Dyskerin and TERC expression may condition survival in lung cancer patients

Advancements in pseudouridine modifying enzyme and cancer

Pseudouridine (Ψ) is a post-transcriptional modifier of RNA, often referred to as the 'fifth nucleotide' owing to its regulatory role in various biological functions as well as because of its significant involvement in the pathogenesis of human cancer. In recent years, research has revealed various Ψ modifications in different RNA types, including messenger RNA, transfer RNA, ribosomal RNA, small nuclear RNA, and long noncoding RNA. Pseudouridylation can significantly alter RNA structure and thermodynamic stability, as the Ψ-adenine (A) base pair is more stable than the typical uridine (U)-A base pair is due to its structural similarity to adenine. Studies have linked Ψ expression to the development and progression of several digestive system cancers, such as liver cancer and colorectal cancer, and nondigestive system cancers, such as breast cancer, non-small cell lung cancer, prostate cancer, glioblastoma, ovarian cancer, oral squamous cell carcinoma, and pituitary cancer. The present review briefly outlines the chemical structure, synthesis, and regulatory mechanisms of Ψ. This review summarizes the effects of pseudouridylation on various substrates of RNA and briefly discusses methods for detecting Ψ. Last, it focuses on how RNA pseudouridylation influences different cancers, emphasizing the search for novel approaches to cancer diagnosis, treatment, and prognosis through Ψ modification.

Implications of RNA pseudouridylation for cancer biology and therapeutics: a narrative review

BACKGROUND

Pseudouridine (Ψ), a C5-glycoside isomer of uridine, stands as one of the most prevalent RNA modifications in all RNA types. Distinguishing from the C-N bond linking uridine to ribose, the link between Ψ and ribose is a C-C bond, endowing Ψ modified RNA distinct properties and functions in various biological processes. The conversion of uridine to Ψ is governed by pseudouridine synthases (PUSs). RNA pseudouridylation is implicated in cancer biology and therapeutics.

OBJECTIVES

In this review, we will summarize the methods for detecting Ψ, the process of Ψ generation, the impact of Ψ modification on RNA metabolism and gene expression, the roles of dysregulated Ψ and pseudouridine synthases in cancers, and the underlying mechanism.

METHODS

We conducted a comprehensive search of PubMed from its inception through February 2024. The search terms included "pseudouridine"; "pseudouridine synthase"; "PUS"; "dyskerin"; "cancer"; "tumor"; "carcinoma"; "malignancy"; "tumorigenesis"; "biomarker"; "prognosis" and "therapy". We included studies published in peer-reviewed journals that focused on Ψ detection, specific mechanisms involving Ψ and PUSs, and prognosis in cancer patients with high Ψ expression. We excluded studies lacking sufficient methodological details or appropriate controls.

RESULTS

Ψ has been recognized as a significant biomarker in cancer diagnosis and prognosis. Abnormal Ψ modifications mediated by various PUSs result in dysregulated RNA metabolism and impaired RNA function, promoting the development of various cancers. Overexpression of PUSs is common in cancer cells and predicts poor prognosis. PUSs inhibition arrests cell proliferation and enhances apoptosis in cancer cells, suggesting PUS-targeting cancer therapy may be a potential strategy in cancer treatment.

DISCUSSION

High Ψ levels in serum, urine, and saliva may suggest cancer, but do not specify the type, requiring additional lab markers and imaging for accurate diagnosis. Standardized detection methods are also crucial for reliable results. PUSs are linked to cancer, but more researches are needed to understand their mechanisms in different cancers. Anticancer treatments targeting PUSs are still under developed.

Decoding the 'Fifth' Nucleotide: Impact of RNA Pseudouridylation on Gene Expression and Human Disease

Cellular RNAs, both coding and noncoding are adorned by > 100 chemical modifications, which impact various facets of RNA metabolism and gene expression. Very often derailments in these modifications are associated with a plethora of human diseases. One of the most oldest of such modification is pseudouridylation of RNA, wherein uridine is converted to a pseudouridine (Ψ) via an isomerization reaction. When discovered, Ψ was referred to as the 'fifth nucleotide' and is chemically distinct from uridine and any other known nucleotides. Experimental evidence accumulated over the past six decades, coupled together with the recent technological advances in pseudouridine detection, suggest the presence of pseudouridine on messenger RNA, as well as on diverse classes of non-coding RNA in human cells. RNA pseudouridylation has widespread effects on cellular RNA metabolism and gene expression, primarily via stabilizing RNA conformations and destabilizing interactions with RNA-binding proteins. However, much remains to be understood about the RNA targets and their recognition by the pseudouridylation machinery, the regulation of RNA pseudouridylation, and its crosstalk with other RNA modifications and gene regulatory processes. In this review, we summarize the mechanism and molecular machinery involved in depositing pseudouridine on target RNAs, molecular functions of RNA pseudouridylation, tools to detect pseudouridines, the role of RNA pseudouridylation in human diseases like cancer, and finally, the potential of pseudouridine to serve as a biomarker and as an attractive therapeutic target.

