Danilo Fiore

Impact of a High Loading Dose of Atorvastatin on Contrast-Induced Acute Kidney Injury

Background— The role of statins in the prevention of contrast-induced acute kidney injury (CIAKI) is controversial. Methods and Results— First, we investigated the in vivo effects of atorvastatin on CIAKI. Patients with chronic kidney disease enrolled in the Novel Approaches for Preventing or Limiting Events (NAPLES) II trial were randomly assigned to (1) the atorvastatin group (80 mg within 24 hours before contrast media [CM] exposure; n=202) or (2) the control group (n=208). All patients received a high dose of N-acetylcysteine and sodium bicarbonate solution. Second, we investigated the in vitro effects of atorvastatin pretreatment on CM-mediated modifications of intracellular pathways leading to apoptosis or survival in renal tubular cells. CIAKI (ie, an increase >10% of serum cystatin C concentration within 24 hours after CM exposure) occurred in 9 of 202 patients in the atorvastatin group (4.5%) and in 37 of 208 patients in the control group (17.8%) (P=0.005; odds ratio=0.22; 95% confidence interval, 0.07–0.69). CIAKI rate was lower in the atorvastatin group in both diabetics and nondiabetics and in patients with moderate chronic kidney disease (estimated glomerular filtration rate, 31–60 mL/min per 1.73 m2). In the in vitro model, pretreatment with atorvastatin (1) prevented CM-induced renal cell apoptosis by reducing stress kinases activation and (2) restored the survival signals (mediated by Akt and ERK pathways). Conclusions— A single high loading dose of atorvastatin administered within 24 hours before CM exposure is effective in reducing the rate of CIAKI. This beneficial effect is observed only in patients at low to medium risk.

Effect of miR-21 and miR-30b/c on TRAIL-induced apoptosis in glioma cells

Glioblastoma is the most frequent brain tumor in adults and is the most lethal form of human cancer. Despite the improvements in treatments, survival of patients remains poor. To define novel pathways that regulate susceptibility to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) in glioma, we have performed genome-wide expression profiling of microRNAs (miRs). We show that in TRAIL-resistant glioma cells, levels of different miRs are increased, and in particular, miR-30b/c and -21. We demonstrate that these miRs impair TRAIL-dependent apoptosis by inhibiting the expression of key functional proteins. T98G-sensitive cells treated with miR-21 or -30b/c become resistant to TRAIL. Furthermore, we demonstrate that miR-30b/c and miR-21 target respectively the 3′ untranslated region of caspase-3 and TAp63 mRNAs, and that those proteins mediate some of the effects of miR-30 and -21 on TRAIL resistance, even in human glioblastoma primary cells and in lung cancer cells. In conclusion, we show that high expression levels of miR-21 and -30b/c are needed to maintain the TRAIL-resistant phenotype, thus making these miRs as promising therapeutic targets for TRAIL resistance in glioma.

In vivo and in vitro assessment of pathways involved in contrast media-induced renal cells apoptosis

Contrast-induced nephropathy accounts for >10% of all causes of hospital-acquired renal failure, causes a prolonged in-hospital stay and represents a powerful predictor of poor early and late outcome. Mechanisms of contrast-induced nephropathy are not completely understood. In vitro data suggests that contrast media (CM) induces a direct toxic effect on renal tubular cells through the activation of the intrinsic apoptotic pathway. It is unclear whether this effect has a role in the clinical setting. In this work, we evaluated the effects of CM both in vivo and in vitro. By analyzing urine samples obtained from patients who experienced contrast-induced acute kidney injury (CI-AKI), we verified, by western blot and immunohistochemistry, that CM induces tubular renal cells apoptosis. Furthermore, in cultured cells, CM caused a dose–response increase in reactive oxygen species (ROS) production, which triggered Jun N-terminal kinases (JNK1/2) and p38 stress kinases marked activation and thus apoptosis. Inhibition of JNK1/2 and p38 by different approaches (i.e. pharmacological antagonists and transfection of kinase-death mutants of the upstream p38 and JNK kinases) prevented CM-induced apoptosis. Interestingly, N-acetylcysteine inhibited ROS production, and thus stress kinases and apoptosis activation. Therefore, we conclude that CM-induced tubular renal cells apoptosis represents a key mechanism of CI-AKI.

MiR-221/222 target the DNA methyltransferase MGMT in glioma cells.

