CD95 is part of a let-7/p53/miR-34 regulatory network

Fas (CD95) expression in adipocytes contributes to diet-induced obesity

OBJECTIVE

Induction of browning in white adipose tissue (WAT) increases energy expenditure and may be an attractive target for the treatment of obesity. Since activation of Fas (CD95) induces pathways known to blunt expression of uncoupling protein 1 (UCP1), we hypothesized that Fas expression in adipocytes inhibits WAT browning and thus contributes to the development of obesity.

METHODS

Adipocyte-specific Fas knockout (FasΔadipo) and control littermate (FasF/F) mice were fed a regular chow diet or a high-fat diet (HFD) for 20 weeks. Energy expenditure was assessed by indirect calorimetry, and browning was determined in subcutaneous WAT. In vitro, UCP1 was analyzed in subcutaneous murine adipocytes treated with or without Fas ligand. Moreover, FAS expression in WAT was correlated to UCP1 and percentage of body fat in human individuals.

RESULTS

HFD-fed FasΔadipo mice displayed reduced body weight gain and blunted adiposity compared to control littermates. Concomitantly, whole-body energy expenditure and WAT browning were elevated. In cultured adipocytes, Fas ligand treatment blunted isoproterenol-induced UCP1 protein levels. In support of these findings in rodents, FAS expression in WAT correlated negatively with UCP1 but positively with adiposity in human individuals.

CONCLUSIONS

Fas activation in adipocytes contributes to HFD-associated adiposity in rodents and may be a therapeutic target to reduce obesity and associated diseases.

Comprehensive miRNA and DNA Microarray Analyses Reveal the Response of Hepatic miR-203 and Its Target Gene to Protein Malnutrition in Rats

Adequate protein nutrition is essential for good health. Effects of protein malnutrition in animals have been widely studied at the mRNA level with the development of DNA microarray technology. Although microRNAs (miRNAs) have attracted attention for their function in regulating gene expression and have been studied in several disciplines, fewer studies have clarified the effects of protein malnutrition on miRNA alterations. The present study aimed to elucidate the relationship between protein malnutrition and miRNAs. Six-week old Wistar male rats were fed a control diet (20% casein) or a low-protein diet (5% casein) for two weeks, and their livers were subjected to both DNA microarray and miRNA array analysis. miR-203 was downregulated and its putative target Hadhb (hydroxyacyl-CoA dehydrogenase β subunit), known to regulate β-oxidation of fatty acids, was upregulated by the low-protein diet. In an in vitro experiment, miR-203 or its inhibitor were transfected in HepG2 cells, and the pattern of Hadhb expression was opposite to that of miR-203 expression. In addition, to clarifying the hepatic miRNA profile in response to protein malnutrition, these results showed that a low-protein diet increased Hadhb expression through downregulation of miR-203 and induced β-oxidation of fatty acids.

Repression of Irs2 by let-7 miRNAs is essential for homeostasis of the telencephalic neuroepithelium

Structural integrity and cellular homeostasis of the embryonic stem cell niche are critical for normal tissue development. In the telencephalic neuroepithelium, this is controlled in part by cell adhesion molecules and regulators of progenitor cell lineage, but the specific orchestration of these processes remains unknown. Here, we studied the role of microRNAs in the embryonic telencephalon as key regulators of gene expression. By using the early recombiner Rx-Cre mouse, we identify novel and critical roles of miRNAs in early brain development, demonstrating they are essential to preserve the cellular homeostasis and structural integrity of the telencephalic neuroepithelium. We show that Rx-Cre;Dicer^F/F mouse embryos have a severe disruption of the telencephalic apical junction belt, followed by invagination of the ventricular surface and formation of hyperproliferative rosettes. Transcriptome analyses and functional experiments in vivo show that these defects result from upregulation of Irs2 upon loss of let-7 miRNAs in an apoptosis-independent manner. Our results reveal an unprecedented relevance of miRNAs in early forebrain development, with potential mechanistic implications in pediatric brain cancer.

