Let-7c inhibits A549 cell proliferation through oncogenic TRIB2 related factors

MiRNAs in Lung Adenocarcinoma: Role, Diagnosis, Prognosis, and Therapy

Lung cancer has emerged as a significant public health challenge and remains the leading cause of cancer-related mortality worldwide. Among various types of lung malignancies, lung adenocarcinoma (LUAD) stands as the most prevalent form. MicroRNAs (miRNAs) play a crucial role in gene regulation, and their involvement in cancer has been extensively explored. While several reviews have been published on miRNAs and lung cancer, there remains a gap in the review regarding miRNAs specifically in LUAD. In this review, we not only highlight the potential diagnostic, prognostic, and therapeutic implications of miRNAs in LUAD, but also present an inclusive overview of the extensive research conducted on miRNAs in this particular context.

Oncogenic TRIB2 interacts with and regulates PKM2 to promote aerobic glycolysis and lung cancer cell procession

PKM2 is an important regulator of the aerobic glycolysis that plays a vital role in cancer cell metabolic reprogramming. In general, Trib2 is considered as a “pseudokinase”, contributing to different kinds of cancer. However, the detailed roles of TRIB2 in regulating cancer metabolism by PKM2 remain unclear. This study demonstrated that TRIB2, not a “pseudokinase”, has the kinase activity to directly phosphorylate PKM2 at serine 37 in cancer cells. The elevated pSer37-PKM2 would subsequently promote the PKM2 dimers to enter into nucleus and increase the expression of LDHA, GLUT1, and PTBP1. The aerobic glycolysis is then elevated to promote cancer cell proliferation and migration in TRIB2- or PKM2-overexpressed cultures. The glucose uptake and lactate production increased, but the ATP content decreased in TRIB2- or PKM2-treated cultures. Experiments of TRIB2^−/− mice further supported that TRIB2 could regulate aerobic glycolysis by PKM2. Thus, these results reveal the new kinase activity of TRIB2 and its mechanism in cancer metabolism may be related to regulating PKM2 to promote lung cancer cell proliferation in vitro and in vivo, suggesting promising therapeutic targets for cancer therapy by controlling cancer metabolism.

RFWD2 Knockdown as a Blocker to Reverse the Oncogenic Role of TRIB2 in Lung Adenocarcinoma

RFWD2, an E3 ubiquitin ligase, is overexpressed in numerous human cancers, including leukemia, lung cancer, breast cancer, renal cell carcinoma, and colorectal cancer. The roles of RFWD2 in cancer are related to the targeting of its substrates for ubiquitination and degradation. This study aimed to investigate the role of TRIB2 in relation to the regulation of protein degradation through RFWD2. inBio Discover™ results demonstrated that TRIB2 can perform its functions by interacting with RFWD2 or other factors. TRIB2 can interact with and regulate RFWD2, which further attends the proteasome-mediated degradation of the RFWD2 substrate p-IκB-α. TRIB2 colocalizes with RFWD2-related IκB-α to form a ternary complex and further affects the IκB-α degradation by regulating its phosphorylation. Specific domain analysis showed that TRIB2 may bind to RFWD2 via its C-terminus, whereas it binds to IκB via its pseudokinase domain. TRIB2 acts as an oncogene and promotes cancer cell proliferation and migration, whereas RFWD2 knockdown reversed the role of TRIB2 in promoting cancer cell growth and colony formation in vitro and in vivo. In summary, this study reveals that TRIB2 promotes the progression of cancer by affecting the proteasome-mediated degradation of proteins through the interaction with RFWD2.

miR-4293 upregulates lncRNA WFDC21P by suppressing mRNA-decapping enzyme 2 to promote lung carcinoma proliferation

