Search

Objective 3' tRNA-derived fragments (3' tRFs) are important epigenetic regulators in normal and pathological conditions. In this study, we aimed to explore the potential value of a 3' tRF as a prognostic and/or screening biomarker for B-cell chronic lymphocytic leukemia (B-CLL). Methods Publicly available next-generation sequencing data from 20 B-CLL cases were analyzed, followed by prediction of targets of the most abundantly and ubiquitously expressed 3' tRFs, leading to selection of tRF-LeuAAG/TAG . PBMCs were isolated from blood samples of 91 B-CLL patients and 43 non-leukemic donors, followed by total RNA extraction, in-vitro polyadenylation, and first-strand cDNA synthesis. Next, a real-time quantitative PCR (qPCR) assay was developed for the accurate quantification of tRF-LeuAAG/TAG and applied in all samples, prior to biostatistical analysis. Results High tRF-LeuAAG/TAG levels are associated with inferior overall survival (OS) of B-CLL patients. The unfavorable significance of tRF-LeuAAG/TAG was independent of established prognostic factors in B-CLL. Stratified Kaplan-Meier OS analysis uncovered the unfavorable prognostic role of high tRF-LeuAAG/TAG levels for patients in Binet A or Rai I stage, negative CD38 expression, mutated, or unmutated IGHV genomic locus. Conclusion Our approach revealed the independent prognostic value of a particular 3' tRF, derived from tRNALeuAAG and tRNALeuTAG (tRF-LeuAAG/TAG ) in B-CLL.

MicroRNAs are small non-coding RNAs that act at the post-transcriptional level, regulating protein expression by repressing translation or destabilizing mRNA target. Because of their discovery, microRNAs have been associated with almost every normal cell function, including proliferation, differentiation and apoptosis. Several lines of evidence suggest that they have an important role in normal hematopoiesis as exemplified by the role of mir-155 and mir-150 in the differentiation of B and T lymphocytes, the suppressive role of mir-221 and mir-222 in erythroid differentiation, the inhibitory effect of mir-181 on hematopoietic differentiation and the induction of myeloid differentiation by mir-223. Moreover, they play a role both as oncogenes, probably by a variety of mechanisms, namely through elimination of tumor suppressor proteins, or as tumor suppressor genes by targeting oncogenic mRNAs. Their aberrant expression has been associated with solid tumors and hematopoietic malignancies as suggested by the frequent deletion of mir-15a and mir-16-1 in chronic lymphocytic leukemia, the increased levels of mir-155 in diffuse large B-cell lymphomas and the increased levels of mir-181 in acute myeloid leukemia M1 and M2. The purpose of this review is to summarize current knowledge on the role of microRNAs in normal hematopoiesis and hematopoietic malignancies and, moreover, to highlight their role as potential therapeutic tools.

Myelodysplastic syndromes (MDS) represent a group of clonal hematopoietic disorders characterized by dyshemopoiesis and frequent evolution to acute leukemia. Tumor suppressor gene inactivation may be involved in MDS pathogenesis. The two families of cyclin-dependent kinase inhibitors (CDKIs) (INK4 family of p15, p16, p18 and p19 and CIP/KIP family of p21, p27 and p57) that negatively regulate cell cycle progression are known tumor suppressor genes. To determine whether genetic alterations of p16 and p27 genes play an important role in MDS pathogenesis, we examined DNA from 51 patients classified as 17 refractory anemias (RA), four refractory anemias with ringed sideroblasts (RARS), 19 refractory anemias with an excess of blasts (RAEB), 5 refractory anemias with excess of blasts in transformation (RAEB-t) and 6 chronic myelomonocytic leukemias (CMML). Southern blot analysis detected no homozygous deletions of p16 and p27. Polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) and sequencing did not reveal point mutations for both genes with the exception of two allelic polymorphisms, namely a C --> G transition at 447 bp of p16exon3 and a T --> A transition at 791 bp of p27exon1 genes. Our results suggest that mutations of p16 and p27 genes resulting in abnormal p16 and p27 proteins do not represent a mechanism of gene inactivation involved in the pathogenesis of MDS.

Objectives: Chronic lymphocytic leukemia (CLL) comprises a heterogenous group of at least two types of disease entities characterized by distinctive clinical, immunophenotypical and genetic features. The molecular mechanisms underlying the pathogenesis and the histological transformation of CLL are not well known. The INK4A/p16, a cyclin dependent kinase inhibitor has been considered as a tumor suppressor gene. Inactivation of this gene by homozygous deletions, mutations and hypermethylation occurs in a variety of human neoplasms. The aim of the present study was to determine the frequency of p16 gene deletions and mutations as well as the methylation status of the same gene in CLL patients. Methods: We examined 34 samples from CLL patients by Southern Blotting, Single-Strand Conformation Polymorphism (SSCP), DNA sequencing and Methylation-Specific PCR. Results: Southern Blot analysis revealed non-rearranged bands in 33/34 cases. Homozygous deletions were not observed in any case. In 1/34 case a rearranged band was detected with EcoRI enzyme. The PCR-SSCP analysis of exons 1 and 3 revealed normal pattern of migration in all cases examined. The analysis of exon 2 revealed abnormal migration pattern in 2/34 cases (5.8%). Sequencing of these cases revealed the presence of the ALA148THR polymorphism. Methylation analysis of p16 gene promoter revealed hypermethylation of CpG islands in 6/34 cases (17.6%). Conclusion: These results indicate that genetic alterations of p16 gene are rare events in patients with CLL. The clarification of the role of p16 gene promoter methylation in the pathogenesis and evolution of CLL needs further investigation.