microRNA‑299‑3p inhibits laryngeal cancer cell growth by targeting human telomerase reverse transcriptase mRNA

Mining sponge phenomena in RNA expression data

In the last few years, the interactions among competing endogenous RNAs (ceRNAs) have been recognized as a key post-transcriptional regulatory mechanism in cell differentiation, tissue development, and disease. Notably, such sponge phenomena substracting active microRNAs from their silencing targets have been recognized as having a potential oncosuppressive, or oncogenic, role in several cancer types. Hence, the ability to predict sponges from the analysis of large expression data sets (e.g. from international cancer projects) has become an important data mining task in bioinformatics. We present a technique designed to mine sponge phenomena whose presence or absence may discriminate between healthy and unhealthy populations of samples in tumoral or normal expression data sets, thus providing lists of candidates potentially relevant in the pathology. With this aim, we search for pairs of elements acting as ceRNA for a given miRNA, namely, we aim at discovering miRNA-RNA pairs involved in phenomena which are clearly present in one population and almost absent in the other one. The results on tumoral expression data, concerning five different cancer types, confirmed the effectiveness of the approach in mining interesting knowledge. Indeed, 32 out of 33 miRNAs and 22 out of 25 protein-coding genes identified as top scoring in our analysis are corroborated by having been similarly associated with cancer processes in independent studies. In fact, the subset of miRNAs selected by the sponge analysis results in a significant enrichment of annotation for the KEGG32 pathway "microRNAs in cancer" when tested with the commonly used bioinformatic resource DAVID. Moreover, often the cancer datasets where our sponge analysis identified a miRNA as top scoring match the one reported already in the pertaining literature.

Modulation of telomerase expression and function by miRNAs: Anti-cancer potential

Telomerase is a nucleoprotein reverse transcriptase that maintains the telomere, a protective structure at the ends of the chromosome, and is active in cancer cells, stem cells, and fetal cells. Telomerase immortalizes cancer cells and induces unlimited cell division by preventing telomere shortening. Immortalized cancer cells have unlimited proliferative potential due to telomerase activity that causes tumorigenesis and malignancy. Therefore, telomerase can be a lucrative anti-cancer target. The regulation of catalytic subunit of telomerase (TERT) determines the extent of telomerase activity. miRNAs, as an endogenous regulator of gene expression, can control telomerase activity by targeting TERT mRNA. miRNAs that have a decreasing effect on TERT translation mediate modulation of telomerase activity in cancer cells by binding to TERT mRNA and regulating TERT translation. In this review, we provide an update on miRNAs that influence telomerase activity by regulation of TERT translation.

PITX1 protein interacts with ZCCHC10 to regulate hTERT mRNA transcription

Telomerase is a ribonucleoprotein ribonucleic enzyme that is essential for cellular immortalization via elongation of telomere repeat sequences at the end of chromosomes. Human telomerase reverse transcriptase (hTERT), the catalytic subunit of telomerase holoenzyme, is a key regulator of telomerase activity. Telomerase activity, which has been detected in the majority of cancer cells, is accompanied by hTERT expression, suggesting that this enzyme activity contributes to an unlimited replication potential of cancer cells via regulation of telomere length. Thus, hTERT is an attractive target for cancer-specific treatments. We previously reported that pared-like homeodomain 1 (PITX1) is a negative regulator of hTERT through direct binding to the hTERT promoter. However, the mechanism by which the function of PITX1 contributes to transcriptional silencing of the hTERT gene remains to be clarified. Here, we show that PITX1 and zinc finger CCHC-type containing 10 (ZCCHC10) proteins cooperate to facilitate the transcriptional regulation of the hTERT gene by functional studies via FLAG pull-down assay. Co-expression of PITX1 and ZCCHC10 resulted in inhibition of hTERT transcription, in melanoma cell lines, whereas mutate-deletion of homeodomain in PITX1 that interact with ZCCHC10 did not induce similar phenotypes. In addition, ZCCHC10 expression levels showed marked decrease in the majority of melanoma cell lines and tissues. Taken together, these results suggest that ZCCHC10-PITX1 complex is the functional unit that suppresses hTERT transcription, and may play a crucial role as a novel tumor suppressor complex.