The Fas/FasL Signaling Pathway: Its Role in the Metastatic Process and as a Target for Treating Osteosarcoma Lung Metastases

Understanding how the tumor microenvironment participates in inhibiting or supporting tumor growth is critical for the development of novel therapies. Osteosarcoma (OS) metastasizes almost exclusively to the lung, an organ where Fas ligand (FasL) is constitutively expressed. This chapter focuses on our studies dedicated to the interaction of OS cells with the lung microenvironment. We will summarize our studies conducted over the past 20 years showing the importance of the Fas/FasL signaling pathway to the establishment and progression of OS metastases in the lung. We demonstrated that the FasL⁺ lung microenvironment eliminates Fas-positive (Fas⁺) OS cells that metastasize to the lungs, through apoptosis induced by Fas signaling following interaction of Fas on the tumor cell surface with FasL on the lung epithelial cells. Expression of the Fas receptor on OS cells inversely correlated with the ability of OS cells to form lung metastases. Blocking this pathway interferes with this process, allowing Fas⁺ cells to grow in the lung. By contrast, upregulation of Fas on Fas^- OS cells inhibited their ability to metastasize to the lung. We demonstrated how the FasL⁺ lung microenvironment can be leveraged for therapeutic intent through the upregulation of Fas expression. To this end, we demonstrated that the histone deacetylase inhibitor entinostat upregulated Fas expression on OS cells, reduced their ability to form lung metastases, and induced regression of established micrometastases. Fas expression in OS cells is regulated epigenetically by the microRNA miR-20a. We showed that expressions of Fas and miR-20a are inversely correlated, and that delivery of anti-miR-20a in vivo to mice with established osteosarcoma lung metastases resulted in upregulation of Fas and tumor regression. Therefore, targeting the Fas signaling pathway may present therapeutic opportunities, which target the lung microenvironment for elimination of OS lung metastases. We have also shown that in addition to being critically involved in the metastatic potential, the Fas signaling pathway may also contribute to the efficacy of chemotherapy. We demonstrated that the chemotherapeutic agent gemcitabine (GCB) increased Fas expression in both human and mouse OS cells in vitro. In vivo, aerosol GCB therapy induced upregulation of Fas expression and the regression of established osteosarcoma lung metastases. The therapeutic efficacy of GCB was contingent upon a FasL⁺ lung microenvironment as aerosol GCB had no effect in FasL-deficient mice. Manipulation of Fas expression and the Fas pathway should be considered, as this concept may provide additional novel therapeutic approaches for treating patients with OS lung metastases.

MicroRNAs in cancer cell death pathways: Apoptosis and necroptosis

To protect tissues and the organism from disease, potentially harmful cells are removed through programmed cell death processes, including apoptosis and necroptosis. These types of cell death are critically controlled by microRNAs (miRNAs). MiRNAs are short RNA molecules that target and inhibit expression of many cellular regulators, including those controlling programmed cell death via the intrinsic (Bcl-2 and Mcl-1), extrinsic (TRAIL and Fas), p53-and endoplasmic reticulum (ER) stress-induced apoptotic pathways, as well as the necroptosis cell death pathway. In this review, we discuss the current knowledge of apoptosis and necroptosis pathways and how these are impaired in cancer cells. We focus on how miRNAs disrupt apoptosis and necroptosis, thereby critically contributing to malignancy. Understanding which and how miRNAs and their targets affect cell death pathways could open up novel therapeutic opportunities for cancer patients. Indeed, restoration of pro-apoptotic tumor suppressor miRNAs (apoptomiRs) or inhibition of oncogenic miRNAs (oncomiRs) represent strategies that are currently being trialed or are already applied as miRNA-based cancer therapies. Therefore, better understanding the cancer type-specific expression of apoptomiRs and oncomiRs and their underlying mechanisms in cell death pathways will not only advance our knowledge, but also continue to provide new opportunities to treat cancer.

Multidimensional profiling of drug-treated cells by Imaging Mass Cytometry

In pharmaceutical research, high‐content screening is an integral part of lead candidate development. Measuring drug response in vitro by examining over 40 parameters, including biomarkers, signaling molecules, cell morphological changes, proliferation indices, and toxicity in a single sample, could significantly enhance discovery of new therapeutics. As a proof of concept, we present here a workflow for multidimensional Imaging Mass Cytometry™ (IMC™) and data processing with open source computational tools. CellProfiler was used to identify single cells through establishing cellular boundaries, followed by histoCAT™ (histology topography cytometry analysis toolbox) for extracting single‐cell quantitative information visualized as t‐SNE plots and heatmaps. Human breast cancer‐derived cell lines SKBR3, HCC1143, and MCF‐7 were screened for expression of cellular markers to generate digital images with a resolution comparable to conventional fluorescence microscopy. Predicted pharmacodynamic effects were measured in MCF‐7 cells dosed with three target‐specific compounds: growth stimulatory EGF, microtubule depolymerization agent nocodazole, and genotoxic chemotherapeutic drug etoposide. We show strong pairwise correlation between nuclear markers pHistone3^S28, Ki‐67, and p4E‐BP1^T37/T46 in classified mitotic cells and anticorrelation with cell surface markers. Our study demonstrates that IMC data expand the number of measured parameters in single cells and brings higher‐dimension analysis to the field of cell‐based screening in early lead compound discovery.

