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Simple Summary Adenosine to inosine (A-to-I) editing is a type of RNA editing where individual adenosines are enzymatically converted into inosines. A-to-I RNA editing plays an important role in cancer biology. Several studies have demonstrated that A-to-I editing of microRNAs (miRNAs) very often affect miRNA function as oncosuppressors or oncogenes, hence showing clinical relevance. Hence, A-to-I miRNA editing has been suggested as a potential diagnostic and prognostic tool in the monitoring of cancer patients. Nevertheless, the process of identifying and characterizing miRNA editing events in tumor samples still presents several challenges. In this review, we outline molecular aspects linked to miRNA A-to-I editing and retrace methods and approaches dedicated to detection of editing sites and functional characterization of edited miRNAs in cancer. Abstract Adenosine to inosine (A-to-I) editing consists of an RNA modification where single adenosines along the RNA sequence are converted into inosines. Such a biochemical transformation is catalyzed by enzymes belonging to the family of adenosine deaminases acting on RNA (ADARs) and occurs either co- or post-transcriptionally. The employment of powerful, high-throughput detection methods has recently revealed that A-to-I editing widely occurs in non-coding RNAs, including microRNAs (miRNAs). MiRNAs are a class of small regulatory non-coding RNAs (ncRNAs) acting as translation inhibitors, known to exert relevant roles in controlling cell cycle, proliferation, and cancer development. Indeed, a growing number of recent researches have evidenced the importance of miRNA editing in cancer biology by exploiting various detection and validation methods. Herein, we briefly overview early and currently available A-to-I miRNA editing detection and validation methods and discuss the significance of A-to-I miRNA editing in human cancer.

Protein tyrosine phosphatase receptor type &gamma, (PTPRG) is a tumor suppressor gene, down-regulated in Chronic Myeloid Leukemia (CML) cells by the hypermethylation of its promoter region. &beta, catenin (CTNNB1) is a critical regulator of Leukemic Stem Cells (LSC) maintenance and CML proliferation. This study aims to demonstrate the antagonistic regulation between &beta, catenin and PTPRG in CML cells. The specific inhibition of PTPRG increases the activation state of BCR-ABL1 and modulates the expression of the BCR-ABL1- downstream gene &beta, Catenin. PTPRG was found to be capable of dephosphorylating &beta, catenin, eventually causing its cytosolic destabilization and degradation in cells expressing PTPRG. Furthermore, we demonstrated that the increased expression of &beta, catenin in PTPRG-negative CML cell lines correlates with DNA (cytosine-5)-methyl transferase 1 (DNMT1) over-expression, which is responsible for PTPRG promoter hypermethylation, while its inhibition or down-regulation correlates with PTPRG re-expression. We finally confirmed the role of PTPRG in regulating BCR-ABL1 and &beta, catenin phosphorylation in primary human CML samples. We describe here, for the first time, the existence of a regulative loop occurring between PTPRG and &beta, catenin, whose reciprocal imbalance affects the proliferation kinetics of CML cells.

Loss of miR-15/16 is the most common genetic lesion in chronic lymphocytic leukemia (CLL), promoting overexpression of BCL2, which factors in leukemia pathogenesis. Indeed, an inhibitor of Bcl2, venetoclcax, is highly active in the treatment of patients with CLL. However, single-agent venetoclcax fails to eradicate minimal residual disease in most patients. Accordingly, we were interested in other genes that may be regulated by miR-15/16, which may target other drivers in CLL. We found that miR-15/16 targets ROR1, which encodes an onco-embryonic surface protein expressed on the CLL cells of over 90% of patients, but not on virtually all normal postpartum tissues. CLL with high-level expression of ROR1 also have high-level expression of Bcl2, but low-to-negligible miR-15/16. Moreover, CLL cases with high-level ROR1 have deletion(s) at the chromosomal location of the genes encoding miR-15/16 (13q14) more frequently than cases with low-to-negligible ROR1, implying that deletion of miR-15/16 may promote overexpression of ROR1, in addition to BCL2. ROR1 is a receptor for Wnt5a, which can promote leukemia-cell proliferation and survival, and can be targeted by cirmtuzumab, a humanized anti-ROR1 mAb. We find that this mAb can enhance the in vitro cytotoxic activity of venetoclcax for CLL cells with high-level expression of ROR1, indicating that combining these agents, which target ROR1 and Bcl2, may have additive, if not synergistic, activity in patients with this disease.

