MRP4 over-expression has a role on both reducing nitric oxide-dependent antiplatelet effect and enhancing ADP induced platelet activation.

The impact of inhibition of multidrug resistance protein 4 (MRP4) on nitric oxide (NO) resistance and on ADP-induced platelet aggregation is unknown. The aim of this investigation was to verify whether platelet NO resistance correlates with MRP4 expression and evaluate whether this can be reduced by in vitro MRP4 inhibition mediated by cilostazol. Moreover, we assessed if inhibition of MRP4-mediated transport reduces ADP-induced platelet reactivity.

Aspirin-Dependent Effects on Purinergic P2Y1 Receptor Expression.

Chronic treatment with aspirin in healthy volunteers (HVs) is associated with recovery of adenosine diphosphate (ADP)-induced platelet activation. The purinergic P2Y receptor exerts its effects via a G-protein, which is the same biochemical pathway activated by thromboxane-A2 receptor. We hypothesized that recovery of ADP-induced platelet activation could be attributed to increased P2Y expression induced by chronic aspirin exposure.

MiR-21 role in aspirin-dependent PPARα and multidrug resistance protein 4 upregulation.

Background: A mechanism involved in high on-aspirin treatment residual platelet reactivity is platelet multidrug resistance protein 4 (MRP4) overexpression. Aspirin enhances platelet MRP4 expression with a PPARα-dependent mechanism and reduces miR-21 expression that, in turn, downregulates PPARα expression.

Objective: The aim of our study was to verify the relationship between miR-21 and MRP4-PPARα levels induced by aspirin treatment.

Platelet miRNA-26b down-regulates multidrug resistance protein 4 in patients on chronic aspirin treatment.

Background: Multidrug resistance protein-4 (MRP4) is an ATP binding cassette membrane transporter, actively involved in the efflux of important pharmacological and physiological molecules. Recently, its over-expression has been associated with reduced aspirin (ASA) efficacy after by-pass surgery. MicroRNAs (miRNAs) are small molecules of non-coding RNA involved in the regulation of many physiological and pathophysiological pathways, are abundant in platelets, and can be modulated by several drugs.

Impact of Multidrug Resistance Protein-4 Inhibitors on Modulating Platelet Function and High on-Aspirin Treatment Platelet Reactivity.

Platelet multidrug resistance protein 4 (MRP4) plays a modulating role on platelet activation. Platelet function and thrombus formation are impaired in MRP4 knockout mice models, and, among aspirin-treated patients, high on-aspirin residual platelet reactivity (HARPR) positively correlates with MRP4 levels. To better understand the effects of MRP4 on platelet function, the aim of this investigation was to assess the impact of cilostazol-induced inhibition of MRP4-mediated transport and assess aspirin-induced antiplatelet effects and rates of HARPR in human subjects.

From Human Megakaryocytes to Platelets: Effects of Aspirin on High-Mobility Group Box 1/Receptor for Advanced Glycation End Products Axis.

Platelets (PLTs) are the major source of high-mobility group box 1 (HMGB1), a protein that is involved in sterile inflammation of blood vessels and thrombosis. Megakaryocytes (MKs) synthesize HMGB1 and transfer both protein and mRNA into PLTs and PLT-derived microvesicles (MV). Free HMGB1 found in supernatants of differentiated MKs and in a megakaryoblastic cell line (DAMI cells).

Enhanced platelet MRP4 expression and correlation with platelet function in patients under chronic aspirin treatment.

Platelet multidrug resistance protein4 (MRP4)-overexpression has a role in reducing aspirin action. Aspirin in vivo treatment enhances platelet MRP4 expression and MRP4 mediated transport inhibition reduces platelet function and delays thrombus formation. The aim of our work was to verify whether MRP4 expression is enhanced in platelets obtained from patients under chronic aspirin treatment and whether it correlates with residual platelet reactivity.

Action of HMGB1 on miR-221/222 cluster in neuroblastoma cell lines.

microRNA (miR/miRNA) are small non-coding RNAs that control gene expression at the post-transcriptional level by targeting mRNAs. Aberrant expression of miRNAs is often observed in different types of cancer. Specific miRNAs function as tumor suppressors or oncogenes and interfere with various aspects of carcinogenesis, including differentiation, proliferation and invasion.

Impact of chronic exposure to bevacizumab on EpCAM-based detection of circulating tumor cells.

Background: Circulating tumor cells (CTCs) are often undetected through the immunomagnetic epithelial cell adhesion molecule (EpCAM)-based CellSearch(®) System in breast and colorectal cancer (CRC) patients treated with bevacizumab (BEV), where low CTC numbers have been reported even in patients with evidence of progression of disease. To date, the reasons for this discrepancy have not been clarified. This study was carried out to investigate the molecular and phenotypic changes in CRC cells after chronic exposure to BEV in vitro.

Multidrug Resistance Protein-4 Influences Aspirin Toxicity in Human Cell Line.

Overexpression of efflux transporters, in human cells, is a mechanism of resistance to drug and also to chemotherapy. We found that multidrug resistance protein-4 (MRP4) overexpression has a role in reducing aspirin action in patients after bypass surgery and, very recently, we found that aspirin enhances platelet MRP4 levels through peroxisome proliferator activated receptor-α (PPARα). In the present paper, we verified whether exposure of human embryonic kidney-293 cells (Hek-293) to aspirin modifies MRP4 gene expression and its correlation with drug elimination and cell toxicity.