CD95/Fas and metastatic disease: What does not kill you makes you stronger

CD95 (also known as Fas) is the prototype of death receptors; however, evidence suggests that this receptor mainly implements non-apoptotic signaling pathways such as NF-κB, MAPK, and PI3K that are involved in cell migration, differentiation, survival, and cytokine secretion. At least two different forms of CD95 L exist. The multi-aggregated transmembrane ligand (m-CD95 L) is cleaved by metalloproteases to release a homotrimeric soluble ligand (s-CD95 L). Unlike m-CD95 L, the interaction between s-CD95 L and its receptor CD95 fails to trigger apoptosis, but instead promotes calcium-dependent cell migration, which contributes to the accumulation of inflammatory Th17 cells in damaged organs of lupus patients and favors cancer cell invasiveness. Novel inhibitors targeting the pro-inflammatory roles of CD95/CD95 L may provide attractive therapeutic options for patients with chronic inflammatory disorders or cancer. This review discusses the roles of the CD95/CD95 L pair in cell migration and metastasis.

Expression profile of Let-7s in peripheral blood mononuclear cells of normal and severe preeclampsia pregnant women

HEADINGS AIM

We aimed to investigate if the let-7 s expression level in the serum of peripheral blood from pregnant women with severe pre-eclampsia and normal pregnant women is related to the incidence of severe pre-eclampsia.

METHODS

Total RNA was extracted from collected peripheral blood mononuclear cells from 20 or over weeks pregnant women diagnosed with severe pre-eclampsia (age: 31.57 ± 4.94) and normal pregnant women (age: 29.75 ± 4.6) respectively, followed by real-time PCR to examine the expression of let-7 s. Correlation between let-7 s expression level and maternal age or body mass index of the normal pregnant women were also analyzed using SPSS21.0 software.

RESULTS

Let-7a and let-7 g were significantly increased in pregnant women with severe pre-eclampsia by 4.67 fold and 2.37 fold respectively compared to the normal pregnant women, whereas there was no significant difference in let-7b and let-7i. Moreover, there was no correlation between maternal age or body mass index and the expression level of let-7a, let-7b, let-7 g, and let-7i.

CONCLUSIONS

In conclusion, let-7a and let-7 g were significantly increased in the PBMCs of severe pre-eclampsia women compared to normal controls. Moreover, their expression level was not correlated to the maternal age or body mass of patients. Our data indicated that let-7a and let-7 g may be considered as predictive markers for SPE.

Survival of Naïve T Cells Requires the Expression of Let-7 miRNAs

Maintaining the diversity and constant numbers of naïve T cells throughout the organism's lifetime is necessary for efficient immune responses. Naïve T cell homeostasis, which consists of prolonged survival, occasional proliferation and enforcement of quiescence, is tightly regulated by multiple signaling pathways which are in turn controlled by various transcription factors. However, full understanding of the molecular mechanisms underlying the maintenance of the peripheral T cell pool has not been achieved. In the present study, we demonstrate that T cell-specific deficiency in let-7 miRNAs results in peripheral T cell lymphopenia resembling that of Dicer1 knockout mice. Deletion of let-7 leads to profound T cell apoptosis while overexpression prevents it. We further show that in the absence of let-7, T cells cannot sustain optimal levels of the pro-survival factor Bcl2 in spite of the intact IL-7 signaling, and re-expression of Bcl2 in let-7 deficient T cells completely rescues the survival defect. Thus, we have uncovered a novel let-7-dependent mechanism of post-transcriptional regulation of naïve T cell survival in vivo.

