Transcriptional activation of the miR-17-92 cluster is involved in the growth-promoting effects of MYB in human Ph-positive leukemia cells.

MicroRNAs, non-coding regulators of gene expression, are likely to function as important downstream effectors of many transcription factors including MYB. Optimal levels of MYB are required for transformation/maintenance of BCR-ABL-expressing cells. We investigated whether MYB silencing modulates microRNA expression in Philadelphia-positive (Ph+) leukemia cells and if MYB-regulated microRNAs are important for the MYB addiction of these cells. Thirty-five microRNAs were modulated by MYB silencing in lymphoid and erythromyeloid chronic myeloid leukemia-blast crisis BV173 and K562 cells; 15 of these were concordantly modulated in both lines. We focused on the miR-17-92 cluster because of its oncogenic role in tumors and found that: i) it is a direct MYB target; ii) it partially rescued the impaired proliferation and enhanced apoptosis of MYB-silenced BV173 cells. Moreover, we identified FRZB, a Wnt/β-catenin pathway inhibitor, as a novel target of the miR-17-92 cluster. High expression of MYB in blast cells from 2 Ph+leukemia patients correlated positively with the miR-17-92 cluster and inversely with FRZB. This expression pattern was also observed in a microarray dataset of 122 Ph+acute lymphoblastic leukemias. In vivo experiments in NOD scid gamma mice injected with BV173 cells confirmed that FRZB functions as a Wnt/β-catenin inhibitor even as they failed to demonstrate that this pathway is important for BV173-dependent leukemogenesis. These studies illustrate the global effects of MYB expression on the microRNAs profile of Ph+cells and supports the concept that the MYB addiction of these cells is, in part, caused by modulation of microRNA-regulated pathways affecting cell proliferation and survival. Copyright© 2019 Ferrata Storti Foundation

The Neuroprotective Effects of 17β-Estradiol Pretreatment in a Model of Neonatal Hippocampal Injury Induced by Trimethyltin

Hippocampal dysfunction plays a central role in neurodevelopmental disorders, resulting in severe impairment of cognitive abilities, including memory and learning. On this basis, developmental studies represent an important tool both to understanding the cellular and molecular phenomena underlying early hippocampal damage and to study possible therapeutic interventions, that may modify the progression of neuronal death. Given the modulatory role played by 17β-estradiol (E2) on hippocampal functions and its neuroprotective properties, the present study investigates the effects of pretreatment with E2 in a model of neonatal hippocampal injury obtained by trimethyltin (TMT) administration, characterized by neuronal loss in CA1 and CA3 subfields and astroglial and microglial activation. At post-natal days (P)5 and P6 animals received E2 administration (0.2 mg/kg/die i.p.) or vehicle. At P7 they received a single dose of TMT (6.5 mg/kg i.p.) and were sacrificed 72 h (P10) or 7 days after TMT treatment (P14). Our findings indicate that pretreatment with E2 exerts a protective effect against hippocampal damage induced by TMT administration early in development, reducing the extent of neuronal death in the CA1 subfield, inducing the activation of genes involved in neuroprotection, lowering the neuroinflammatory response and restoring neuropeptide Y- and parvalbumin- expression, which is impaired in the early phases of TMT-induced damage. Our data support the efficacy of estrogen-based neuroprotective approaches to counteract early occurring hippocampal damage in the developing hippocampus

Glioblastoma endothelium drives bevacizumab-induced infiltrative growth via modulation of PLXDC1

Bevacizumab, a VEGF-targeting monoclonal antibody, may trigger an infiltrative growth pattern in glioblastoma. We investigated this pattern using both a human specimen and rat models. In the human specimen, a substantial fraction of infiltrating tumor cells were located along perivascular spaces in close relationship with endothelial cells. Brain xenografts of U87MG cells treated with bevacizumab were smaller than controls (p = 0.0055; Student t-test), however, bands of tumor cells spread through the brain farther than controls (p < 0.001; Student t-test). Infiltrating tumor Cells exhibited tropism for vascular structures and propensity to form tubules and niches with endothelial cells. Molecularly, bevacizumab triggered an epithelial to mesenchymal transition with over-expression of the receptor Plexin Domain Containing 1 (PLXDC1). These results were validated using brain xenografts of patient-derived glioma stem-like cells. Enforced expression of PLXDC1 in U87MG cells promoted brain infiltration along perivascular spaces. Importantly, PLXDC1 inhibition prevented perivascular infiltration and significantly increased the survival of bevacizumab-treated rats. Our study indicates that bevacizumab-induced brain infiltration is driven by vascular endothelium and depends on PLXDC1 activation of tumor cells

Deregulated expression of the imprinted DLK1-DIO3 region in Glioblastoma Stem-like Cells: tumor suppressor role of lncRNA MEG3