Tumor‑suppressive miR‑299‑3p inhibits gastric cancer cell invasion by targeting heparanase

Gastric cancer (GC) remains a leading cause of cancer‑associated mortality globally. Emerging evidence suggests that microRNAs (miRs) function as oncogenes or tumor suppressors, contributing to various aspects of cancer progression, including invasion and metastasis. In the present study, the specific role of miR‑299‑3p in the invasion of GC cells was investigated. The expression level of miR‑299‑3p was measured using reverse transcription‑quantitative PCR and in situ hybridization in human GC tissues. Effects of miR‑299‑3p on GC cell invasion were determined by Transwell assay. Bioinformatics and luciferase reporter assays were performed to identify and verify the downstream effectors of miR‑299‑3p. miR‑299‑3p expression analysis in clinical GC samples revealed a significant downregulation of miR‑299‑3p compared with non‑tumor tissues. Inhibition of miR‑299‑3p promoted the invasive abilities of GC cells, whereas its overexpression significantly suppressed cell invasion. Bioinformatics and luciferase reporter assays identified heparanase (HPSE) as a direct target of miR‑299‑3p, the ectopic expression of which reversed the impairment in cell invasion induced by miR‑299‑3p upregulation. Furthermore, HPSE expression was negatively associated with miR‑299‑3p levels in human GC tissues. Overall, the present study indicated that miR‑299‑3p functions as a tumor suppressor by directly targeting HPSE, highlighting its potential as a target for the treatment of GC.

Diverse regulatory manners of human telomerase reverse transcriptase

Human telomerase reverse transcriptase (hTERT) is the core subunit of human telomerase and plays important roles in human cancers. Aberrant expression of hTERT is closely associated with tumorigenesis, cancer cell stemness maintaining, cell proliferation, apoptosis inhibition, senescence evasion and metastasis. The molecular basis of hTERT regulation is highly complicated and consists of various layers. A deep and full-scale comprehension of the regulatory mechanisms of hTERT is pivotal in understanding the pathogenesis and searching for therapeutic approaches. In this review, we summarize the recent advances regarding the diverse regulatory mechanisms of hTERT, including the transcriptional (promoter mutation, promoter region methylation and histone acetylation), post-transcriptional (mRNA alternative splicing and non-coding RNAs) and post-translational levels (phosphorylation and ubiquitination), which may provide novel perspectives for further translational diagnosis or therapeutic strategies targeting hTERT.

Signature microRNAs and long noncoding RNAs in laryngeal cancer recurrence identified using a competing endogenous RNA network