Molecular mechanisms underlying the regulation of tumour suppressor genes in lung cancer

Tumour suppressor genes play a cardinal role in the development of a large array of human cancers, including lung cancer, which is one of the most frequently diagnosed cancers worldwide. Therefore, extensive studies have been committed to deciphering the underlying mechanisms of alterations of tumour suppressor genes in governing tumourigenesis, as well as resistance to cancer therapies. In spite of the encouraging clinical outcomes demonstrated by lung cancer patients on initial treatment, the subsequent unresponsiveness to first-line treatments manifested by virtually all the patients is inherently a contentious issue. In light of the aforementioned concerns, this review compiles the current knowledge on the molecular mechanisms of some of the tumour suppressor genes implicated in lung cancer that are either frequently mutated and/or are located on the chromosomal arms having high LOH rates (1p, 3p, 9p, 10q, 13q, and 17p). Our study identifies specific genomic loci prone to LOH, revealing a recurrent pattern in lung cancer cases. These loci, including 3p14.2 (FHIT), 9p21.3 (p16INK4a), 10q23 (PTEN), 17p13 (TP53), exhibit a higher susceptibility to LOH due to environmental factors such as exposure to DNA-damaging agents (carcinogens in cigarette smoke) and genetic factors such as chromosomal instability, genetic mutations, DNA replication errors, and genetic predisposition. Furthermore, this review summarizes the current treatment landscape and advancements for lung cancers, including the challenges and endeavours to overcome it. This review envisages inspired researchers to embark on a journey of discovery to add to the list of what was known in hopes of prompting the development of effective therapeutic strategies for lung cancer.

Viral and cellular telomerase RNAs possess host-specific anti-apoptotic functions

Human telomerase RNA (hTR) is overexpressed in many cancers and protects T cells from apoptosis in a telomerase-independent manner. The most prevalent cancer in the animal kingdom is caused by the highly oncogenic herpesvirus Marek's disease virus (MDV). MDV encodes a viral telomerase RNA (vTR) that plays a crucial role in MDV-induced tumorigenesis and shares all four conserved functional domains with hTR. In this study, we assessed whether hTR drives tumor formation in this natural model of herpesvirus-induced tumorigenesis. Therefore, we replaced vTR with hTR in the genome of a highly oncogenic MDV. Furthermore, we investigated the anti-apoptotic activity of vTR, hTR, and their counterpart in the chicken [chicken telomerase RNA (cTR)]. hTR was efficiently expressed and did not alter replication of the recombinant virus. Despite its conserved structure, hTR did not complement the loss of vTR in virus-induced tumorigenesis. Strikingly, hTR did not inhibit apoptosis in chicken cells, but efficiently inhibited apoptosis in human cells. Inverse host restriction has been observed for vTR and cTR in human cells. Our data revealed that vTR, cTR, and hTR possess conserved but host-specific anti-apoptotic functions that likely contribute to MDV-induced tumorigenesis. IMPORTANCE hTR is overexpressed in many cancers and used as a cancer biomarker. However, the contribution of hTR to tumorigenesis remains elusive. In this study, we assessed the tumor-promoting properties of hTR using a natural virus/host model of herpesvirus-induced tumorigenesis. This avian herpesvirus encodes a telomerase RNA subunit (vTR) that plays a crucial role in viral tumorigenesis and shares all conserved functional domains with hTR. Our data revealed that vTR and cellular TRs of humans and chickens possess host-specific anti-apoptotic functions. This provides important translational insights into therapeutic strategies, as inhibition of apoptosis is crucial for tumorigenesis.

RNA modification: mechanisms and therapeutic targets

RNA modifications are dynamic and reversible chemical modifications on substrate RNA that are regulated by specific modifying enzymes. They play important roles in the regulation of many biological processes in various diseases, such as the development of cancer and other diseases. With the help of advanced sequencing technologies, the role of RNA modifications has caught increasing attention in human diseases in scientific research. In this review, we briefly summarized the basic mechanisms of several common RNA modifications, including m6A, m5C, m1A, m7G, Ψ, A-to-I editing and ac4C. Importantly, we discussed their potential functions in human diseases, including cancer, neurological disorders, cardiovascular diseases, metabolic diseases, genetic and developmental diseases, as well as immune disorders. Through the "writing-erasing-reading" mechanisms, RNA modifications regulate the stability, translation, and localization of pivotal disease-related mRNAs to manipulate disease development. Moreover, we also highlighted in this review all currently available RNA-modifier-targeting small molecular inhibitors or activators, most of which are designed against m6A-related enzymes, such as METTL3, FTO and ALKBH5. This review provides clues for potential clinical therapy as well as future study directions in the RNA modification field. More in-depth studies on RNA modifications, their roles in human diseases and further development of their inhibitors or activators are needed for a thorough understanding of epitranscriptomics as well as diagnosis, treatment, and prognosis of human diseases.

