Background/Aims: The degradation of mRNA is a key process in the control of gene expression correlated to anomalous cell proliferation. The rate-limiting step of mRNA degradation is the removal of the poly(A) tail by deadenylases. However, studies on deadenylase expression in cancer are limited. Herein, we analyzed the expression of several deadenylases from acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML). Methods: Clinical samples from patients diagnosed with ALL and AML were the source of leukemic cells. Extracts from leukemic and control cells were analyzed for deadenylase mRNA levels using qRT-PCR, and the protein levels of PARN and CNOT7 deadenylases using immunoblotting. Results: RT-PCR analysis revealed altered expression for CNOT6, CNOT6L, CNOT7 and PARN deadenylases. The most significant alterations were observed for PARN and CNOT7 mRNA levels, which also reflect on the cognate protein level. Further analysis revealed that a significant amount of PARN is phosphorylated in ALL. Conclusions: We show that the expression of several deadenylases in acute leukemias is altered. The increase of PARN expression and the alteration of its phosphorylation status indicate important regulatory events. These data suggest that the role of deadenylases as auxiliary biomarkers and therapeutic targets should be meticulously investigated.

Lung cancer is the leading cause of cancer mortality worldwide, mainly due to late diagnosis, poor prognosis and tumor heterogeneity. Thus, the need for biomarkers that will aid classification, treatment and monitoring remains intense and challenging and depends on the better understanding of the tumor pathobiology and underlying mechanisms. The deregulation of gene expression is a hallmark of cancer and a critical parameter is the stability of mRNAs that may lead to increased oncogene and/or decreased tumor suppressor transcript and protein levels. The shortening of mRNA poly(A) tails determines mRNA stability, as it is usually the first step in mRNA degradation, and is catalyzed by deadenylases. Herein, we assess the clinical significance of deadenylases and we study their role on gene expression in squamous cell lung carcinoma (SCC). Computational transcriptomic analysis from a publicly available microarray was performed in order to examine the expression of deadenylases in SCC patient samples. Subsequently we employed real-time PCR in clinical samples in order to validate the bioinformatics results regarding the gene expression of deadenylases. Selected deadenylases were silenced in NCI-H520 and Hep2 human cancer cell lines and the effect on gene expression was analyzed with cDNA microarrays. The in silico analysis revealed that the expression of several deadenylases is altered in SCC. Quantitative real-time PCR showed that four deadenylases, PARN, CNOT6, CNOT7 and NOC, are differentially expressed in our SCC clinical samples. PARN overexpression correlated with younger patient age and CNOT6 overexpression with non-metastatic tumors. Kaplan-Meier analysis suggests that increased levels of PARN and NOC correlate with significantly increased survival. Gene expression analysis upon PARN and NOC silencing in lung cancer cells revealed gene expression deregulation that was functionally enriched for gene ontologies related to cell adhesion, cell junction, muscle contraction and metabolism. Our results highlight the clinical significance of PARN and NOC on the survival in SCC diagnosed patients. We demonstrate that the enzymes are implicated in important phenotypes pertinent to cancer biology and provide information on their role in the regulation of gene expression in SCC. Overall, our results support an emerging role for deadenylases in SCC and contribute to the understanding of their role in cancer biology.

Background: Interleukin-27 (IL-27) has been proposed to be useful for diagnosing tuberculous pleural effusion (TPE). Adenosine deaminase (ADA) has been long used for the same purpose. The aim of this study was to compare the performance of IL-27, ADA, and their product (IL-27•ADA) in the diagnosis of TPE. Methods: Pleural fluid samples from patients with exudative pleural effusions were assessed for IL-27 and ADA levels. Receiver operating characteristic (ROC) curves were constructed to compare the overall diagnostic accuracy of IL-27, ADA, and IL-27•ADA. Curves of false-positive (FPR) and false-negative (FNR) rates as a function of TPE prevalence were also constructed, and mean rates of false results in low (1–10%), intermediate (11–40%), and high (41–70%) prevalences were estimated to evaluate the ability of the three markers in ruling in or ruling out TPE. Results: We studied 121 exudates. IL-27 and ADA were higher in TPEs compared with non-TPEs and they presented similar accuracies for the diagnosis of TPE. The product of IL-27 and ADA (IL-27•ADA) was more accurate than ADA for the same purpose. IL-27 and IL-27•ADA presented the lowest overall FPR and FNR, respectively. The FPR of IL-27, ADA and IL-27•ADA was > 9%, even in high prevalence settings. Although their FNR was < 2% in low prevalence settings, only IL-27•ADA exhibited sufficiently low FNR (< 1%) in intermediate and high prevalences. Conclusions: ADA, IL-27, and IL-27•ADA cannot reliably ‘rule in’ TPE in any prevalence setting. TPE can be ‘ruled out’ by each of the biomarkers in low prevalence settings. In intermediate and high prevalence settings, IL-27•ADA is a reliable ‘rule out’ test in the diagnostic approach to TPEs.

Deadenylation is the exoribonucleolytic shortening of eukaryotic poly(A) tails. It is often the first and rate-limiting step for mRNA decay and translational silencing. The process is catalysed by a diversity of deadenylases, which provide robust and flexible means to control mRNA levels and gene expression. Poly(A)-specific ribonuclease (PARN) is a major mammalian deadenylase and the only known to concurrently bind the 5' cap-structure and the 3' poly(A), thus enhancing the degradation rate and amplifying its processivity. PARN is important during oocyte maturation, embryogenesis, early development, DNA damage, and in cell-cycle progression, but also in processes beyond mRNA metabolism, such as the maturation of snoRNAs. The enzyme also participates in nonsense-mediated mRNA decay and in the regulation of cytoplasmic polyadenylation. Importantly, PARN is involved in the degradation of several cancerrelated genes, while its expression is altered in cancer. Apart from the direct interaction with the cap structure, several strategies regulate PARN activity, such as phosphorylation, interaction with RNA-binding proteins (RBPs), and natural nucleotides. Recent studies have focused on the regulation of its activity by synthetic nucleoside analogues with therapeutic potential. In this context, the wide repertoire of RBPs and molecules that regulate PARN activity, together with the established role of deadenylases in miRNA-mediated regulation of mRNA expression, suggest that mRNA turnover is more complex than it was previously thought and PARN holds a key role in this process. In this review, we highlight the importance of PARN during RNA’s lifecycle and discuss clinical perspectives of modulating its activity.