The aim of the present study was to identify novel microRNA (miRNA) or long noncoding RNA (lncRNA) signatures of laryngeal cancer recurrence and to investigate the regulatory mechanisms associated with this malignancy. Datasets of recurrent and nonrecurrent laryngeal cancer samples were downloaded from The Cancer Genome Atlas (TCGA) and the Gene Expression Omnibus database (GSE27020 and GSE25727) to examine differentially expressed miRNAs (DE-miRs), lncRNAs (DE-lncRs) and mRNAs (DEGs). miRNA-mRNA and lncRNA-miRNA networks were constructed by investigating the associations among these RNAs in various databases. Subsequently, the interactions identified were combined into a competing endogenous RNA (ceRNA) regulatory network. Feature genes in the miRNA-mRNA network were identified via topological analysis and a recursive feature elimination algorithm. A support vector machine (SVM) classifier was established using the betweenness centrality values in the miRNA-mRNA network, consisting of 32 optimal feature-coding genes. The classification effect was tested using two validation datasets. Furthermore, coding genes in the ceRNA network were examined via pathway enrichment analyses. In total, 21 DE-lncRs, 507 DEGs and 55 DE-miRs were selected. The SVM classifier exhibited an accuracy of 94.05% (79/84) for sample classification prediction in the TCGA dataset, and 92.66 and 91.07% in the two validation datasets. The ceRNA regulatory network comprised 203 nodes, corresponding to mRNAs, miRNAs and lncRNAs, and 346 lines, corresponding to the interactions among RNAs. In particular, the interactions with the highest scores were HLA complex group 4 (HCG4)-miR-33b, HOX transcript antisense RNA (HOTAIR)-miR-1-MAGE family member A2 (MAGEA2), EMX2 opposite strand/antisense RNA (EMX2OS)-miR-124-calcitonin related polypeptide α (CALCA) and EMX2OS-miR-124-γ-aminobutyric acid type A receptor γ2 subunit (GABRG2). Gene enrichment analysis of the genes in the ceRNA network identified that 11 pathway terms and 16 molecular function terms were significantly enriched. The SVM classifier based on 32 feature coding genes exhibited high accuracy in the classification of laryngeal cancer samples. miR-1, miR-33b, miR-124, HOTAIR, HCG4 and EMX2OS may be novel biomarkers of recurrent laryngeal cancer, and HCG4-miR-33b, HOTAIR-miR-1-MAGEA2 and EMX2OS-miR-124-CALCA/GABRG2 may be associated with the molecular mechanisms regulating recurrent laryngeal cancer.

Contributory role of microRNAs in anti-cancer effects of small molecule inhibitor of telomerase (BIBR1532) on acute promyelocytic leukemia cell line

Telomerase-mediated immortalization and proliferation of tumor cells is a promising anti-cancer treatment strategy and development of potent telomerase inhibitors is believed to open new window of treatments in human malignancies. In the present study, we found that BIBR1532, a small molecule inhibitor of human telomerase, exerted cytotoxic effects on a panel of human cancer cells spanning from solid tumors to hematologic malignancies; however, as compared with solid tumors, leukemic cells were more sensitive to this inhibitor. This was independent of molecular status of p53 in the leukemic cells. The results of a miRNA PCR array revealed that BIBR1532-induced cytotoxic effects in NB4, the most sensitive cell line, was coupled with alteration in a substantial number of cancer-related miRNAs. Interestingly, most of these miRNAs were found to act as tumor suppressors with validated targets in cell cycle or nuclear factor (NF)-κB-mediated apoptosis. In accordance with a bioinformatics analysis, our experimental studies showed that BIBR1532-induced apoptosis is mediated, at least partly, by inhibition of NF-κB. Moreover, we found that the alteration in the expression of miRNAs was coupled with the alteration in the cell cycle progression. To sum up with, a straightforward interpretation of our results is that telomerase inhibition using BIBR1532 not only induced CDKN1A-mediated G1 arrest in NB4, but also resulted in a caspase-3-dependent apoptotic cell death mostly through suppression of NF-κB axis.

Calpeptin attenuates cigarette smoke-induced pulmonary inflammation via suppressing calpain/IκBα signaling in mice and BEAS-2B cells

Exposure to cigarette smoke including secondhand smoking is the most important risk factor in the development of chronic obstructive pulmonary disease where incidence has substantially increased in recent decades. The mechanisms responsible for cigarette smoke-induced pulmonary inflammation remain unclear, and thus lack of effective treatment. The present study investigated the effect of calpeptin on attenuating cigarette smoke induced pulmonary inflammation and its potential mechanism and function. When BALB/c mice were exposed to cigarette smoke and received calpeptin intraperitoneally injection after 90 days, calpeptin histologically attenuated the accumulation of neutrophils (P < 0.001), eosinophils (P < 0.001), macrophages (P < 0.01), fibrinous exudation and proliferation within the interstitial and alveolar spaces. BEAS-2B cells were added with cigarette smoke extract in vitro and treated with calpeptin for 24 h in the treatment group. The markedly upregulation of μ-calpain (P < 0.01), m-calpain (P < 0.001) and IκBα (P < 0.01) in cigarette smoke-induced lungs were simultaneously decreased by calpeptin treatment (P < 0.05). The increased expression of μ-calpain, m-calpain and IκBα (P < 0.05) in cigarette smoke extract-stimulated BEAS-2B cells were also decreased by calpeptin treatment (P < 0.05). These data indicated that calpeptin attenuated cigarette smoke-induced pulmonary inflammation by suppressing the pathway of μ-calpain, m-calpain and IκBα in vivo and in vitro. Calpeptin might have a potential for prevention of the development of inflammatory pulmonary diseases and warrant further pharmaceutical investigation.