MicroRNA-34 family in breast cancer: from research to therapeutic potential

MicroRNA (miRNA)-34 family (miR-34s), including miR-34a/b/c, is the most well studied non-coding RNAs that regulate gene expression post-transcriptionally. The miR-34s mediates the tumor suppressor function of p53 in the pathogenesis of breast cancer by targeting different oncogenes. This review focuses on the anti-oncogenic regulation of the miR-34s, emphasizing the major signaling pathways that are involved in the modulation of miR-34s in breast cancer. Moreover, it highlights how epigenetic modification by the p53/miR-34s axis regulates the proliferation, invasiveness, chemoresistance, and sternness of breast cancer. A better understanding of the molecular mechanisms of miR-34s will open new opportunities for the development of novel therapeutic strategies and define a new approach in identifying potential biomarkers for early diagnosis of breast cancer.

Bioinformatics functional analysis of let-7a, miR-34a, and miR-199a/b reveals novel insights into immune system pathways and cancer hallmarks for hepatocellular carcinoma

Let-7a, miR-34a, and miR-199 a/b have gained a great attention as master regulators for cellular processes. In particular, these three micro-RNAs act as potential onco-suppressors for hepatocellular carcinoma. Bioinformatics can reveal the functionality of these micro-RNAs through target prediction and functional annotation analysis. In the current study, in silico analysis using innovative servers (miRror Suite, DAVID, miRGator V3.0, GeneTrail) has demonstrated the combinatorial and the individual target genes of these micro-RNAs and further explored their roles in hepatocellular carcinoma progression. There were 87 common target messenger RNAs (p ≤ 0.05) that were predicted to be regulated by the three micro-RNAs using miRror 2.0 target prediction tool. In addition, the functional enrichment analysis of these targets that was performed by DAVID functional annotation and REACTOME tools revealed two major immune-related pathways, eight hepatocellular carcinoma hallmarks-linked pathways, and two pathways that mediate interconnected processes between immune system and hepatocellular carcinoma hallmarks. Moreover, protein-protein interaction network for the predicted common targets was obtained by using STRING database. The individual analysis of target genes and pathways for the three micro-RNAs of interest using miRGator V3.0 and GeneTrail servers revealed some novel predicted target oncogenes such as SOX4, which we validated experimentally, in addition to some regulated pathways of immune system and hepatocarcinogenesis such as insulin signaling pathway and adipocytokine signaling pathway. In general, our results demonstrate that let-7a, miR-34a, and miR-199 a/b have novel interactions in different immune system pathways and major hepatocellular carcinoma hallmarks. Thus, our findings shed more light on the roles of these miRNAs as cancer silencers.

miR-20a Regulates FAS Expression in Osteosarcoma Cells by Modulating FAS Promoter Activity and Can be Therapeutically Targeted to Inhibit Lung Metastases

The metastatic potential of osteosarcoma cells is inversely correlated to cell surface FAS expression. Downregulation of FAS allows osteosarcoma cells to escape FAS ligand-mediated apoptosis when they enter a FAS ligand-positive microenvironment such as the lung. We have previously demonstrated that miR-20a, encoded by the miR-17-92 cluster, downregulates FAS expression in osteosarcoma. We further demonstrated an inverse correlation between FAS expression and miR-20a expression. However, the mechanism of FAS regulation by miR-20a was still unclear. The purpose of the current study was to evaluate the mechanism of FAS regulation by miR-20a in vitro and test the effect of targeting miR-20a in vivo We investigated whether miR-20a's downregulation of FAS was mediated by binding to the 3'-untranslated region (3'-UTR) of FAS mRNA with the consequent induction of mRNA degradation or translational suppression. We identified and mutated two miR-20a binding sites on the FAS mRNA 3'-UTR. Using luciferase reporter assays, we demonstrated that miR-20a did not bind to either the wild-type or mutated FAS 3'-UTR. In contrast, overexpression of miR-20a resulted in downregulation of FAS promoter activity. Similarly, the inhibition of miR-20a increased FAS promoter activity. The critical region identified on the FAS promoter was between -240 bp and -150 bp. Delivery of anti-miR-20a in vivo using nanoparticles in mice with established osteosarcoma lung metastases resulted in upregulation of FAS and tumor growth inhibition. Taken together, our data suggest that miR-20a regulates FAS expression through the modulation of the FAS promoter and that targeting miR-20a using anti-miR-20a has therapeutic potential. Mol Cancer Ther; 17(1); 130-9. ©2017 AACR.