Background Protein tyrosine phosphatase receptor gamma (PTPRG) is a ubiquitously expressed member of the protein tyrosine phosphatase family known to act as a tumor suppressor gene in many different neoplasms with mechanisms of inactivation including mutations and methylation of CpG islands in the promoter region. Although a critical role in human hematopoiesis and an oncosuppressor role in chronic myeloid leukemia (CML) have been reported, only one polyclonal antibody (named chPTPRG) has been described as capable of recognizing the native antigen of this phosphatase by flow cytometry. Protein biomarkers of CML have not yet found applications in the clinic, and in this study, we have analyzed a group of newly diagnosed CML patients before and after treatment. The aim of this work was to characterize and exploit a newly developed murine monoclonal antibody specific for the PTPRG extracellular domain (named TPγ B9-2) to better define PTPRG protein downregulation in CML patients. Methods TPγ B9-2 specifically recognizes PTPRG (both human and murine) by flow cytometry, western blotting, immunoprecipitation, and immunohistochemistry. Results Co-localization experiments performed with both anti-PTPRG antibodies identified the presence of isoforms and confirmed protein downregulation at diagnosis in the Philadelphia-positive myeloid lineage (including CD34+/CD38bright/dim cells). After effective tyrosine kinase inhibitor (TKI) treatment, its expression recovered in tandem with the return of Philadelphia-negative hematopoiesis. Of note, PTPRG mRNA levels remain unchanged in tyrosine kinase inhibitors (TKI) non-responder patients, confirming that downregulation selectively occurs in primary CML cells. Conclusions The availability of this unique antibody permits its evaluation for clinical application including the support for diagnosis and follow-up of these disorders. Evaluation of PTPRG as a potential therapeutic target is also facilitated by the availability of a specific reagent capable to specifically detect its target in various experimental conditions. Electronic supplementary material The online version of this article (doi:10.1186/s13045-017-0494-z) contains supplementary material, which is available to authorized users.

Noncoding RNAs (ncRNAs) have received much attention due to their central role in gene expression and translational regulation as well as due to their involvement in several biological processes and disease development. Small noncoding RNAs (sncRNAs), such as microRNAs and piwiRNAs, have been thoroughly investigated and functionally characterized. Long noncoding RNAs (lncRNAs), known to play an important role in chromatin-interacting transcription regulation, posttranscriptional regulation, cell-to-cell signaling, and protein regulation, are also being investigated to further elucidate their functional roles.Next-generation sequencing (NGS) technologies have greatly aided in characterizing the ncRNAome. Moreover, the coupling of NGS technology together with bioinformatics tools has been essential to the genome-wide detection of RNA modifications in ncRNAs. RNA editing, a common human co-transcriptional and posttranscriptional modification, is a dynamic biological phenomenon able to alter the sequence and the structure of primary transcripts (both coding and noncoding RNAs) during the maturation process, consequently influencing the biogenesis, as well as the function, of ncRNAs. In particular, the dysregulation of the RNA editing machineries have been associated with the onset of human diseases.In this chapter we discuss the potential functions of ncRNA editing and describe the knowledge base and bioinformatics resources available to investigate such phenomenon.

MicroRNAs are a class of small noncoding RNA involved in the mechanism of RNA silencing and regulation of gene expression at a posttranscriptional level. Recently, the discovery of their targets led to the understanding of the molecular role of these small molecules and their involvement in the pathogenesis of numerous diseases, including cancer. Not long ago, the improvement of several informatics tools for microRNA target prediction has supported the experimental research through the selection of potential mRNA as microRNA target candidates. Since the regulation mediated by microRNA affects gene expression at a posttranscriptional level, the analysis of the proteins encoded by the gene targets is essential in understanding the involvement of these small molecules in biological processes and their role in several diseases. In this chapter, we describe the experimental procedure of Western blotting applied to the validation of microRNA targets. Western blotting is one of the most common and largest know technique for protein analysis. This method, coupled with the luciferase assay, represents the standard procedure for the experimental confirmation of microRNA targeting.