MicroRNA-299-3p regulates proliferation, migration and invasion of human ovarian cancer cells by modulating the expression of OCT4

Ovarian cancer is among the most prevalent and lethal types of cancers in women. Several factors such as late diagnosis, unavailability of the reliable biomarkers, frequent relapses and dearth of efficient therapeutic targets form bottleneck in the treatment of ovarian cancers. In this study we investigated the potential of less studied miR-299-3p as the therapeutic target for the treatment of ovarian cancer. The results of the present investigation revealed that miR-299 is significantly upregulated in the ovarian cancers and suppression of its expression inhibits the proliferation by induction of apoptosis as well suppresses migration and invasion of the SKOV3 cancers cells. Further, OCT-4 was found to be putative target of miR-99-3p in ovarian cancer and inhibition of OCT-4 had similar effects as that of miR-299 inhibition on cell migration and invasion. Intriguingly, even overexpression of miR-299-3p could not rescue the effects of OCT-4 suppression on SKOV3 cell proliferation, migration and invasion. On contrary, overexpression of OCT-4 in SKOV3 cells transfected with miR-299-3p transfected could nullify the effects of miR-200-3p on proliferation, migration and invasion of the SKOV3 cells. Taken together, miR-299-3p regulated cell proliferation and metastasis by modulating the expression of OCT-4 and as such may prove to be an important therapeutic target.

MicroRNA Regulation of Telomerase Reverse Transcriptase (TERT): Micro Machines Pull Strings of Papier-Mâché Puppets

Substantial fraction of high-quality information is continuously being added into the existing pool of knowledge related to the biology of telomeres. Based on the insights gleaned from decades of research, it is clear that chromosomal stability needs a highly controlled and dynamic balance of DNA gain and loss in each terminal tract of telomeric repeats. Telomeres are formed by tandem repeats of TTAGGG sequences, which are gradually lost with each round of division of the cells. Targeted inhibition of telomerase to effectively induce apoptosis in cancer cells has attracted tremendous attention and overwhelmingly increasingly list of telomerase inhibitors truthfully advocates pharmacological significance of telomerase. Telomerase reverse transcriptase (TERT) is a multi-talented and catalytically active component of the telomerase-associated protein machinery. Different proteins of telomerase-associated machinery work in a synchronized and orchestrated manner to ensure proper maintenance of telomeric length of chromosomes. Rapidly emerging scientific findings about regulation of TERT by microRNAs has revolutionized our understanding related to the biology of telomeres and telomerase. In this review, we have comprehensively discussed how different miRNAs regulate TERT in different cancers. Use of miRNA-based therapeutics against TERT in different cancers needs detailed research in preclinical models for effective translation of laboratory findings to clinically effective therapeutics.

miR-632 Promotes Laryngeal Carcinoma Cell Proliferation, Migration, and Invasion Through Negative Regulation of GSK3β