The Hepatoprotective and MicroRNAs Downregulatory Effects of Crocin Following Hepatic Ischemia-Reperfusion Injury in Rats

Background. Liver ischemia-reperfusion (IR) injury is one of the chief etiologies of tissue damage during liver transplantation, hypovolemic shock, and so forth. This study aimed to evaluate hepatoprotective effect of crocin on IR injury and on microRNAs (miR-122 and miR-34a) expression. Materials and Methods. 32 rats were randomly divided into four groups: sham, IR, crocin pretreatment (Cr), and crocin pretreatment + IR (Cr + IR) groups. In sham and Cr groups, animals were given normal saline (N/S) and Cr (200 mg/Kg) for 7 consecutive days, respectively, and laparotomy without inducing IR was done. In IR and Cr + IR groups, N/S and Cr were given for 7 consecutive days and rats underwent a partial (70%) ischemia for 45 min/reperfusion for 60 min. Blood and tissue samples were taken for biochemical, molecular, and histopathological examinations. Results. The results showed decreased levels of antioxidants activity and increased levels of liver enzymes improved by crocin. The expression of miR-122, miR-34a, and p53 decreased, while Nrf2 increased by crocin. Crocin ameliorated histopathological changes. Conclusion. The results demonstrated that crocin protected the liver against IR injury through increasing the activity of antioxidant enzymes, improving serum levels of liver enzymes, downregulating miR-122, miR-34a, and p53, and upregulating Nrf2 expression.

microRNA regulators of apoptosis in cancer

This brief review summarizes our current knowledge on the microRNAs that regulate apoptosis machinery and are potentially involved in the dysregulation or deregulation of apoptosis, a well known hallmark of cancer. microRNAs are critical regulators of the most important cellular processes, including apoptosis. Expression of microRNAs is found to be dysregulated in many malignancies, leading to apoptosis inhibition in cancer, or resistance to current therapies. To date, there are over 80 microRNAs directly involved in apoptosis regulation or dysregulation that can impact cancer detection, initiation, progression, invasion, metastasis or resistance to anti-cancer therapy. Development of microRNA-based therapeutic strategies is now taking shape in the clinic. Thus, these microRNAs represent potential targets or tools for cancer therapy in the future.

The tumor-suppressive and potential therapeutic functions of miR-34a in epithelial carcinomas

INTRODUCTION

Many RNA species have been identified as important players in the development of chronic diseases including cancer. Certain classes of regulatory RNAs such as microRNAs (miRNAs) have been investigated in such detail that bona fide tumor suppressive and oncogenic miRNAs have been identified. Because of this, there has been a major effort to therapeutically target these small RNAs. One in particular, a liposomal formulation of miR-34a (MRX34), has entered Phase I trials.

AREAS COVERED

This review aims to summarize miRNA biology, its regulation within normal versus disease states and how it can be targeted therapeutically, with a particular emphasis on miR-34a. Understanding the complexity of a single miRNA will aid in the development of future RNA-based therapeutics for a broader range of chronic diseases.

EXPERT OPINION

The potential of miRNAs to be developed into anti-cancer therapeutics has become an increasingly important area of research. miR-34a is a tumor suppressive miRNA across many tumor types through its ability to inhibit cellular proliferation, invasion and tumor sphere formation. miR-34a also shows promise within certain in vivo solid tumor models. Finally, as miR-34a moves into clinical trials it will be important to determine if it can further sensitize tumors to certain chemotherapeutic agents.

Primary analysis and screening of microRNAs in gastric cancer side population cells

AIM: To explore the microRNA (miRNA) profiles and to determine the key miRNAs within the side population (SP) cells of the gastric cancer cell line MKN-45.

METHODS: We used fluorescence-activated cell sorting and Hoechst 33342 labeling to obtain SP cells from the human gastric carcinoma cell line MKN-45. The miRNA expression profiles of the SP and major population (MP) cells were examined using a miRNA gene chip, and key miRNAs were obtained according to aberrant expression and the miRNAs’ possible targets as predicted by bioinformatics.

RESULTS: Using a significance criterion of a 1.5-fold or greater difference in expression level, we observed an increase in the expression of 34 miRNAs and a decrease in the expression of 34 miRNAs when comparing SP to MP cells. Using quantitative real-time reverse transcription-polymerase chain reaction to test for differentially expressed miRNAs combined with bioinformatics results, we found that the downregulated miRNAs, such as hsa-miR-3175 and hsa-miR-203, and the upregulated miRNAs, including hsa-miR-130a, hsa-miR-324-5p, hsa-miR-34a, and hsa-miR-25-star, may be important in maintaining and regulating the characteristics of SP cells.