Glioblastoma multiforme (GBM) is one of the most deadly types of cancer. To date, the best clinical approach for treatment is based on administration of temozolomide (TMZ) in combination with radiotherapy. Much evidence suggests that the intracellular level of the alkylating enzyme O6-methylguanine–DNA methyltransferase (MGMT) impacts response to TMZ in GBM patients. MGMT expression is regulated by the methylation of its promoter. However, evidence indicates that this is not the only regulatory mechanism present. Here, we describe a hitherto unknown microRNA-mediated mechanism of MGMT expression regulation. We show that miR-221 and miR-222 are upregulated in GMB patients and that these paralogues target MGMT mRNA, inducing greater TMZ-mediated cell death. However, miR-221/miR-222 also increase DNA damage and, thus, chromosomal rearrangements. Indeed, miR-221 overexpression in glioma cells led to an increase in markers of DNA damage, an effect rescued by re-expression of MGMT. Thus, chronic miR-221/222-mediated MGMT downregulation may render cells unable to repair genetic damage. This, associated also to miR-221/222 oncogenic potential, may poor GBM prognosis.

Cancer-associated fibroblasts release exosomal microRNAs that dictate an aggressive phenotype in breast cancer.

Cancer-associated fibroblasts (CAFs) are the major components of the tumor microenvironment. They may drive tumor progression, although the mechanisms involved are still poorly understood. Exosomes have emerged as important mediators of intercellular communication in cancer. They mediate horizontal transfer of microRNAs (miRs), mRNAs and proteins, thus affecting breast cancer progression. Differential expression profile analysis identified three miRs (miRs -21, -378e, and -143) increased in exosomes from CAFs as compared from normal fibroblasts. Immunofluorescence indicated that exosomes may be transferred from CAFs to breast cancer cells, releasing their cargo miRs. Breast cancer cells (BT549, MDA-MB-231, and T47D lines) exposed to CAF exosomes or transfected with those miRs exhibited a significant increased capacity to form mammospheres, increased stem cell and epithelial-mesenchymal transition (EMT) markers, and anchorage-independent cell growth. These effects were reverted by transfection with anti-miRs. Similarly to CAF exosomes, normal fibroblast exosomes transfected with miRs -21, -378e, and -143 promoted the stemness and EMT phenotype of breast cancer cells. Thus, we provided evidence for the first time of the role of CAF exosomes and their miRs in the induction of the stemness and EMT phenotype in different breast cancer cell lines. Indeed, CAFs strongly promote the development of an aggressive breast cancer cell phenotype.

Aptamer-miRNA-212 Conjugate Sensitizes NSCLC Cells to TRAIL.

TNF-related apoptosis-inducing ligand (TRAIL) is a promising antitumor agent for its remarkable ability to selectively induce apoptosis in cancer cells, without affecting the viability of healthy bystander cells. The TRAIL tumor suppressor pathway is deregulated in many human malignancies including lung cancer. In human non-small cell lung cancer (NSCLC) cells, sensitization to TRAIL therapy can be restored by increasing the expression levels of the tumor suppressor microRNA-212 (miR-212) leading to inhibition of the anti-apoptotic protein PED/PEA-15 implicated in treatment resistance. In this study, we exploited a previously described RNA aptamer inhibitor of the tyrosine kinase receptor Axl (GL21.T) expressed on lung cancer cells, as a means to deliver miR-212 into human NSCLC cells expressing Axl. We demonstrate efficient delivery of miR-212 following conjugation of the miR to GL21.T (GL21.T-miR212 chimera). We show that the chimera downregulates PED and restores TRAIL-mediate cytotoxicity in cancer cells. Importantly, treatment of Axl+ lung cancer cells with the chimera resulted in (i) an increase in caspase activation and (ii) a reduction of cell viability in combination with TRAIL therapy. In conclusion, we demonstrate that the GL21.T-miR212 chimera can be employed as an adjuvant to TRAIL therapy for the treatment of lung cancer.