Laryngeal cancer, one of the most common head and neck malignancies, is an aggressive neoplasm. Increasing evidence has demonstrated that microRNAs (miRNAs) exert important roles in oncogenesis and progression of diverse types of human cancers. miR-632, a tumor-related miRNA, has been reported to be dysregulated and implicated in human malignancies; however, its biological role in laryngeal carcinoma remains to be elucidated. The present study aimed at exploring the role of miR-632 in laryngeal cancer and clarifying the potential molecular mechanisms involved. In the current study, miR-632 was found to be significantly upregulated both in laryngeal cancer tissues and laryngeal cancer cell lines. Functional studies demonstrated that miR-632 accelerated cell proliferation and colony formation, facilitated cell migration and invasion, and enhanced the expression of cell proliferation-associated proteins, cyclin D1 and c-myc. Notably, miR-632 could directly bind to the 3′-untranslated region (3′-UTR) of glycogen synthase kinase 3β (GSK3β) to suppress its expression in laryngeal cancer cells. Mechanical studies revealed that miR-632 promoted laryngeal cancer cell proliferation, migration, and invasion through negative modulation of GSK3β. Pearson’s correlation analysis revealed that miR-632 expression was inversely correlated with GSK3β mRNA expression in laryngeal cancer tissues. Taken together, our findings suggest that miR-632 functions as an oncogene in laryngeal cancer and may be used as a novel therapeutic target for laryngeal cancer.

MiRNA-mRNA crosstalk in laryngeal squamous cell carcinoma based on the TCGA database

BACKGROUND

The functional characterization of non-coding microRNAs (miRNAs) has been shown to be associated with the pathophysiology of the disease, but it is still a challenging task to elucidate the pathogenesis of microRNAs and disease. In addition, the understanding of the role of miRNAs in the development of LSCC still needs further exploration.

MATERIALS AND METHODS

In this study, to identify miRNAs that play a key role in LSCC, we analyzed miRNA and mRNA sequence data from 162 LSCC samples from the TCGA database, and screened specific miRNAs and mRNAs by differential gene expression analysis. And then, construct a differentially expressed miRNAs and mRNAs interaction network.

RESULTS

In our investigation, 23 miRNAs (P < 0.01, log2FoldChange > 2) and 331 mRNAs (P < 0.01, log2FoldChange > 4) were identified differentially expressed in LSCC and reduced the number of loosely linked miRNAs and mRNAs according to appropriate thresholds. Finally, 13 miRNAs and 35 mRNAs were enriched in a network.

CONCLUSIONS

Our study provides the most comprehensive information on the expression of miRNAs in LSCC and identifies the known oncogenic miRNAs (such as miR-163a), as well as aberrant expression of novel miRNAs involved in cell regulation and metabolic defects that occur during development of LSCC.

MicroRNA-299-3p suppresses proliferation and invasion by targeting VEGFA in human colon carcinoma

Accumulating evidences have shown that microRNAs (miRNAs) are vital regulators and possess huge capabilities in post-transcriptional control. Although a large number of miRNAs have been identified to be dysregulated in human cancers especially in colon cancer, our understandings of the function of most miRNAs are still largely limited. In this study, we have demonstrated that miR-299-3p plays a critical role in suppressing colon carcinoma progression by targeting Vascular Endothelial Growth Factor A (VEGFA). We observed that miR-299-3p was down-regulated in colon carcinoma tissues and colon cancer cell lines. The level of miR-299-3p was significantly negatively correlated with that of VEGFA mRNA level in colon carcinoma. More importantly, the low level of miR-299-3p predicted poor prognosis of colon cancer patients. Functionally, overexpression of miR-299-3p inhibited the proliferation and invasion of colon carcinoma cells and suppressed the growth of colon cancer xenografts in nude mice. Luciferase reporter assays showed that miR-299-3p could target VEGFA 3' UTR. In addition, up-regulation of miR-299-3p decreased VEGFA expression both in vitro and in vivo, showing that miR-299-3p plays a suppressive effect on VEGFA via post-transcriptional control. However, ectopical expression of VEGFA could abrogate this effect and also abolish miR-299-3p-induced inhibition of cell proliferation and invasion. Taken together, our study provides evidences showing that miR-299-3p functions as a suppressor in colon cancer by targeting VEGFA, suggesting that miR-299-3p might serve as a novel target for colon cancer therapy.