Dyskerin and telomerase RNA component are sex-differentially associated with outcomes and Sunitinib response in patients with clear cell renal cell carcinoma

BACKGROUND

Clear cell renal cell carcinoma (ccRCC) displays sex-biased incidence, outcomes, molecular alterations and treatment efficacy; however, clinical managements are largely identical in male and female patients. Moreover, many biomarkers have been identified as predictors for ccRCC outcomes and response to therapeutic drugs, such as multitargeted tyrosine-kinase receptor (TKR) inhibitors, but little is known about their sex-specificity. Dyskerin (DKC1), encoded by the DKC1 gene within Xq28, is a telomerase co-factor stabilizing telomerase RNA component (TERC) and overexpressed in various cancers. Here, we determined whether DKC1 and/or TERC affect ccRCC sex-differentially.

METHODS

DKC1 and TERC expression in primary ccRCC tumors was assessed using RNA sequencing and qPCR. DKC1 association with molecular alterations and overall or progression-free survival (OS or PFS) was analyzed in the TCGA cohort of ccRCC. The IMmotion 151 and 150 ccRCC cohorts were analyzed to evaluate impacts of DKC1 and TERC on Sunitinib response and PFS.

RESULTS

DKC1 and TERC expression was significantly upregulated in ccRCC tumors. High DKC1 expression predicts shorter PFS independently in female but not male patients. Tumors in the female DKC1-high group exhibited more frequent alterations in PIK3CA, MYC and TP53 genes. Analyses of the IMmotion 151 ccRCC cohort treated with the TKR inhibitor Sunitinib showed that female patients in the DKC1-high group was significantly associated with lower response rates (P = 0.021) accompanied by markedly shortened PFS (6.1 vs 14.2 months, P = 0.004). DKC1 and TERC expression correlated positively with each other, and higher TERC expression predicted poor Sunitinib response (P = 0.031) and shorter PFS (P = 0.004), too. However, DKC1 rather than TERC acted as an independent predictor (P < 0.001, HR = 2.0, 95% CI 1.480-2.704). In male patients, DKC1 expression was associated with neither Sunitinib response (P = 0.131) nor PFS (P = 0.184), while higher TERC levels did not predict response rates. Similar results were obtained from the analysis of the Sunitinib-treated IMmotion 150 ccRCC patients.

CONCLUSIONS

DKC1 serves as an independent female-specific predictor for survival and Sunitinib efficacy in ccRCC, which contribute to better understanding of the sex-biased ccRCC pathogenesis and improve personalized interventions of ccRCC.

Higher expression of pseudouridine synthase 7 promotes non-small cell lung cancer progression and suggests a poor prognosis

BACKGROUND

Lung cancer is currently the second most common cancer, and non-small cell lung cancer accounts for about 85% of cases. NSCLC has not been studied for pseudouridine synthase 7 (PUS), a member of the PUS family that is associated with cancer development. Here, we focused on the role and clinical significance of PUS7 in non-small cell lung cancer.

AIM

To explore the role of PUS7 in NSCLC and its clinical significance.

METHODS

We downloaded datasets from the TCGA database and CPTAC database. In normal bronchial epithelial cells as well as NSCLC cell lines, RT-PCR and Western blot were used to quantify PUS7 expression. The role of PUS7 in NSCLC has been investigated by CCK8, migration assay, migration assay, and flow cytometry. PUS7 expression in tumor tissues was detected by immunohistochemical staining, and we evaluated the influence of PUS7 expression on the prognosis of NSCLC patients after surgery using Cox regression analysis, both univariate and multivariate.

RESULTS

NSCLC cell lines and tissues expressed high levels of PUS7, and PUS7 was found to influence the proliferation, migration, and invasion of cancer cells without affecting their apoptosis. There was a worse prognosis for NSCLC patients who have higher PUS7 expression, suggesting that PUS7 was an independent indicator of prognosis (P = .05).