MicroRNAs (miRNAs) are small noncoding RNAs that are 22-25 nucleotides in length and control gene expression posttranscriptionally by degrading mRNAs or by translational repression. Many computational tools based on algorithms for target prediction have already been developed to find potential miRNA-target interactions. Since it is essential to confirm in silico predictions, experimental approaches have been improved to validate computationally predicted targets. One of the most widely used techniques is the luciferase assay which allows for the confirmation of specific binding between microRNA and the mRNA target using a reporter plasmid containing the 3' UTR of the target. Through the mutagenesis of this region it is possible to provide indirect evidence of the specific microRNA-mRNA interaction demonstrated using this assay. In this chapter we review the main experimental steps of the 3' UTR mutagenesis and the best way to apply this method to support and complete the luciferase assay procedure.

MicroRNAs (miRNAs) are small noncoding RNAs of 22-25 nucleotides that control gene expression at the posttranscriptional level through the degradation of mRNAs or translational repression. In the last 15 years, the study of these small molecules helped elucidate their role in the regulation of many cellular processes and the onset and development of several diseases. Therefore, many computational tools based on algorithms for target prediction have been developed to identify potential miRNA-target interactions. The improvement of experimental approaches to more easily and quickly confirm in silico predictions has become essential for the study of these small RNAs and their molecular functions. In this chapter, we summarized the principal steps of one of the most used techniques for the validation of microRNA targets, the Luciferase assay, thus explaining the underlying principles and the procedures to apply it best.

Chronic lymphocytic leukemia (CLL) is the most common adult leukemia. It is characterized by the accumulation of CD19+/CD5+ lymphocytes and can have variable outcomes. Richter syndrome (RS) is a lethal complication in CLL patients that results in aggressive B-cell lymphomas, and there are no tests to predict its occurrence. Because alterations in microRNA expression can predict the development and progression of several cancers, we investigated whether dysregulation of specific microRNAs can predict RS in CLL patients. Thus, we compared microRNA expression levels in samples from 49 CLL patients who later developed RS with samples from 59 CLL patients who did not. We found that high expression of miR-125a-5p or low expression of miR-34a-5p can predict ∼50% of RS with a false positive rate of ∼9%. We found that CLL patients predicted to develop RS show either an increase of miR-125a-5p expression (∼20-fold) or a decrease of miR-34a-5p expression (∼21-fold) compared with CLL patients that are not predicted to develop RS. Thus, miR-125a-5p and miR-34a-5p can be valuable predictor markers of RS and have the potential to provide physicians with information that can indicate the best therapeutic strategy for CLL patients.

Small, noncoding RNAs are short untranslated RNA molecules, some of which have been associated with cancer development. Recently we showed that a class of small RNAs generated during the maturation process of tRNAs (tRNA-derived small RNAs, hereafter “tsRNAs”) is dysregulated in cancer. Specifically, we uncovered tsRNA signatures in chronic lymphocytic leukemia and lung cancer and demonstrated that the ts-4521/3676 cluster (now called “ts-101” and “ts-53,” respectively), ts-46, and ts-47 are down-regulated in these malignancies. Furthermore, we showed that tsRNAs are similar to Piwi-interacting RNAs (piRNAs) and demonstrated that ts-101 and ts-53 can associate with PiwiL2, a protein involved in the silencing of transposons. In this study, we extended our investigation on tsRNA signatures to samples collected from patients with colon, breast, or ovarian cancer and cell lines harboring specific oncogenic mutations and representing different stages of cancer progression. We detected tsRNA signatures in all patient samples and determined that tsRNA expression is altered upon oncogene activation and during cancer staging. In addition, we generated a knocked-out cell model for ts-101 and ts-46 in HEK-293 cells and found significant differences in gene-expression patterns, with activation of genes involved in cell survival and down-regulation of genes involved in apoptosis and chromatin structure. Finally, we overexpressed ts-46 and ts-47 in two lung cancer cell lines and performed a clonogenic assay to examine their role in cell proliferation. We observed a strong inhibition of colony formation in cells overexpressing these tsRNAs compared with untreated cells, confirming that tsRNAs affect cell growth and survival.