Epigenetic perturbation driving asleep telomerase reverse transcriptase: Possible therapeutic avenues in carcinoma

In the last decade, implications of human telomerase reverse transcriptase (hTERT), a component of ribonucleoprotein telomerase in aging, senescence, and stem cell are highly evident. Besides, the activation of hTERT is also being documented several cancer types including carcinoma. The awakening of telomerase during carcinoma initiation and development is being seen with different perspectives including genetic and epigenetic tools and events. In view of several tumor progenitors genes (also referred as epigenetic mediators), telomerase is placed as key enzyme to achieve the carcinoma phenotype and sustain during the progression. It is true that swaying of telomerase in carcinoma could be facilitated with dedicated set of epigenetic modulators and modifiers players. These epigenetic alterations are heritable, potentially reversible, and seen as the epigenetic signature of carcinoma. Several papers converge to suggest that DNA methylation, histone modification, and small non-coding RNAs are the widely appreciated epigenetic changes towards hTERT modulation. In this review, we summarize the contribution of epigenetic factors in the telomerase activation and discuss potential avenues to achieve therapeutic intervention in carcinoma.

MicroRNA-532 and microRNA-3064 inhibit cell proliferation and invasion by acting as direct regulators of human telomerase reverse transcriptase in ovarian cancer

Human telomerase reverse transcriptase (hTERT) plays a crucial role in ovarian cancer (OC) progression. However, the mechanisms underlying hTERT upregulation in OC, and the specific microRNAs (miRNAs) involved in the regulation of hTERT in OC cells, remains unclear. We performed a bioinformatics search to identify potential miRNAs that bind to the 3'-untranslated region (3'-UTR) region of the hTERT mRNA. We examined the expression levels of miR-532/miR-3064 in OC tissues and normal ovarian tissues, and analyzed the correlation between miRNA expression and OC patient outcomes. The impacts of miR-532/miR-3064 on hTERT expression were evaluated by western blot analysis and hTERT 3'-UTR reporter assays. We investigated the effects of miR-532/miR-3064 on proliferation and invasion in OC cells. We found that miR-532 and miR-3064 are down-regulated in OC specimens. We observed a significant association between reduced miR-532/miR-3064 expression and poorer survival of patients with OC. We confirmed that in OC cells, these two miRNAs downregulate hTERT levels by directly targeting its 3'-UTR region, and inhibited proliferation, EMT and invasion of OC cells. In addition, the overexpression of the hTERT cDNA lacking the 3'-UTR partially restored miR-532/miR-3064-inhibited OC cell proliferation and invasion. The silencing of hTERT by siRNA oligonucleotides abolished these malignant features, and phenocopied the effects of miR-532/miR-3064 overexpression. Furthermore, overexpression of miR-532/miR-3064 inhibits the growth of OC cells in vivo. Our findings demonstrate a miR-532/miR-3064-mediated mechanism responsible for hTERT upregulation in OC cells, and reveal a possibility of targeting miR-532/miR-3064 for future treatment of OC.

The role of microRNAs expression in laryngeal cancer

MicroRNAs (miRs, miRs) is a class of small non-coding RNAs, which posttranscriptionally regulate gene expression. Deregulated miRs are frequently obseved in patients with laryngeal cancer. In addition, numerous studies have showed miRs play significant roles in the pathogenesis of laryngeal cancer through regulating tumor cell proliferation, metastasis, invasion and apoptosis. miR can play either an oncogenic or tumor suppressive role in laryngeal cancer. In our review, we summarize the recent researches on laryngeal cancer-associated miRs, focusing on their role in the pathogenesis of laryngeal cancer. As changes in the levels of specific miRs in tissues or serum associate with diagnosis and prognosis of patients, we will also discuss the potential use of miRs in laryngeal cancer diagnosis and prognosis. Furthermore, supplementation of oncomiRs or inhibition of tumor suppressive miRs in vivo may be future therapeutic strategy for laryngeal cancer.