CONCLUSION: There are key miRNAs expressed within the SP cells of the gastric cancer cell line MKN-45, and include hsa-miR-3175, hsa-miR-203, hsa-miR-130a, hsa-miR-324-5p, hsa-miR-34a, and hsa-miR-25-star.

miRs-138 and -424 control palmitoylation-dependent CD95-mediated cell death by targeting acyl protein thioesterases 1 and 2 in CLL

Resistance toward CD95-mediated apoptosis is a hallmark of many different malignancies, as it is known from primary chronic lymphocytic leukemia (CLL) cells. Previously, we could show that miR-138 and -424 are downregulated in CLL cells. Here, we identified 2 new target genes, namely acyl protein thioesterase (APT) 1 and 2, which are under control of both miRs and thereby significantly overexpressed in CLL cells. APTs are the only enzymes known to promote depalmitoylation. Indeed, membrane proteins are significantly less palmitoylated in CLL cells compared with normal B cells. We identified APTs to directly interact with CD95 to promote depalmitoylation, thus impairing apoptosis mediated through CD95. Specific inhibition of APTs by siRNAs, treatment with miRs-138/-424, and pharmacologic approaches restore CD95-mediated apoptosis in CLL cells and other cancer cells, pointing to an important regulatory role of APTs in CD95 apoptosis. The identification of the depalmitoylation reaction of CD95 by APTs as a microRNA (miRNA) target provides a novel molecular mechanism for how malignant cells escape from CD95-mediated apoptosis. Here, we introduce palmitoylation as a novel posttranslational modification in CLL, which might impact on localization, mobility, and function of molecules, survival signaling, and migration.

The role of CD95 and CD95 ligand in cancer

CD95 (Fas/APO-1) and its ligand, CD95L, have long been viewed as a death receptor/death ligand system that mediates apoptosis induction to maintain immune homeostasis. In addition, these molecules are important in the immune elimination of virus-infected cells and cancer cells. CD95L was, therefore, considered to be useful for cancer therapy. However, major side effects have precluded its systemic use. During the last 10 years, it has been recognized that CD95 and CD95L have multiple cancer-relevant nonapoptotic and tumor-promoting activities. CD95 and CD95L were discovered to be critical survival factors for cancer cells, and were found to protect and promote cancer stem cells. We now discuss five different ways in which inhibiting or eliminating CD95L, rather than augmenting, may be beneficial for cancer therapy alone or in combination with standard chemotherapy or immune therapy.

Ovarian Cancer HO-8910 Cell Apoptosis Induced by Crocin in vitro

The effect and mechanism of ovarian cancer HO-8910 cell apoptosis induced by crocin. MTT assay was performed to detect the inhibitory action of crocin on the proliferation of HO-8910 cells. Flow cytometry was used to test the cell cycle distribution and apoptosis rate of ovarian cancer HO-8910 cells. Western blot analysis was utilized to measure the levels of apoptotic proteins such as p53, Fas/APO-1, and Caspase-3. MTT analysis revealed that crocin significantly inhibited the growth of HO-8910 cells. Additionally, flow cytometry illustrated that crocin raised the proportion of HO-8910 cells in the G0/G1 phase and increased their apoptosis rate. Furthermore, Western blot analysis revealed that crocin up-regulated the expression of p53, Fas/APO-1, and Caspase-3. The results of this study showed that crocin can significantly inhibit the growth of HO-8910 cells and arrest them in the G0/G1 phase. Crocin can also promote ovarian cancer HO-8910 cell apoptosis, most likely by increasing p53 and Fas/APO-1 expression, and then activating the apoptotic pathway regulated by Caspase-3.

CD95 and CD95L promote and protect cancer stem cells

CD95 (APO-1/Fas) is a death receptor used by immune cells to kill cancer cells through induction of apoptosis. However, the elimination of CD95 or its ligand, CD95L, from cancer cells results in death induced by CD95R/L elimination (DICE), a type of cell death that resembles a necrotic form of mitotic catastrophe suggesting that CD95 protects cancer cells from cell death. We now report that stimulation of CD95 on cancer cells or reducing miR-200c levels increases the number of cancer stem cells (CSCs), which are more sensitive to induction of DICE than non-CSC, while becoming less sensitive to CD95-mediated apoptosis. In contrast, induction of DICE or overexpression of miR-200c reduces the number of CSCs. We demonstrate that CSCs and non-CSCs have differential sensitivities to CD95-mediated apoptosis and DICE, and that killing of cancer cells can be maximized by concomitant induction of both cell death mechanisms.