Research Progress of RNA Methylation Modification in Colorectal Cancer

Accumulating evidence indicates that RNA methylation, as the most common modification of mRNA, is of great significance in tumor progression and metastasis. Colorectal cancer is a common malignant tumor of the digestive system that seriously affects the health of middle-aged and elderly people. Although there have been many studies on the biological mechanism of the occurrence and development of colorectal cancer, there are still major deficiencies in the diagnosis and prognosis of colorectal cancer. With the deep study of RNA methylation, it was found that RNA modification is highly related to colorectal cancer tumorigenesis, development and prognosis. Here, we will highlight various RNA chemical modifications including N6-methyladenosine, 5-methylcytosine, N1-methyladenosine, 7-methylguanine, pseudouridine and their modification enzymes followed by summarizing their functions in colorectal cancer.

Quantifying telomeric lncRNAs using PNA-labelled RNA-Flow FISH (RNA-Flow)

Here we present a method to detect and quantify long non-coding RNAs, in particular those related to telomeres. By coupling the specificity of a peptide nucleic acid (PNA) probe with flow cytometry we have quantified cellular levels of TERRA and TERC lncRNAs in culture cell lines and PBMCs. This easy-to-use method appointed RNA-Flow allows reliable lncRNA quantification with broad applications in basic research and clinical diagnostics. In addition, the staining protocol presented here was proven useful for the detection and quantification of such lncRNAs on unfixed cells using confocal microscopy.

Telomeric-associated long non-coding RNAs TERRA and TERC can be quantified in culture cell lines and human PBMCs using peptide nucleic acid probes with flow cytometry (RNA-Flow).

Role of main RNA modifications in cancer: N6-methyladenosine, 5-methylcytosine, and pseudouridine

Cancer is one of the major diseases threatening human life and health worldwide. Epigenetic modification refers to heritable changes in the genetic material without any changes in the nucleic acid sequence and results in heritable phenotypic changes. Epigenetic modifications regulate many biological processes, such as growth, aging, and various diseases, including cancer. With the advancement of next-generation sequencing technology, the role of RNA modifications in cancer progression has become increasingly prominent and is a hot spot in scientific research. This review studied several common RNA modifications, such as N⁶-methyladenosine, 5-methylcytosine, and pseudouridine. The deposition and roles of these modifications in coding and noncoding RNAs are summarized in detail. Based on the RNA modification background, this review summarized the expression, function, and underlying molecular mechanism of these modifications and their regulators in cancer and further discussed the role of some existing small-molecule inhibitors. More in-depth studies on RNA modification and cancer are needed to broaden the understanding of epigenetics and cancer diagnosis, treatment, and prognosis.

Evaluation of dyskerin expression and the Cajal body protein WRAP53β as potential prognostic markers for patients with primary vaginal carcinoma

Primary vaginal cancer (PVC) is a rare gynaecological malignancy, which, at present, lacks appropriate biomarkers for prognosis. The proteins dyskerin and WD repeat containing antisense to TP53 (WRAP53β), both of which exert their functions in the telomerase holoenzyme complex, have been shown to be upregulated in different cancer types. These proteins have also been proposed as prognostic markers in some types of cancer. The aim of the present study was to examine the expression patterns of dyskerin and WRAP53β in patients with PVC. Moreover, as part of a search for effective biomarkers to evaluate prognosis in PVC, the expression of these two proteins and their potential association with clinical variables and survival were also evaluated. The expression of dyskerin and WRAP53β was assessed in PVC tumour samples from 68 patients using immunohistochemistry. The majority of tumour samples showed low and moderate expression levels of dyskerin. Upregulation of dyskerin in tumour samples was significantly associated with a shorter survival time and a poorer cancer-specific survival rate. WRAP53β was also expressed in most of the cells but was not significantly associated with clinical variables or survival. This study demonstrates that upregulation of dyskerin is significantly associated with poor prognosis. Thus, dyskerin may serve as a promising prognostic marker and a potential putative therapeutic target in PVC.

Accuracy of 18F-FDG in Detecting Stage I Lung Adenocarcinomas According to IASLC/ATS/ERS Classification

BACKGROUND

Only a small number of studies have explored the clinicopathological features of pulmonary adenocarcinoma (PA) associated with 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) false-negative (FN) results. Herein, we investigated the FDG-PET diagnostic performance by stratifying PAs according to International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society/American Thoracic Society/European Respiratory Society (IASLC/ATS/ERS) classification.

METHODS

From January 2002 to December 2016, all consecutive patients who underwent pulmonary resection for stage I PA at six thoracic surgery institutions were retrospectively reviewed. The diagnostic performance of FDG-PET was analysed according to IASLC/ATS/ERS classification and two validated subclassifications. Univariable and multivariable logistic analysis were used to identify predictors of FDG-PET FN results.