Background: Chronic Myelocytic Leukemia (CML) is a clonal myeloproliferative disorder characterized by constitutive phosphorylation of Protein Tyrosine kinases (PTKS) that continuously activates multiple proliferative and antiapoptotic signaling pathways. Protein Tyrosine Phosphatases (PTPs) on the other hand is potential natural inhibitory mechanism for regulating the tyrosine kinase activities in which phosphorylation is reciprocally controlled and maintained in equilibrium state by PTKs and PTPs. As a member of PTPs family, Protein Tyrosine Phosphatase Receptor Gamma (PTPRG) was found to act as a tumor suppressor gene. This negative regulatory mechanism of PTPRG was observed to be down-regulated and disabled in CML and one of the possible mechanisms that alter the negative regulatory effect of PTPs is mutations. Several mutations have been identified in PTPs in many different leukemias such as Acute Myeloid Leukemia (AML), Juvenile MyeloMonocytic Leukemia (JMML), Myelodysplasic Syndrome (MDS), B-cell Acute Lymphoblastic Leukemia (B-ALL) and these mutations are associated with hyper-cellular proliferation, disease progression and poor outcome. However, relatively little is known about PTPRG mutations and no studies on CML are available in the literature while mutations inBCR-ABL1tyrosine kinase have been extensively characterized. Thus, understanding the role of PTPRG in antagonizing the PTK phosphorylation of BCR-ABL1 will be important to determine its role in CML development and progression. Aim: 1) To identify potential genetic alterations causing inactivation of PTPRG and 2) correlate the PTPRG findings with patients' response to the Tyrosine kinase Inhibitors. Methods: 16 CML patients, 9 from Qatar and 7 from Italy respectively, were studied for PTPRG mutations by exome sequencing. Custom primers were designed for Human PTPRG gene (5 Kb of exonic region of interest) using Ion AmpliSeq Designer. Target regions were enriched and amplified for the 16 DNA samples using Ion AmpliSeq Library kit 2.0. The amplicons were partially digested with FuPa reagent and phosphorylated prior to ligation of Ion Xpress Barcode Adapters followed by cleanup using HighPrep reagent. The adapter ligated molecules were enriched with adapter specific primers using a limited cycle PCR followed by a cleanup using HighPrep reagent. The final libraries were quantified on Qubit Flurometer using Qubit dsDNA HS Assay Kit and Agilent Bioanalyzer using Agilent High Sensitivity DNA Kit. All samples were pooled according to the concentrations on the Bioanalyzer and loaded on Ion 318TM Chip kit V2 to be sequenced on Ion Personal Genome Machine (PGM) system. European Leukemia Net (ELN) 2013 criteria were employed to assess the response/resistance of patients to treatment. Responses are defined at the hematological, cytogenetic and molecular levels. Patients response was classified into optimal and failure Results: Four mutations/variants were identified in PTPRG genes, three were missense Y92H, G574S, S561Y and 1 was frameshift Y285fs in the 16 CML patients. PTPRG Y92H was identified in 5 (1 Homozygous and 4 heterozygous alleles) patients and the 5 patient failed the Imatinib Mesylate (IM) treatment. On the other hand, The PTPRG G574S was identified in 6 (2 homozygous and 4 heterozygous alleles) patients. Out of the 6 patients, 4 were classified as failure to the treatment and 2 responded optimally. In addition, the PTPRG S561Y and Y285fs were identified on 1 and 3 patients respectively and these patients responded optimally to IM treatment. Discussion and Conclusions: This is the first prospective pilot study to investigate PTPRG gene mutations as underlying mechanism to explain treatment failure. Our preliminary data showed that the identified variant PTPRG Y92H might be associated with IM failure although it has been reported as Single Nucleotide Polymorphisms (SNPs) (rs62620047) and this could be attributed that some polymorphisms might behave like a mutation. On the other hand, PTPRG G574S variant (rs2292245) showed various clinical outcomes regardless to its allele zygosity as 67% (4/6) of patients failed the TKIs treatment. From the results of our pilot study we recommend carrying out PTPRG sequencing in a significantly larger cohort of patients to further explore and pinpoint the crucial mutations that can be correlated with CML resistance/response to treatment. Disclosures No relevant conflicts of interest to declare.