Mir-34: a new weapon against cancer?

The microRNA(miRNA)-34a is a key regulator of tumor suppression. It controls the expression of a plethora of target proteins involved in cell cycle, differentiation and apoptosis, and antagonizes processes that are necessary for basic cancer cell viability as well as cancer stemness, metastasis, and chemoresistance. In this review, we focus on the molecular mechanisms of miR-34a-mediated tumor suppression, giving emphasis on the main miR-34a targets, as well as on the principal regulators involved in the modulation of this miRNA. Moreover, we shed light on the miR-34a role in modulating responsiveness to chemotherapy and on the phytonutrients-mediated regulation of miR-34a expression and activity in cancer cells. Given the broad anti-oncogenic activity of miR-34a, we also discuss the substantial benefits of a new therapeutic concept based on nanotechnology delivery of miRNA mimics. In fact, the replacement of oncosuppressor miRNAs provides an effective strategy against tumor heterogeneity and the selective RNA-based delivery systems seems to be an excellent platform for a safe and effective targeting of the tumor.

FAS-based cell depletion facilitates the selective isolation of mouse induced pluripotent stem cells

Cellular reprogramming of somatic cells into induced pluripotent stem cells (iPSC) opens up new avenues for basic research and regenerative medicine. However, the low efficiency of the procedure remains a major limitation. To identify iPSC, many studies to date relied on the activation of pluripotency-associated transcription factors. Such strategies are either retrospective or depend on genetically modified reporter cells. We aimed at identifying naturally occurring surface proteins in a systematic approach, focusing on antibody-targeted markers to enable live-cell identification and selective isolation. We tested 170 antibodies for differential expression between mouse embryonic fibroblasts (MEF) and mouse pluripotent stem cells (PSC). Differentially expressed markers were evaluated for their ability to identify and isolate iPSC in reprogramming cultures. Epithelial cell adhesion molecule (EPCAM) and stage-specific embryonic antigen 1 (SSEA1) were upregulated early during reprogramming and enabled enrichment of OCT4 expressing cells by magnetic cell sorting. Downregulation of somatic marker FAS was equally suitable to enrich OCT4 expressing cells, which has not been described so far. Furthermore, FAS downregulation correlated with viral transgene silencing. Finally, using the marker SSEA-1 we exemplified that magnetic separation enables the establishment of bona fide iPSC and propose strategies to enrich iPSC from a variety of human source tissues.

c-Jun N-terminal kinase 1/c-Jun activation of the p53/microRNA 34a/sirtuin 1 pathway contributes to apoptosis induced by deoxycholic acid in rat liver

MicroRNAs (miRs) are increasingly associated with metabolic liver diseases. We have shown that ursodeoxycholic acid, a hydrophilic bile acid, counteracts the miR-34a/sirtuin 1 (SIRT1)/p53 pathway, activated in the liver of nonalcoholic steatohepatitis (NASH) patients. In contrast, hydrophobic bile acids, particularly deoxycholic acid (DCA), activate apoptosis and are increased in NASH. We evaluated whether DCA-induced apoptosis of rat hepatocytes occurs via miR-34a-dependent pathways and whether they connect with c-Jun N-terminal kinase (JNK) induction. DCA enhanced miR-34a/SIRT1/p53 proapoptotic signaling in a dose- and time-dependent manner. In turn, miR-34a inhibition and SIRT1 overexpression significantly rescued targeting of the miR-34a pathway and apoptosis by DCA. In addition, p53 overexpression activated the miR-34a/SIRT1/p53 pathway, further induced by DCA. DCA increased p53 expression as well as p53 transcriptional activation of PUMA and miR-34a itself, providing a functional mechanism for miR-34a activation. JNK1 and c-Jun were shown to be major targets of DCA, upstream of p53, in engaging the miR-34a pathway and apoptosis. Finally, activation of this JNK1/miR-34a proapoptotic circuit was also shown to occur in vivo in the rat liver. These results suggest that the JNK1/p53/miR-34a/SIRT1 pathway may represent an attractive pharmacological target for the development of new drugs to arrest metabolism- and apoptosis-related liver pathologies.