RESULTS

Five hundred and fifty (550) patients with stage I PA were included in the analyses. Most of the patients were male (n=354 [64.4%]) and smokers (n=369 [67.1%]). Ninety-seven (n=97 [17.6%]) FN cases were observed at FDG-PET imaging. On multivariable analysis, a lepidic pattern was found to be independently associated with FDG-PET FN results (odds ratio [OR], 3.20; p<0.001), while a solid pattern more commonly presented with a positive finding (OR, 0.40; p=0.066). According to Nakamura's classification, we observed an independent association between lepidic pattern and FDG-PET FN results (OR, 3.17; p<0.001), while solid/micropapillary patterns were independently related with increased FDG uptake (OR, 0.35; p=0.021). According to Yoshizawa's classification, Intermediate-grade tumours were independently correlated with FN FDG-PET results (OR, 2.78; p=0.005).

CONCLUSIONS

In our cohort, histopathological features were significantly associated with FDG uptake. In particular, some adenocarcinoma subtypes (mostly Lepidic pattern) have a tendency towards FN FDG-PET findings. The correlation between computed tomography findings, clinical characteristics, and FDG uptake is mandatory, in order to tailor the precise diagnostic and therapeutic pathway for each patient.

Towards a druggable epitranscriptome: Compounds that target RNA modifications in cancer

Epitranscriptomics is an exciting emerging area that studies biochemical modifications of RNA. The field has been opened up by the technical efforts of the last decade to characterize and quantify RNA modifications, and this has led to a map of post-transcriptional RNA marks in normal cell fate and development. However, the scientific interest has been fuelled by the discovery of aberrant epitranscriptomes associated with human diseases, mainly cancer. The challenge is now to see whether epitrancriptomics offers mechanisms that can be effectively targeted by low MW compounds and are thus druggable. In this review, we will describe the principal RNA modifications (with a focus on mRNA), summarize the latest scientific evidence of their dysregulation in cancer and provide an overview of the state-of-the-art drug discovery to target the epitranscriptome. Finally, we will discuss the principal challenges in the field of chemical biology and drug development to increase the potential of targeted-RNA for clinical benefit.

The non-coding epitranscriptome in cancer

Post-synthesis modification of biomolecules is an efficient way of regulating and optimizing their functions. The human epitranscriptome includes a variety of more than 100 modifications known to exist in all RNA subtypes. Modifications of non-coding RNAs are particularly interesting since they can directly affect their structure, stability, interaction and function. Indeed, non-coding RNAs such as tRNA and rRNA are the most modified RNA species in eukaryotic cells. In the last 20 years, new functions of non-coding RNAs have been discovered and their involvement in human disease, including cancer, became clear. In this review, we will present the evidence connecting modifications of different non-coding RNA subtypes and their role in cancer.

The role of m6A, m5C and Ψ RNA modifications in cancer: Novel therapeutic opportunities

RNA modifications have recently emerged as critical posttranscriptional regulators of gene expression programmes. Significant advances have been made in understanding the functional role of RNA modifications in regulating coding and non-coding RNA processing and function, which in turn thoroughly shape distinct gene expression programmes. They affect diverse biological processes, and the correct deposition of many of these modifications is required for normal development. Alterations of their deposition are implicated in several diseases, including cancer. In this Review, we focus on the occurrence of N⁶-methyladenosine (m⁶A), 5-methylcytosine (m⁵C) and pseudouridine (Ψ) in coding and non-coding RNAs and describe their physiopathological role in cancer. We will highlight the latest insights into the mechanisms of how these posttranscriptional modifications influence tumour development, maintenance, and progression. Finally, we will summarize the latest advances on the development of small molecule inhibitors that target specific writers or erasers to rewind the epitranscriptome of a cancer cell and their therapeutic potential.

Editing and Chemical Modifications on Non-Coding RNAs in Cancer: A New Tale with Clinical Significance

Currently, for seemingly every type of cancer, dysregulated levels of non-coding RNAs (ncRNAs) are reported and non-coding transcripts are expected to be the next class of diagnostic and therapeutic tools in oncology. Recently, alterations to the ncRNAs transcriptome have emerged as a novel hallmark of cancer. Historically, ncRNAs were characterized mainly as regulators and little attention was paid to the mechanisms that regulate them. The role of modifications, which can control the function of ncRNAs post-transcriptionally, only recently began to emerge. Typically, these modifications can be divided into reversible (i.e., chemical modifications: m⁵C, hm⁵C, m⁶A, m¹A, and pseudouridine) and non-reversible (i.e., editing: ADAR dependent, APOBEC dependent and ADAR/APOBEC independent). The first research papers showed that levels of these modifications are altered in cancer and can be part of the tumorigenic process. Hence, the aim of this review paper is to describe the most common regulatory modifications (editing and chemical modifications) of the traditionally considered “non-functional” ncRNAs (i.e., microRNAs, long non-coding RNAs and circular RNAs) in the context of malignant disease. We consider that only by understanding this extra regulatory layer it is possible to translate the knowledge about ncRNAs and their modifications into clinical practice.

