Recent studies have reported the emerging role of microRNAs (miRNAs) in human cancers. We systematically characterized miRNA expression and editing in the human brain, which displays the highest number of A-to-I RNA editing sites among human tissues, and in de novo glioblastoma brain cancer. We identified 299 miRNAs altered in their expression and 24 miRNAs differently edited in human brain compared to glioblastoma tissues. We focused on the editing site within the miR-589–3p seed. MiR-589–3p is a unique miRNA almost fully edited (∼100%) in normal brain and with a consistent editing decrease in glioblastoma. The edited version of miR-589–3p inhibits glioblastoma cell proliferation, migration and invasion, while the unedited version boosts cell proliferation and motility/invasion, thus being a potential cancer-promoting factor. We demonstrated that the editing of this miRNA is mediated by ADAR2, and retargets miR-589–3p from the tumor-suppressor PCDH9 to ADAM12, which codes for the metalloproteinase 12 promoting glioblastoma invasion. Overall, our study dissects the role of a unique brain-specific editing site within miR-589–3p, with important anticancer features, and highlights the importance of RNA editing as an essential player not only for diversifying the genomic message but also for correcting not-tolerable/critical genomic coding sites.

Purpose: The Epstein–Barr virus (EBV) is present in the malignant Hodgkin/Reed–Sternberg (HRS) cells of 20% to 40% cases of Hodgkin lymphoma (HL) in Western countries. We were interested in the detection and quantification of cell-free plasma EBV-DNA as an indicator of biological and clinical characteristics in EBV-associated HL. Experimental Design: EBV was detected in peripheral blood compartments (whole blood, plasma, and mononuclear cells) at diagnosis by real-time PCR for the EBNA (EB nuclear antigen) region (n = 93) and in HRS cells by in situ hybridization for EBV-encoded small RNAs (EBER; n = 63). These data were correlated to histological and clinical characteristics, EBV serology, circulating cell-free DNA, and interleukin (IL)-6 levels. Results: Detection of EBV-DNA in plasma had a high specificity (90%), but a relatively low sensitivity (65%) to predict for EBV association. The viral load was higher in patients with advanced stage disease, older age in the presence of B-symptoms, and international prognostic score more than 2. The presence of EBV in HRS cells and higher plasma EBV-DNA copy numbers correlated to an increased frequency of tumor-infiltrating CD68+ macrophages in lymph node biopsies. Plasma EBV-DNA load correlated to circulating cell-free DNA and IL-6 levels, and inversely correlated to lymphocyte counts and EBNA1 antibody titers. Conclusion: Although the presence of EBV-DNA in peripheral blood cannot be regarded as a surrogate marker for EBER, the plasma EBV-DNA load at HL diagnosis is an indicator of disease activity and biological characteristics associated with negative prognosis. Moreover, the inverse correlation to EBNA1 antibody titers and lymphocyte counts may indicate a reduction in immunosurveillance, favoring the expansion of EBV-HRS cells in HL. Clin Cancer Res; 17(9); 2885–92. ©2011 AACR.

BACKGROUND: Inhibitors of DNA binding/differentiation (Id1 to Id4) are a family of helix‐loop‐helix transcription factors, which are highly expressed during embryogenesis and at lower levels in mature tissues. Id4 plays an important role in neuronal stem cell differentiation, and its deregulation has been implicated in glial neoplasia.METHODS: The methylation status of Id4 was analyzed by methylation‐specific polymerase chain reaction (PCR) in 62 glioblastoma (GBM) cases and in 20 normal brain tissues. Methylation status of Id4 was confirmed by sequencing after subcloning and messenger RNA (mRNA) and protein expression. We also evaluated the mRNA expression of MGP (matrix GLA protein), TGF‐β1 (transforming growth factor beta 1), and VEGF (vascular endothelial growth factor) by real‐time PCR analysis. Clinical and histological assessment of tumor angiogenesis was performed by evaluating the relative enhancing tumor ratio on magnetic resonance imaging and microvessel density on von Willebrand factor–stained sections, respectively.RESULTS: The promoter of Id4 was methylated in 23 of 62 (37%) GBMs. In methylated GBMs, Id4 mRNA was significantly reduced, compared with unmethylated GBMs (P = .0002). A significant reduction of protein expression was detected in all hypermethylated cases. GBMs with methylated Id4 showed a significant reduction of MGP, TGF‐β1, and VEGF mRNA expression and had significantly lower relative enhancing tumor ratio (P = .0108) and microvessel density (P = .0241) values with respect to unmethylated GBMs. Finally, Id4 methylation was significantly associated with a favorable clinical outcome (P = .0006).CONCLUSIONS: These data suggest that methylation of Id4 may be involved in the pathogenesis of GBM and in the resistance of this neoplasm to conventional treatment throughout MGP‐mediated neoangiogenesis. Cancer 2013. © 2012 American Cancer Society

Type 5 phosphodiesterase regulates glioblastoma multiforme aggressiveness and clinical outcome Type 5 phosphodiesterase regulates glioblastoma multiforme aggressiveness and clinical outcome

Glioblastoma (GBM) is the most aggressive, infiltrative, and lethal brain tumor in humans. Despite the extensive advancement in the knowledge about tumor progression and treatment over the last few years, the prognosis of GBM is still very poor due to the difficulty of targeting drugs or anticancer molecules to GBM cells. The major challenge in improving GBM treatment implicates the development of a targeted drug delivery system, capable of crossing the blood–brain barrier (BBB) and specifically targeting GBM cells. Aptamers possess many characteristics that make them ideal novel therapeutic agents for the treatment of GBM. They are short single-stranded nucleic acids (RNA or ssDNA) able to bind to a molecular target with high affinity and specificity. Several GBM-targeting aptamers have been developed for imaging, tumor cell isolation from biopsies, and drug/anticancer molecule delivery to the tumor cells. Due to their properties (low immunogenicity, long stability, and toxicity), a large number of aptamers have been selected against GBM biomarkers and tested in GBM cell lines, while only a few of them have also been tested in in vivo models of GBM. Herein, we specifically focus on aptamers tested in GBM in vivo models that can be considered as new diagnostic and/or therapeutic tools for GBM patients’ treatment.

Both fibroblast growth factor 9 (Fgf9) and Kit Ligand (Kl) signal through tyrosine kinase receptors, yet they exert opposite effects on meiotic differentiation in postnatal spermatogonia, Fgf9 acting as a meiosis-inhibiting substance and Kl acting as a promoter of the differentiation process. To understand the molecular mechanisms that might underlie this difference, we tried to dissect the intracellular signaling elicited by these two growth factors. We found that both Fgf9 and Kl stimulate Erk1/2 activation in Kit+ (differentiating) spermatogonia, even though with different time courses, whereas Kl, but not Fgf9, elicits activation of the Pi3k-Akt pathway. Sustained Erk1/2 activity promoted by Fgf9 is required for induction of the autocrine Cripto-Nodal-Smad2/3 signaling loop in these cells. Nodal signaling, in turn, is essential to mediate Fgf9 suppression of the meiotic program, including inhibition of Stra8 and Scp3 expression and induction of the meiotic gatekeeper Nanos2. On the contrary, sustained activation of the Pi3k-Akt pathway is required for the induction of Stra8 expression elicited by Kl and retinoic acid. Moreover, we found that Kl treatment impairs Nodal mRNA expression and Fgf9-mediated Nanos2 induction, reinforcing the antagonistic effect of these two growth factors on the meiotic fate of male germ cells.