Diet suppresses glioblastoma initiation in mice by maintaining quiescence of mutation-bearing neural stem cells.

Glioblastoma is thought to originate from neural stem cells (NSCs) of the subventricular zone that acquire genetic alterations. In the adult brain, NSCs are largely quiescent, suggesting that deregulation of quiescence maintenance may be a prerequisite for tumor initiation. Although inactivation of the tumor suppressor p53 is a frequent event in gliomagenesis, whether or how it affects quiescent NSCs (qNSCs) remains unclear. Here, we show that p53 maintains quiescence by inducing fatty-acid oxidation (FAO) and that acute p53 deletion in qNSCs results in their premature activation to a proliferative state. Mechanistically, this occurs through direct transcriptional induction of PPARGC1a, which in turn activates PPARα to upregulate FAO genes. Dietary supplementation with fish oil containing omega-3 fatty acids, natural PPARα ligands, fully restores quiescence of p53-deficient NSCs and delays tumor initiation in a glioblastoma mouse model. Thus, diet can silence glioblastoma driver mutations, with important implications for cancer prevention.

A PML/Slit Axis Controls Physiological Cell Migration and Cancer Invasion in the CNS.

Cell migration through the brain parenchyma underpins neurogenesis and glioblastoma (GBM) development. Since GBM cells and neuroblasts use the same migratory routes, mechanisms underlying migration during neurogenesis and brain cancer pathogenesis may be similar. Here, we identify a common pathway controlling cell migration in normal and neoplastic cells in the CNS. The nuclear scaffold protein promyelocytic leukemia (PML), a regulator of forebrain development, promotes neural progenitor/stem cell (NPC) and neuroblast migration in the adult mouse brain. The PML pro-migratory role is active also in transformed mouse NPCs and in human primary GBM cells. In both normal and neoplastic settings, PML controls cell migration via Polycomb repressive complex 2 (PRC2)-mediated repression of Slits, key regulators of axon guidance. Finally, a PML/SLIT1 axis regulates sensitivity to the PML-targeting drug arsenic trioxide in primary GBM cells. Taken together, these findings uncover a drug-targetable molecular axis controlling cell migration in both normal and neoplastic cells.

Potential Role of ANGPTL4 in the Cross Talk between Metabolism and Cancer through PPAR Signaling Pathway.

The angiopoietin-like 4 (ANGPTL4) protein belongs to a superfamily of secreted proteins structurally related to factors modulating angiogenesis known as angiopoietins. At first, ANGPTL4 has been identified as an adipokine exclusively involved in lipid metabolism, because of its prevalent expression in liver and adipose tissue. This protein regulates lipid metabolism by inhibiting lipoprotein lipase (LPL) activity and stimulating lipolysis of white adipose tissue (WAT), resulting in increased levels of plasma triglycerides (TG) and fatty acids. Subsequently, ANGPTL4 has been shown to be involved in several nonmetabolic and metabolic conditions, both physiological and pathological, including angiogenesis and vascular permeability, cell differentiation, tumorigenesis, glucose homoeostasis, lipid metabolism, energy homeostasis, wound healing, inflammation, and redox regulation. The transcriptional regulation of ANGPTL4 can be modulated by several transcription factors, including PPARα, PPARß/δ, PPARγ, and HIF-1α, and nutritional and hormonal conditions. Several studies showed that high levels of ANGPTL4 are associated with poor prognosis in patients with various solid tumors, suggesting an important role in cancer onset and progression, metastasis, and anoikis resistance. Here, we have discussed the potential role of ANGPTL4 in mediating the cross talk between metabolic syndromes, such as diabetes and obesity, and cancer through regulation of its expression by PPARs.

Can the microRNA expression profile help to identify novel targets for zoledronic acid in breast cancer?