LncRNA MEG3 inhibits non-small cell lung cancer via interaction with DKC1 protein

Long non-coding RNA (lncRNA) MEG3 is a key biomarker and therapeutic target in lung cancer; however, its underlying molecular mechanism in lung cancer progression remains unclear. The present study demonstrated a novel regulatory axis in lung cancer, lncRNA MEG3/dyskeratosis congenita 1 (DKC1), and further investigated the effects and molecular mechanism of lncRNA MEG3/DKC1 in lung cancer. RT-qPCR and western blot analysis were performed to determine gene and protein expression levels. The RNA immunoprecipitation assay was performed to verify binding between lncRNA MEG3 and DKC1. Flow cytometry analysis was performed to assess cell apoptosis, while the Cell Counting Kit-8 assay was performed to determine cell viability. Transwell and wound healing assays were performed to assess cell invasion and migration, respectively. Telomerase activity was measured using the quantitative TeloTAGGG Telomerase PCR-ELISA kit. The results demonstrated that lncRNA MEG3 was downregulated, while its binding protein, DKC1, was upregulated in lung cancer cells. Furthermore, lncRNA MEG3 inhibited cell proliferation, migration, invasion and telomerase activity in A549 cells by downregulating DKC1. lncRNA MEG3 inhibited non-small cell lung cancer progression by inhibiting telomere function, cell proliferation, telomerase activity, cell migration and invasion via regulation of the DKC1 protein expression. LncRNA MEG3/DKC1 was identified as a novel dual-directional regulatory axis in the present study, acting as a promising target for the treatment of lung cancer.

Role of RNA modifications in cancer

Specific chemical modifications of biological molecules are an efficient way of regulating molecular function, and a plethora of downstream signalling pathways are influenced by the modification of DNA and proteins. Many of the enzymes responsible for regulating protein and DNA modifications are targets of current cancer therapies. RNA epitranscriptomics, the study of RNA modifications, is the new frontier of this arena. Despite being known since the 1970s, eukaryotic RNA modifications were mostly identified on transfer RNA and ribosomal RNA until the last decade, when they have been identified and characterized on mRNA and various non-coding RNAs. Increasing evidence suggests that RNA modification pathways are also misregulated in human cancers and may be ideal targets of cancer therapy. In this Review we highlight the RNA epitranscriptomic pathways implicated in cancer, describing their biological functions and their connections to the disease.

Separated Siamese Twins: Intronic Small Nucleolar RNAs and Matched Host Genes May be Altered in Conjunction or Separately in Multiple Cancer Types

Small nucleolar RNAs (snoRNAs) are non-coding RNAs involved in RNA modification and processing. Approximately half of the so far identified snoRNA genes map within the intronic regions of host genes, and their expression, as well as the expression of their host genes, is dependent on transcript splicing and maturation. Growing evidence indicates that mutations and/or deregulations that affect snoRNAs, as well as host genes, play a significant role in oncogenesis. Among the possible factors underlying snoRNA/host gene expression deregulation is copy number alteration (CNA). We analyzed the data available in The Cancer Genome Atlas database, relative to CNA and expression of 295 snoRNA/host gene couples in 10 cancer types, to understand whether the genetic or expression alteration of snoRNAs and their matched host genes would have overlapping trends. Our results show that, counterintuitively, copy number and expression alterations of snoRNAs and matched host genes are not necessarily coupled. In addition, some snoRNA/host genes are mutated and overexpressed recurrently in multiple cancer types. Our findings suggest that the differential contribution to cancer development of both snoRNAs and host genes should always be considered, and that snoRNAs and their host genes may contribute to cancer development in conjunction or independently.

The nucleolus: a central response hub for the stressors that drive cancer progression

The nucleolus is a sub-nuclear body known primarily for its role in ribosome biogenesis. Increased number and/or size of nucleoli have historically been used by pathologists as a prognostic indicator of cancerous lesions. This increase in nucleolar number and/or size is classically attributed to the increased need for protein synthesis in cancer cells. However, evidences suggest that the nucleolus plays critical roles in many cellular functions in both normal cell biology and disease pathologies, including cancer. As new functions of the nucleolus are elucidated, there is mounting evidence to support the role of the nucleolus in regulating additional cellular functions, particularly response to cellular stressors, maintenance of genome stability, and DNA damage repair, as well as the regulation of gene expression and biogenesis of several ribonucleoproteins. This review highlights the central role of the nucleolus in carcinogenesis and cancer progression and discusses how cancer cells may become "addicted" to nucleolar functions.