Non-coding RNAs (ncRNAs) involve in diverse biological processes by post-transcriptional regulation of gene expression. Emerging evidence shows that miRNA-4293 plays a significant role in the development of non-small cell lung cancer. However, the oncogenic functions of miR-4293 have not been studied. Our results demonstrated that miR-4293 expression is markedly enhanced in lung carcinoma tissue and cells. Moreover, miR-4293 promotes tumor cell proliferation and metastasis but suppresses apoptosis. Mechanistic investigations identified mRNA-decapping enzyme 2 (DCP2) as a target of miR-4293 and its expression is suppressed by miR-4293. DCP2 can directly or indirectly bind to WFDC21P and downregulates its expression. Consequently, miR-4293 can further promote WFDC21P expression by regulating DCP2. With a positive correlation to miR-4293 expression, WFDC21P also plays an oncogenic role in lung carcinoma. Furthermore, knockdown of WFDC21P results in functional attenuation of miR-4293 on tumor promotion. In vivo xenograft growth is also promoted by both miR-4293 and WFDC21P. Overall, our results establish oncogenic roles for both miR-4293 and WFDC21P and demonstrate that interactions between miRNAs and lncRNAs through DCP2 are important in the regulation of carcinoma pathogenesis. These results provided a valuable theoretical basis for the discovery of lung carcinoma therapeutic targets and diagnostic markers based on miR-4293 and WFDC21P.

Lin28A promotes the proliferation and stemness of lung cancer cells via the activation of mitogen-activated protein kinase pathway dependent on microRNA let-7c

Background

Among patients with lung cancer, metastatic and relapsed cases account for the largest proportion of disease-associated deaths. Tumor metastasis and relapse are believed to originate from cancer stem cells (CSCs), which have the capacity to be highly proliferative and invasive. In our previous studies, we established a conditional basement membrane extract-based (BME-based) 3-dimensional (3D) culture system to mimic the tumor growth environment in vivo and further amplified lung cancer stem cells (LCSCs) in our system. However, the molecular mechanisms of LCSC amplification and development in our 3D culture system have not been fully uncovered.

Method

We established the conditional 3D culture system to amplify LCSCs in other lung cancer cell lines, followed by examining the expression of Lin28A and let-7 microRNAs in them. We also explored the expression of Lin28A and let-7 microRNAs in LCSCs from clinical lung cancer tissue samples and even analyzed the correlation of Lin28A/let-7c and patients’ survival outcomes. We further constructed A549 cells either knockdown of Lin28A or overexpression of let-7c, followed by investigating stemness marker gene expression, and stemness phenotypes including mammosphere culture, cell migration and invasion in vitro, as well as tumorigenicity in vivo.

Results

Here, we observed that Lin28A/let-7c was dysregulated in LCSCs in both the 3D culture system and lung cancer tissues. Further, the abnormal expression of Lin28A/let-7c was correlated with poor survival outcomes. Via the construction of A549 cells with let-7c over-expression, we found that let-7c inhibited the maintenance of LCSC properties, while the results of Lin28A knockdown showed that Lin28A played a critical role in the enrichment and proliferation of LCSCs via mitogen-activated protein kinase (MAPK) signaling pathway. Importantly, we found that LCSCs with knockdown of Lin28A or over-expression of let-7c exhibited inhibited carcinogenesis and disrupted expansion in vivo.

Conclusions

Our study uncovered the functions and mechanisms of the Lin28A/let-7c/MAPK signaling pathway in promoting the proliferation and cancer stemness of LCSCs, which might be a potential therapeutic target for reducing and even eliminating LCSCs in the future.

The Critical Role of TRIB2 in Cancer and Therapy Resistance

Simple Summary

The Tribbles proteins are members of CAMK Ser/Thr protein kinase family. They are evolutionary conserved pseudokinases found in most tissues of eukaryotic organisms. This ubiquitously expressed protein family is characterized by containing a catalytically deficient kinase domain which lacks amino acid residues required for the productive interaction with ATP and metal ions. Tribbles proteins exert their biological functions mainly through direct interaction with MAPKK and AKT proteins, therefore regulating important pathways involved in cell proliferation, apoptosis and differentiation. Due to the role of MAPKK and AKT signalling in the context of cancer development, Tribbles proteins have been recently considered as biomarkers of cancer progression. Furthermore, as the atypical pseudokinase domain retains a binding platform for substrates, Tribbles targeting provides an attractive opportunity for drug development.