Zoledronic acid (ZOL), belonging to third generation bisphosphonate family, is a potent inhibitor of osteoclast-mediated bone resorption, widely used to effectively prevent osteolysis in breast cancer patients who develop bone metastases. Low doses of ZOL have been shown to exhibit a direct anticancer role, by inhibiting cell adhesion, invasion, cytoskeleton remodelling and proliferation in MCF-7 breast cancer cells. In order to identify the molecular mechanisms and signaling pathways underlying the anticancer activity exerted by ZOL, we analyzed for the first time the microRNA expression profile in breast cancer cells. A large-scale microarray analysis of 377 miRNAs was performed on MCF7 cells treated with 10 µM ZOL for 24 h compared to untreated cells. Furthermore, the expression of specific ZOL-induced miRNAs was analyzed in MCF-7 and SkBr3 cells through Real-time PCR. Low-dose treatment with ZOL significantly altered expression of 54 miRNAs. Nine upregulated and twelve downregulated miRNAs have been identified after 24 h of treatment. Also, ZOL induced expression of 11 specific miRNAs and silenced expression of 22 miRNAs. MiRNA data analysis revealed the involvement of differentially expressed miRNAs in PI3K/Akt, MAPK, Wnt, TGF-ß, Jak-STAT and mTOR signaling pathways, and regulation of actin cytoskeleton. Our results have been shown to be perfectly coherent with the recent findings reported in literature concerning changes in expression of some miRNAs involved in bone metastasis formation, progression, therapy resistance in breast cancer. In conclusion, this data supports the hypothesis that ZOL-induced modification of the miRNA expression profile contributes to the anticancer efficacy of this agent.

Exosomal shuttling of miR-126 in endothelial cells modulates adhesive and migratory abilities of chronic myelogenous leukemia cells.

BACKGROUND: Recent findings indicate that exosomes released from cancer cells contain microRNAs (miRNAs) that may be delivered to cells of tumor microenvironment. RESULTS: To elucidate whether miRNAs secreted from chronic myelogenous leukemia cells (CML) are shuttled into endothelial cells thus affecting their phenotype, we first analysed miRNAs content in LAMA84 exosomes. Among the 124 miRNAs identified in LAMA84 exosomes, we focused our attention on miR-126 which was found to be over-overexpressed in exosomes compared with producing parental cells. Transfection of LAMA84 with Cy3-labelled miR-126 and co-culture of leukemia cells with endothelial cells (EC) confirmed that miR-126 is shuttled into HUVECs. The treatment of HUVECs with LAMA84 exosomes for 24 hours reduced CXCL12 and VCAM1 expression, both at the mRNA and protein level, and negatively modulated LAMA84 motility and cells adhesion. Transfection in HUVECs of miR-126 inhibitor reversed the decrease of CXCL12 and restored the motility and adhesion of LAMA84 cells while the over-expression of miR-126, showed opposite effects. CONCLUSION: Our results show that the miR-126 shuttled by exosomes is biologically active in the target cells, and support the hypothesis that exosomal miRNAs have an important role in tumor-endothelial crosstalk occurring in the bone marrow microenvironment, potentially affecting disease progression.

Circulating miR-22, miR-24 and miR-34a as novel predictive biomarkers to pemetrexed-based chemotherapy in advanced non-small cell lung cancer.

Pemetrexed has been widely used in patients with advanced non-small cell lung cancer (NSCLC). The clinical relevance of polymorphisms of folate pathway genes for pemetrexed metabolism have not been fully elucidated yet. The aim of this study was to evaluate the expression levels of circulating miR-22, miR-24, and miR-34a, possibly involved in folate pathway, in NSCLC patients treated with pemetrexed compared with healthy controls and to investigate their impact on patient clinical outcomes. A total of 22 consecutive patients with advanced NSCLC, treated with pemetrexed-based chemotherapy and 27 age and sex matched healthy controls were included in this preliminary analysis. miR-22, miR-24, and miR-34a targets were identified by TargetScan 6.2 algorithm, validating the involvement of these microRNAs in folate pathway. MicroRNAs were isolated from whole blood and extracted with miRNAeasy Mini Kit (Qiagen). miRNA profiling was performed using Real-Time PCR. SPSS 17 was used to data analysis. miR-22, miR-24, and miR-34a were found upregulated (P<0.05) in NSCLC patients versus healthy controls. Higher expression levels were recorded for miR-34a. Nevertheless, significantly higher miR-22 expression was observed in patients developing progressive disease (P=0.03). No significant associations with clinical outcome were recorded for miR-24 and miR-34a. Albeit preliminary, these data support the involvement of miR-22, miR-24, and miR-34a in advanced NSCLC. The correlation between high expression of miR-22 in whole blood and the lack of response in pemetrexed treated NSCLC patients indicates that miR-22 could represent a novel predictive biomarker for pemetrexed-based treatment.

Effects of anti-miR-182 on TSP-1 expression in human colon cancer cells: there is a sense in antisense?