Stilbene Compounds Inhibit Tumor Growth by the Induction of Cellular Senescence and the Inhibition of Telomerase Activity

Cellular senescence is a state of cell cycle arrest characterized by a distinct morphology, gene expression pattern, and secretory phenotype. It can be triggered by multiple mechanisms, including those involved in telomere shortening, the accumulation of DNA damage, epigenetic pathways, and the senescence-associated secretory phenotype (SASP), and so on. In current cancer therapy, cellular senescence has emerged as a potent tumor suppression mechanism that restrains proliferation in cells at risk for malignant transformation. Therefore, compounds that stimulate the growth inhibition effects of senescence while limiting its detrimental effects are believed to have great clinical potential. In this review article, we first review the current knowledge of the pro- and antitumorigeneic functions of senescence and summarize the key roles of telomerase in the regulation of senescence in tumors. Second, we review the current literature regarding the anticancer effects of stilbene compounds that are mediated by the targeting of telomerase and cell senescence. Finally, we provide future perspectives on the clinical utilization of stilbene compounds, especially resveratrol and pterostilbene, as novel cancer therapeutic remedies. We conclude and propose that stilbene compounds may induce senescence and may potentially be used as the therapeutic or adjuvant agents for cancers with high telomerase activity.

Genomic amplification of HPV, h-TERC and c-MYC in liquid-based cytological specimens for screening of cervical intraepithelial neoplasia and cancer

Cervical cancer is one of the most prevalent female cancer types in developing countries. ThinPrep cytological test (TCT) and human papillomavirus (HPV) detection are canonical screening methods for cervical cancer currently. However, there are limitations to these techniques. The aim of the present study was to identify efficient and practical methods for the screening of cervical intraepithelial neoplasia (CIN) and carcinoma. Residual PreservCyt specimens were obtained from 1,000 women who were admitted between August 2013 and December 2015. TCT, human telomerase RNA component (h-TERC) fluorescent in situ hybridization (FISH), MYC-specific FISH and surface plasmon resonance (SPR)-HPV genotyping were performed, followed by histopathology for those patients with positive results in any of the four tests. As a result, 106, 64, 56 and 112 patients were positive in the TCT, h-TERC, c-MYC and SPR-HPV tests, respectively, resulting in 213 being scheduled for histopathology; inflammation was identified in 159 patients, CIN I in 31, CIN II in 14, CIN III in seven and invasive cervical cancer in two patients. Using histopathology as the gold standard, TCT exhibited the highest sensitivity (87.04%), while h-TERC analysis had the highest specificity (81.76%). Parallel tests demonstrated that the Youden's index of TCT + h-TERC was the highest (0.49), while the serial analysis reported that TCT + HPV had the highest Youden's index (0.53) compared with any of the biomarkers alone (TCT, 0.50; HPV, 0.29; h-TERC, 0.47). In conclusion, dual positive TCT and HPV may be an efficient approach for basic screening of cervical lesions. h-TERC amplification may serve as an auxiliary test to improve the specificity.

Overexpression of cellular telomerase RNA enhances virus-induced cancer formation

The telomerase RNA subunit (TR) is overexpressed in many tumors; however, the contribution of TR in cancer formation remains elusive. The most frequent clinically diagnosed cancer in the animal kingdom is caused by the highly oncogenic herpesvirus Marek's disease virus (MDV). MDV encodes a TR (vTR) that plays an important role in virus-induced tumorigenesis and shares 88% sequence identity with its cellular homologue. To determine if the cellular TR possesses pro-oncogenic activity, we replaced vTR with the cellular homologue in the virus genome. Insertion of cellular TR resulted in a strong overexpression in virus infected cells, while virus replication was not affected. Strikingly, cellular TR promoted tumor formation as efficient as vTR, while tumorigenesis was severely impaired in the absence of vTR. Our data provide the first evidence that overexpression of cellular TR can contribute to tumor formation in vivo using this natural virus-host model for herpesvirus-induced oncogenesis.

Turning Uridines around: Role of rRNA Pseudouridylation in Ribosome Biogenesis and Ribosomal Function

Ribosomal RNA (rRNA) is extensively edited through base methylation and acetylation, 2'-O-ribose methylation and uridine isomerization. In human rRNA, 95 uridines are predicted to by modified to pseudouridine by ribonucleoprotein complexes sharing four core proteins and differing for a RNA sequence guiding the complex to specific residues to be modified. Most pseudouridylation sites are placed within functionally important ribosomal domains and can influence ribosomal functional features. Information obtained so far only partially explained the degree of regulation and the consequences of pseudouridylation on ribosomal structure and function in different physiological and pathological conditions. This short review focuses on the available evidence in this topic, highlighting open questions in the field and perspectives that the development of emerging techniques is offering.