MiR-221 promotes stemness of breast cancer cells by targeting DNMT3b

Cancer stem cells (CSCs) are a small part of the heterogeneous tumor cell population possessing self-renewal and multilineage differentiation potential as well as a great ability to sustain tumorigenesis. The molecular pathways underlying CSC phenotype are not yet well characterized. MicroRNAs (miRs) are small noncoding RNAs that play a powerful role in biological processes. Early studies have linked miRs to the control of self-renewal and differentiation in normal and cancer stem cells. We aimed to study the functional role of miRs in human breast cancer stem cells (BCSCs), also named mammospheres. We found that miR-221 was upregulated in BCSCs compared to their differentiated counterpart. Similarly, mammospheres from T47D cells had an increased level of miR-221 compared to differentiated cells. Transfection of miR-221 in T47D cells increased the number of mammospheres and the expression of stem cell markers. Among miR-221s targets, we identified DNMT3b. Furthermore, in BCSCs we found that DNMT3b repressed the expression of various stemness genes, such as Nanog and Oct 3/4, acting on the methylation of their promoters, partially reverting the effect of miR-221 on stemness. We hypothesize that miR-221 contributes to breast cancer tumorigenicity by regulating stemness, at least in part through the control of DNMT3b expression.

Contrast-induced acute kidney injury: potential new strategies.

Purpose of reviewContrast-induced acute kidney injury (CI-AKI) is an impairment of renal function following contrast media administration in the absence of an alternative cause. It represents a powerful predictor of poor early and late outcomes. Here, we review the major strategies to prevent CI-AKI. Recent findingsHydration represents the gold standard as a prophylactic measure to prevent CI-AKI, acting by increasing urine flow rate and, thereby, by limiting the time of contact between the contrast media and the tubular epithelial cells. An optimal hydration regimen should be defined according to predefined clinical markers, such as urine flow rate, or left ventricular end-diastolic pressure. Recently, high-dose statins pretreatment has been included in the guidelines of CI-AKI prevention. However, uncertainty still exists on the efficacy of several compounds tested in both observational trials and randomized studies to prevent CI-AKI. Compounds evaluated include diuretics (furosemide), antioxidants (i.e. N-acetylcysteine and statins) and vasodilators (i.e. calcium antagonists, dopamine and fenoldopam). SummaryHydration still represents the most reliable strategy to prevent CI-AKI. New prophylactic strategies for acute kidney injury are still under investigation.

Therapeutic strategies to prevent contrast-induced acute kidney injury.

Purpose of review Contrast-induced acute kidney injury (CI-AKI) accounts for approximately 10% of all causes of hospital-acquired renal failure, causes a prolonged in-hospital stay, and represents a powerful predictor of poor early and late outcome. Here, we highlight endpoints used to assess major strategies to prevent CI-AKI. Recent findings A general consensus exists on the beneficial prophylactic effect of hydration. This seems to act by increasing urine flow rate and, thereby, by limiting the time of contact between the contrast media and the epithelial tubular cells. On the contrary, both observational trials and randomized studies are often controversial in their conclusions on the efficacy of several drugs tested to prevent CI-AKI. Compounds evaluated include diuretics (furosemide), antioxidants (i.e., N-acetylcysteine and statins), and vasodilators (i.e., calcium antagonists, dopamine, and fenoldopam). Due to the negative and/or controversial clinical results, none of these drugs has been currently recommended to prevent CI-AKI. Conclusion More reliable markers of acute kidney injury and new prophylactic strategies are warranted to prevent the incidence of CI-AKI.

RYK promotes the stemness of glioblastoma cells via the WNT/ β-catenin pathway

Glioblastoma multiforme (GBM) is characterized by a strong self-renewal potential and a poor differentiation state. Since receptor-like tyrosine kinase (RYK) activates the WNT/β-catenin pathway essential for cancer stem cell maintenance, we evaluated its contribution in conferring stemness to GBM cells. Here, we report that Ryk (related-to-receptor tyrosine kinase), an atypical tyrosine kinase receptor, is upregulated in samples from GBM patients as well as in GSCs. Ryk overexpression confers stemness properties to GBM cells through the modulation of the canonical Wnt signaling and by promoting the activation of pluripotency-related transcription factor circuitry and neurosphere formation ability. In contrast, siRNA-mediated knockdown of Ryk expression suppresses this stem-like phenotype. Rescue experiments reveal that stemness-promoting activity of Ryk is attributable, at least in part, to β-catenin stabilization. Furthermore, Ryk overexpression improves cell motility and anchorage independent cell growth. Taken together, our findings demonstrate that Ryk promotes stem cell-like and tumorigenic features to glioma cells its essential for the maintenance of GSCs and could be a target of novel therapies.