OBJECTIVE: miRNAs are attractive molecules for cancer treatment, including colon rectal cancer (CRC). We investigate on the molecular mechanism by which miR-182 could regulate thrombospondin-1 (TSP-1) expression, a protein downregulated in CRC and inversely correlated with tumor vascularity and metastasis. BACKGROUND: MicroRNAs are small non-coding RNAs that regulate the expression of different genes, involved in cancer progression, angiogenesis and metastasis. miR-182, over-expressed in colorectal cancer (CRC), has like predictive target thrombospondin-1 (TSP-1), a protein inversely correlated with tumor vascularity and metastasis that results downregulated in different types of cancer including CRC. RESULTS: We found that TSP-1 increased after transfection with anti-miR-182 and we showed that miR-182 targets TSP-1 3'UTR-mRNA in both cells. Moreover, we observed that anti-miR-182 did not induce significant variation of Egr-1 expression, but affected the nuclear translocation and its binding on tsp-1 promoter in HCT-116. Equally, Sp-1 was slightly increased as total protein, rather we found a nuclear accumulation and its loading on the TSP-1 promoter in HT-29 transfected with anti-miR-182. CONCLUSION: Our data suggest that miR-182 targets the anti-angiogenic factor TSP-1 and that anti-miR-182 determines an upregulation of TSP-1 expression in colon cancer cells. Moreover, anti-miR-182 exerts a transcriptional regulatory mechanism of tsp-1 modulating Egr-1 and Sp-1 function. Anti-miR-182 could be used to restore TSP-1 expression in order to contrast angiogenic and invasive events in CRC.

Genetic and molecular characterization of the human osteosarcoma 3AB-OS cancer stem cell line: a possible model for studying osteosarcoma origin and stemness.

Finding new treatments targeting cancer stem cells (CSCs) within a tumor seems to be critical to halt cancer and improve patient survival. Osteosarcoma is an aggressive tumor affecting adolescents, for which there is no second-line chemotherapy. Uncovering new molecular mechanisms underlying the development of osteosarcoma and origin of CSCs is crucial to identify new possible therapeutic strategies. Here, we aimed to characterize genetically and molecularly the human osteosarcoma 3AB-OS CSC line, previously selected from MG63 cells and which proved to have both in vitro and in vivo features of CSCs. Classic cytogenetic studies demonstrated that 3AB-OS cells have hypertriploid karyotype with 71-82 chromosomes. By comparing 3AB-OS CSCs to the parental cells, array CGH, Affymetrix microarray, and TaqMan® Human MicroRNA array analyses identified 49 copy number variations (CNV), 3,512 dysregulated genes and 189 differentially expressed miRNAs. Some of the chromosomal abnormalities and mRNA/miRNA expression profiles appeared to be congruent with those reported in human osteosarcomas. Bioinformatic analyses selected 196 genes and 46 anticorrelated miRNAs involved in carcinogenesis and stemness. For the first time, a predictive network is also described for two miRNA family (let-7/98 and miR-29a,b,c) and their anticorrelated mRNAs (MSTN, CCND2, Lin28B, MEST, HMGA2, and GHR), which may represent new biomarkers for osteosarcoma and may pave the way for the identification of new potential therapeutic targets.

Effects of PPARγ agonists on the expression of leptin and vascular endothelial growth factor in breast cancer cells.

The obesity hormone leptin has been implicated in breast cancer development. Breast cancer cells express the leptin receptor and are able to synthesize leptin in response to obesity-related stimuli. Furthermore, leptin is a positive regulator of vascular endothelial growth factor (VEGF) and high levels of both proteins are associated with worse prognosis in breast cancer patients. Peroxisome proliferator-activated receptor γ (PPARγ) ligands are therapeutic agents used in patient with Type 2 diabetes and obesity which have recently been studied for their potential anti-tumor effect. Here, we studied if these compounds, ciglitazone and GW1929, can affect the expression of leptin and VEGF in breast cancer cells. In MDA-MB-231 and MCF-7 breast cancer cells, treatment with submolar concentrations of ciglitazone and GW1929 elevated the expression of leptin and VEGF mRNA and protein, and increased cell viability and migration. These effects coincided with increased recruitment of PPARγ to the proximal leptin promoter and decreased association of a transcriptional factor Sp1 with this DNA region.