Telomere Maintenance Mechanisms in Cancer

Tumour cells can adopt telomere maintenance mechanisms (TMMs) to avoid telomere shortening, an inevitable process due to successive cell divisions. In most tumour cells, telomere length (TL) is maintained by reactivation of telomerase, while a small part acquires immortality through the telomerase-independent alternative lengthening of telomeres (ALT) mechanism. In the last years, a great amount of data was generated, and different TMMs were reported and explained in detail, benefiting from genome-scale studies of major importance. In this review, we address seven different TMMs in tumour cells: mutations of the TERT promoter (TERTp), amplification of the genes TERT and TERC, polymorphic variants of the TERT gene and of its promoter, rearrangements of the TERT gene, epigenetic changes, ALT, and non-defined TMM (NDTMM). We gathered information from over fifty thousand patients reported in 288 papers in the last years. This wide data collection enabled us to portray, by organ/system and histotypes, the prevalence of TERTp mutations, TERT and TERC amplifications, and ALT in human tumours. Based on this information, we discuss the putative future clinical impact of the aforementioned mechanisms on the malignant transformation process in different setups, and provide insights for screening, prognosis, and patient management stratification.

RNA Pseudouridylation in Physiology and Medicine: For Better and for Worse

Pseudouridine is the most abundant modification found in RNA. Today, thanks to next-generation sequencing techniques used in the detection of RNA modifications, pseudouridylation sites have been described in most eukaryotic RNA classes. In the present review, we will first consider the available information on the functional roles of pseudouridine(s) in different RNA species. We will then focus on how alterations in the pseudouridylation process may be connected with a series of human pathologies, including inherited disorders, cancer, diabetes, and viral infections. Finally, we will discuss how the availability of novel technical approaches are likely to increase the knowledge in this field.

Whole transcriptome analysis reveals dysregulated oncogenic lncRNAs in natural killer/T-cell lymphoma and establishes MIR155HG as a target of PRDM1

Natural killer/T-cell lymphoma is a rare but aggressive neoplasm with poor prognosis. Despite previous reports that showed potential tumor suppressors, such as PRDM1 or oncogenes associated with the etiology of this malignancy, the role of long non-coding RNAs in natural killer/T-cell lymphoma pathobiology has not been addressed to date. Here, we aim to identify cancer-associated dysregulated long non-coding RNAs and signaling pathways or biological processes associated with these long non-coding RNAs in natural killer/T-cell lymphoma cases and to identify the long non-coding RNAs transcriptionally regulated by PRDM1. RNA-Seq analysis revealed 166 and 66 long non-coding RNAs to be significantly overexpressed or underexpressed, respectively, in natural killer/T-cell lymphoma cases compared with resting or activated normal natural killer cells. Novel long non-coding RNAs as well as the cancer-associated ones such as SNHG5, ZFAS1, or MIR155HG were dysregulated. Interestingly, antisense transcripts of many growth-regulating genes appeared to be transcriptionally deregulated. Expression of ZFAS1, which is upregulated in natural killer/T-cell lymphoma cases, showed association with growth-regulating pathways such as stabilization of P53, regulation of apoptosis, cell cycle, or nuclear factor-kappa B signaling in normal and neoplastic natural killer cell samples. Consistent with the tumor suppressive role of PRDM1, we identified MIR155HG and TERC to be transcriptionally downregulated by PRDM1 in two PRDM1-null NK-cell lines when it is ectopically expressed. In conclusion, this is the first study that identified long non-coding RNAs whose expression is dysregulated in natural killer/T-cell lymphoma cases. These findings suggest that ZFAS1 and other dysregulated long non-coding RNAs may be involved in natural killer/T-cell lymphoma pathobiology through regulation of cancer-related genes, and loss-of-PRDM1 expression in natural killer/T-cell lymphomas may contribute to overexpression of MIR155HG; thereby promoting tumorigenesis.

The importance of being (slightly) modified: The role of rRNA editing on gene expression control and its connections with cancer

In human ribosomal RNAs, over 200 residues are modified by specific, RNA-driven enzymatic complexes or stand-alone, RNA-independent enzymes. In most cases, modification sites are placed in specific positions within important functional areas of the ribosome. Some evidence indicates that the altered control in ribosomal RNA modifications may affect ribosomal function during mRNA translation. Here we provide an overview of the connections linking ribosomal RNA modifications to ribosome function, and suggest how aberrant modifications may affect the control of the expression of key cancer genes, thus contributing to tumor development. In addition, the future perspectives in this field are discussed.