Background: Glioblastoma (GBM) stem-like cells (GSCs) are thought to be responsible for the maintenance and aggressiveness of GBM, the most common primary brain tumor in adults. This study aims at elucidating the involvement of deregulations within the imprinted DLK-DIO3 region on chromosome 14q32 in GBM pathogenesis. Methods: RT-PCR analyses were performed on GSCs and GBM tissues. Methylation analyses, gene expression and Reverse-Phase protein Array profiles were used to investigate the tumor suppressor function of MEG3. Results: Loss of expression of genes and non-coding RNAs within the DLK1-DIO3 region was observed in GSCs and GBM tissues compared to normal brain. This down-regulation is mainly mediated by epigenetic silencing. Kaplan-Meier analysis indicated that low expression of MEG3 and MEG8 lncRNAs significantly correlated with short survival in GBM patients. MEG3 restoration impairs tumorigenic abilities of GSCs in vitro by inhibiting cell growth, migration and colony formation and decreases in vivo tumor growth reducing infiltrative growth. These effects were associated with modulation of genes involved in cell adhesion and Epithelial to Mesenchymal Transition (EMT). Conclusions: In GBM, MEG3 acts as a tumor-suppressor mainly regulating cell adhesion, EMT and cell proliferation, thus providing a potential candidate for novel GBM therapies

The neuroprotective effects of 17β-estradiol pretreatment in a model of neonatal hippocampal injury induced by trimethyltin

Hippocampal dysfunction plays a central role in neurodevelopmental disorders, resulting in severe impairment of cognitive abilities, including memory and learning. On this basis, developmental studies represent an important tool both to understanding the cellular and molecular phenomena underlying early hippocampal damage and to study possible therapeutic interventions, that may modify the progression of neuronal death. Given the modulatory role played by 17β-estradiol (E2) on hippocampal functions and its neuroprotective properties, the present study investigates the effects of pretreatment with E2 in a model of neonatal hippocampal injury obtained by trimethyltin (TMT) administration, characterized by neuronal loss in CA1 and CA3 subfields and astroglial and microglial activation. At post-natal days (P)5 and P6 animals received E2 administration (0.2 mg/kg/die i.p.) or vehicle. At P7 they received a single dose of TMT (6.5 mg/kg i.p.) and were sacrificed 72 h (P10) or 7 days after TMT treatment (P14). Our findings indicate that pretreatment with E2 exerts a protective effect against hippocampal damage induced by TMT administration early in development, reducing the extent of neuronal death in the CA1 subfield, inducing the activation of genes involved in neuroprotection, lowering the neuroinflammatory response and restoring neuropeptide Y- and parvalbumin- expression, which is impaired in the early phases of TMT-induced damage. Our data support the efficacy of estrogen-based neuroprotective approaches to counteract early occurring hippocampal damage in the developing hippocampus

Bone marrow‐derived mesenchymal stem cells promote invasiveness and transendothelial migration of osteosarcoma cells via a mesenchymal to amoeboid transition

There is growing evidence to suggest that bone marrow‐derived mesenchymal stem cells (BM‐MSCs) are key players in tumour stroma. Here, we investigated the cross‐talk between BM‐MSCs and osteosarcoma (OS) cells. We revealed a strong tropism of BM‐MSCs towards these tumour cells and identified monocyte chemoattractant protein (MCP)‐1, growth‐regulated oncogene (GRO)‐α and transforming growth factor (TGF)‐β1 as pivotal factors for BM‐MSC chemotaxis. Once in contact with OS cells, BM‐MSCs trans‐differentiate into cancer‐associated fibroblasts, further increasing MCP‐1, GRO‐α, interleukin (IL)‐6 and IL‐8 levels in the tumour microenvironment. These cytokines promote mesenchymal to amoeboid transition (MAT), driven by activation of the small GTPase RhoA, in OS cells, as illustrated by the in vitro assay and live imaging. The outcome is a significant increase of aggressiveness in OS cells in terms of motility, invasiveness and transendothelial migration. In keeping with their enhanced transendothelial migration abilities, OS cells stimulated by BM‐MSCs also sustain migration, invasion and formation of the in vitro capillary network of endothelial cells. Thus, BM‐MSC recruitment to the OS site and the consequent cytokine‐induced MAT are crucial events in OS malignancy

Transcriptional silencing of the ETS1 oncogene contributes to human granulocytic differentiation

Ets-1 is a widely expressed transcription factor implicated in several biological processes including hematopoiesis, where it contributes to the regulation of cellular differentiation. The functions of Ets-1 are regulated by transcription factors as well as by phosphorylation events: phosphorylation of threonine 38 activates Ets-1, whereas phosphorylation of a cluster of serines within exon VII reduces DNA binding activity. This study focuses on the role of Ets-1 during granulocytic differentiation of NB4 promyelocytic and HL60 myeloblastic leukemia cell lines induced by all-trans retinoic acid