Nonsteroidal anti-inflammatory drugs in-vitro and in-vivo treatment and Multidrug Resistance Protein 4 expression in human platelets.

Platelet Multidrug Resistance Protein 4 (MRP4)-overexpression has a role in reducing aspirin action in patients after by-pass surgery. Aspirin induces platelet MRP4 over-expression, through megakaryocytes genomic modulation. Aim of our work was to verify whether other non-steroidal antiinflammatory drugs (NSAIDs) enhance platelet MRP4 expression and evaluate platelet function in patients who overexpressed MRP4.

Arachidonic acid-stimulated platelet tests: Identification of patients less sensitive to aspirin treatment.

Serum thromboxane-B2 (TxB2), together with arachidonic acid (AA)-induced platelet aggregation, are, at the moment, the most used tests to identify patients displaying high on-aspirin treatment platelet reactivity (HAPR). Both tests are specific for aspirin action on cyclooxygenase-1. While the correlation between serum TxB2 assay and clinical outcome is established, data are conflicting with regard to aspirin treatment and a possible association with AA-stimulated platelet markers and clinical outcome.

Aspirin influences megakaryocytic gene expression leading to up-regulation of multidrug resistance protein-4 in human platelets.

Aim: The aim of the study was to investigate whether human megakaryocytic cells have an adaptive response to aspirin treatment, leading to an enhancement of multidrug resistance protein-4 (MRP4) expression in circulating platelets responsible for a reduced aspirin action. We recently found that platelet MRP4 overexpression has a role in reducing aspirin action in patients after by-pass surgery. Aspirin enhances MRP4-mRNA levels in rat liver and drug administration transcriptionally regulates MRP4 gene expression through peroxisome proliferator-activated receptor-α (PPARα).

A functional interaction between TRPC/NCKX induced by DAG plays a role in determining calcium influx independently from PKC activation.

Ca(2+)influx might occur through K(+)-dependent Na(+)/Ca(2+) exchanger operating in reverse mode (rNCKX). In a cellular model different from platelets, an interaction between canonical transient receptor potential cation (TRPC) channels and NCX has been found. The aim of this study was to verify whether the TRPC/NCKX interaction operates in human platelets.

The HMGA1 protoncogene frequently deregulated in cancer is a transcriptional target of E2F1.

Reactivation of the HMGA1 protoncogene is very frequent in human cancer, but still very little is known on the molecular mechanisms leading to this event. Prompted by the finding of putative E2F binding sites in the human HMGA1 promoter and by the frequent deregulation of the RB/E2F1 pathway in human carcinogenesis, we investigated whether E2F1 might contribute to the regulation of HMGA1 gene expression. Here we report that E2F1 induces HMGA1 by interacting with a 193 bp region of the HMGA1 promoter containing an E2F binding site surrounded by three putative Sp1 binding sites.

MYCN sensitizes human neuroblastoma to apoptosis by HIPK2 activation through a DNA damage response.

MYCN amplification occurs in approximately 20% of human neuroblastomas and is associated with early tumor progression and poor outcome, despite intensive multimodal treatment. However, MYCN overexpression also sensitizes neuroblastoma cells to apoptosis. Thus, uncovering the molecular mechanisms linking MYCN to apoptosis might contribute to designing more efficient therapies for MYCN-amplified tumors.

MiR-128 up-regulation inhibits Reelin and DCX expression and reduces neuroblastoma cell motility and invasiveness.

MicroRNAs are a class of sophisticated regulators of gene expression, acting as post-transcriptional inhibitors that recognize their target mRNAs through base pairing with short regions along the 3'UTRs. Several microRNAs are tissue specific, suggesting a specialized role in tissue differentiation or maintenance, and quite a few are critically involved in tumorigenesis. We studied miR-128, a brain-enriched microRNA, in retinoic acid-differentiated neuroblastoma cells, and we found that this microRNA is up-regulated in treated cells, where it down-modulates the expression of two proteins involved in the migratory potential of neural cells: Reelin and DCX.

Human papilloma virus-dependent HMGA1 expression is a relevant step in cervical carcinogenesis.

HMGA1 is a member of a small family of architectural transcription factors involved in the coordinate assembly of multiprotein complexes referred to as enhanceosomes. In addition to their role in cell proliferation, differentiation, and development, high-mobility group proteins of the A type (HMGA) family members behave as transforming protoncogenes either in vitro or in animal models. Recent reports indicated that HMGA1 might counteract p53 pathway and provided an interesting hint on the mechanisms determining HMGA's transforming potential.

Molecular mechanism of HMGA1 deregulation in human neuroblastoma.

Very soon after their original identification in HeLa cells in 1983, HMGA proteins appeared as interesting cancer-related molecules. Indeed, they were immediately noted as a sub-class of High Mobility Group proteins induced in fibroblast or epithelial cells transformed with sarcoma viruses. After more than 20 years, the association between HMGA protein expressions and cellular transformation has been largely confirmed and HMGA are among the most widely expressed cancer-associated proteins.

Identification of a novel maturation mechanism and restricted substrate specificity for the SspB cysteine protease of Staphylococcus aureus.

The SspB cysteine protease of Staphylococcus aureus is expressed in an operon, flanked by the sspA serine protease, and sspC, encoding a 12.9-kDa protein of unknown function. SspB was expressed as a 40-kDa prepropeptide pSspB, which did not undergo autocatalytic maturation.