The role of microRNAs in cancer: diagnostic and prognostic biomarkers and targets of therapies.

INTRODUCTION: miRNAs are noncoding RNAs that target specific mRNA with subsequent regulation of particular genes, implicated in various biological processes. In cancer, miRNAs could show a different expression from normal tissues. miRNAs have a role as oncogenes when they target tumor suppressor genes and similarly they are tumor suppressors when they target oncogenes. AREAS COVERED: In this review, areas covered include the role of miRNAs in cancer diagnosis, prognosis and research for achievement of therapeutic strategies implicating miRNAs in oncology. As biogenesis of miRNAs is fundamental to understand their usefulness, this has also been discussed. Both miRNA expression profiles in cancer tissues and miRNA levels in peripheral blood were studied for improvement in the management of cancer patients. EXPERT OPINION: miRNAs have the potential for better understanding of tumor biology, but could also provide clinical advancement in management and therapy of various malignancies. The possibility of miRNA detection in peripheral blood would allow an eager expansion of their application in various clinical settings for cancer. The applicability of miRNA expression profiles still needs to be defined.

Analysis of molecular mechanisms and anti-tumoural effects of zoledronic acid in breast cancer cells.

Zoledronic acid (ZOL) is the most potent nitrogen-containing bisphosphonate (N-BPs) that strongly binds to bone mineral and acts as a powerful inhibitor of bone resorption, already clinically available for the treatment of patients with osteolytic metastases. Recent data also suggest that ZOL, used in breast cancer, may provide more than just supportive care modifying the course of the disease, though the possible molecular mechanism of action is still unclear.As breast cancer is one of the primary tumours with high propensity to metastasize to the bone, we investigated, for the first time, differential gene expression profile on Michigan Cancer Foundation-7 (MCF-7) breast cancer cells treated with low doses of ZOL (10 µM). Microarrays analysis was used to identify, describe and summarize evidence regarding the molecular basis of actions of ZOL and of their possible direct anti-tumour effects. We validated gene expression results of specific transcripts involved in major cellular process by Real Time and Western Blot analysis and we observed inhibition of proliferation and migration through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and Matrigel assay. We then focused on changes in the cytoskeletal components as fibronectin 1 (FN1), actin, and anti angiogenic compounds as transforming growth factor-ß1 (TGF-ß1) and thrombospondin 1 (THBS1). The up-regulation of these products may have an important role in inhibiting proliferation, invasion and angiogenesis mediated by ZOL.

miR-20b modulates VEGF expression by targeting HIF-1 alpha and STAT3 in MCF-7 breast cancer cells.

MicroRNAs (miRNAs) are small non-coding RNAs that regulate the expression of different genes, including genes involved in cancer progression. A functional link between hypoxia, a key feature of the tumor microenvironment, and miRNA expression has been documented. We investigated whether and how miR-20b can regulate the expression of vascular endothelial growth factor (VEGF) in MCF-7 breast cancer cells under normoxic and hypoxia-mimicking conditions (CoCl(2) exposure). Using immunoblotting, ELISA, and quantitative real-time PCR, we demonstrated that miR-20b decreased VEGF protein levels at 4 and 24 h following CoCl(2) treatment, and VEGF mRNA at 4 h of treatment. In addition, miR-20b reduced VEGF protein expression in untreated cells. Next, we investigated the molecular mechanism by which pre-miR-20b can affect VEGF transcription, focusing on hypoxia inducible factor 1 (HIF-1) and signal transducer and activator of transcription 3 (STAT3), transcriptional inducers of VEGF and putative targets of miR-20b. Downregulation of VEGF mRNA by miR-20b under a 4 h of CoCl(2) treatment was associated with reduced levels of nuclear HIF-1 alpha subunit and STAT3. Chromatin immunoprecipitation (ChIP) assays revealed that HIF-1 alpha, but not STAT3, was recruited to the VEGF promoter following the 4 h of CoCl(2) treatment. This effect was inhibited by transfection of cells with pre-miR-20b. In addition, using siRNA knockdown, we demonstrated that the presence of STAT3 is necessary for CoCl(2)-mediated HIF-1 alpha nuclear accumulation and recruitment on VEGF promoter. In summary, this report demonstrates, for the first time, that the VEGF expression in breast cancer cells is mediated by HIF-1 and STAT3 in a miR-20b-dependent manner.