lost in the hepatocytes. 3,4 In hepatocyte-specific Pten deletion mice, liver becomes a lipogenic organ, and accumulates triglyceride (TG) even though there is systemic hypoglycemia. 4 Both sterol regulatory element-binding proteins (SREBP-1c) and fatty acid synthase (FAS) are markedly elevated when PTEN is lost in the hepatocyte.3,4 This model, thus, is relevant to study how activation of the PI3K/AKT signaling pathway, specifically PIP 3 accumulation, induces lipogenesis.In this study, we considered the role of AKT2 in mediating the lipogenic effect of insulin/PI3K signaling. AKT2 is the major isoform of AKT that is expressed in the liver. AKT plays a pivotal role in hepatic insulin action.5 Adenovirus expression of constitutively activated AKT in vivo led to a similar fatty liver phenotype as loss of PTEN. 6 We hypothesized that AKT2 may mediate the metabolic phenotypes observed in the livers of Pten mutant animals. We investigated this hypothesis by crossing the hepatocytespecific Pten mutant mice 4 with the Akt2 Ϫ/Ϫ mice. 7 Our results indicate that loss of AKT2 can effectively block the fatty deposition in the liver of the Pten mutant mice. Our

Cancer stem cells (CSCs) are predicted to be critical drivers of tumor progression due to their "stemness", but the molecular mechanism of CSCs in regulating metastasis remains to be elucidated. Epithelial-mesenchymal transition (EMT), hypoxia-inducible factor (HIF)-1a, and miR-21, all of which contribute to cell migration for metastasis, are interrelated with CSCs. In the present study, third-sphere forming (3-S) CSC-like cells, which showed elevated CSC surface markers (ALDH1 + and CD44) and sphereforming capacity as well as migration and invasion capacities, were cultured and isolated from breast cancer MCF-7 parental cells, to evaluate the role of miR-21 in regulating the CSC-like cell biological features, especially EMT. EMT, which was assessed by overexpression of mesenchymal cell markers (N-cadherin, Vimentin, alpha-smooth muscle actin [a-SMA]) and suppression of epithelial cell marker (E-cadherin), was induced in 3-S CSC-like cells. Moreover, both of HIF-1a and miR-21 were upregulated in the CSC-like cells. Interestingly, antagonism of miR-21 by antagomir led to reversal of EMT, downexpression of HIF-1a, as well as suppression of invasion and migration, which indicates a key role of miR-21 involved in regulate CSC-associated features. In conclusion, we demonstrated that the formation of CSC-like cells undergoing process of EMT-like associated with overexpression of HIF-1a, both of which are regulated by miR-21. (Cancer Sci 2012; 103: 1058-1064 C ancer stem cells (CSCs) are predicted to be the cell origin of the tumor and responsible for tumor progression, relapse and metastasis due to their self-renewal capacity and limitless proliferative potential, as well as invasion and migration capacity.(1-5) Therefore, the development of successful cancer therapeutic regimen requires targeting the CSCs, such as the elucidation of molecular pathways, which regulate CSC features.Recently, breast cancer cells forming mammospheres in suspension cultures were generally acknowledged as breast cancer CSCs (bCSCs) due to their self-renewal capacity, (6,7) while mammospheres were also accepted as bCSC-like cell models, enriching bCSCs. Besides, bCSCs also could be identified and isolated according to cell surface markers such as aldehyde dehydrogenase 1 + (ALDH1 (1) But now, the isolation and culture of high-purity bCSC model is still one of the "choke points" in bCSC research.For most epithelial tumors, including breast cancer, progression toward malignancy is accompanied by a process of epithelial-mesenchymal transition (EMT), which is characterized by a loss of epithelial differentiation and a shift towards mesenchymal phenotype.(8) The EMT towards a more mesenchymal phenotype involves downexpression of epithelial markers (e.g. E-cadherin and Keratins) and upexpression of mesenchymal markers (e.g. N-cadherin, Vimentin, alphasmooth muscle actin [a-SMA]), as well as increased cell mobility and invasive phenotype.(9-11) Accumulating evidence demonstrated that the induction of EMT in vitro in transformed mammary epithelial...

Obesity confers an independent risk for carcinogenesis. In the liver, steatosis often proceeds cancer formation; however, the mechanisms by which steatosis promotes carcinogenesis is unknown. We hypothesize that steatosis alters the microenvironment to promote proliferation of tumor initiating cells (TICs) and carcinogenesis. We used several liver cancer models to address the mechanisms underlying the role of obesity in cancer and verified these findings in patient populations. Using bioinformatics analysis and verified by biochemical assays, we identified that hepatosteatosis resulting from either Pten deletion or transgenic expression of HCV core/NS5A proteins, promotes the activation of Wnt/β-catenin. We verified that high fat diet lipid accumulation is also capable of inducing Wnt/β-catenin. Caloric restriction inhibits hepatosteatosis, reduces Wnt/β-catenin activation and blocks the expansion of TICs leading to complete inhibition of tumorigenesis without affecting the phosphatase and tensin homologue deleted on chromosome 10 (PTEN) loss regulated protein kinase B (AKT) activation. Pharmacological inhibition or loss of the Wnt/β-catenin signal represses TIC growth in vitro, and decreases the accumulation of TICs in vivo. In human liver cancers, ontology analysis of gene set enrichment analysis (GSEA)-defined Wnt signature genes indicates that Wnt signaling is significantly induced in tumor samples compared with healthy livers. Indeed, Wnt signature genes predict 90% of tumors in a cohort of 558 patient samples. Selective depletion of macrophages leads to reduction of Wnt and suppresses tumor development, suggesting infiltrating macrophages as a key source for steatosis-induced Wnt expression. These data established Wnt/β-catenin as a novel signal produced by infiltrating macrophages induced by steatosis that promotes growth of tumor progenitor cells, underlying the increased risk of liver tumor development in obese individuals.