Abstract

The Tribbles pseudokinases family consists of TRIB1, TRIB2, TRIB3 and STK40 and, although evolutionarily conserved, they have distinctive characteristics. Tribbles members are expressed in a context and cell compartment-dependent manner. For example, TRIB1 and TRIB2 have potent oncogenic activities in vertebrate cells. Since the identification of Tribbles proteins as modulators of multiple signalling pathways, recent studies have linked their expression with several pathologies, including cancer. Tribbles proteins act as protein adaptors involved in the ubiquitin-proteasome degradation system, as they bridge the gap between substrates and E3 ligases. Between TRIB family members, TRIB2 is the most ancestral member of the family. TRIB2 is involved in protein homeostasis regulation of C/EBPα, β-catenin and TCF4. On the other hand, TRIB2 interacts with MAPKK, AKT and NFkB proteins, involved in cell survival, proliferation and immune response. Here, we review the characteristic features of TRIB2 structure and signalling and its role in many cancer subtypes with an emphasis on TRIB2 function in therapy resistance in melanoma, leukemia and glioblastoma. The strong evidence between TRIB2 expression and chemoresistance provides an attractive opportunity for targeting TRIB2.

Hsa-let-7c exerts an anti-tumor function by negatively regulating ANP32E in lung adenocarcinoma

We attempted to investigate the relationship between hsa-let-7c and ANP32E, as well as their influence on the cells phenotype of lung adenocarcinoma. Expression of hsa-let-7c and prognostic values were assessed by bioinformatics analysis based on TCGA database. Quantitative real-time PCR and western blot was employed to measure relative expression of hsa-let-7c or ANP32E. The targeting relationship between let-7c and ANP32E was predicted by biological software and validated by dual luciferase reporter assay. With gene transfection technology, cell proliferation, invasion and migration were appraised by cell counting Kit-8, clone formation and Transwell assays. The results showed that hsa-let-7c was downregulated in lung adenocarcinoma. Downregulation of hsa-let-7c notably led to a poor survival. ANP32E was forecasted and confirmed as a directly target of hsa-let-7c, and was upregulated in lung adenocarcinoma. Furthermore, upregulation of ANP32E had a significant correlation with unsatisfactory survival. Meanwhile, the levels of ANP32E were negatively regulated by hsa-let-7c. Upregulation of hsa-let-7c remarkably suppressed the Calu-3 cell proliferation, invasion and migration, while ANP32E overexpression plasmids rescued the downtrend. Inversely, hsa-let-7c silencing in NCI-H209 cells presented the opposite outcomes. Collectively, hsa-let-7c shows an anti-tumor effect in lung adenocarcinoma by targeting ANP32E and is expected to be a potential therapeutic target for lung adenocarcinoma.

Cisplatin decreases cyclin D2 expression via upregulating miR‑93 to inhibit lung adenocarcinoma cell growth

MicroRNAs (miRNAs/miRs) serve important roles in the chemotherapeutic effect of anticancer drugs. To investigate the roles of miRNAs in cisplatin‑induced suppression of lung adenocarcinoma cell proliferation, A549 cells were treated with different concentrations of cisplatin. An MTT assay demonstrated that cisplatin inhibited A549 cell proliferation in a dose‑dependent manner. Cisplatin induced cell apoptosis and inhibited cell migration by increasing the levels of miR‑93, miR‑26a and miR‑26b. Furthermore, as an upstream factor, miR‑93 was proposed to regulate cyclin D2 expression in miR‑93‑transfected A549 cells. Cisplatin also induced Bcl‑2‑associated X protein expression, and decreased that of Bcl‑2 and c‑Myc in lung adenocarcinoma cells. In vivo analysis further supported that cisplatin inhibited lung adenocarcinoma cell growth by regulating cyclin D2 and miR‑93 expression. In conclusion, our findings demonstrated that cisplatin could effectively inhibit lung adenocarcinoma cell proliferation by decreasing cyclin D2 expression via miR‑93.

MicroRNA-let-7c suppresses hepatitis C virus replication by targeting Bach1 for induction of haem oxygenase-1 expression

MicroRNAs are small noncoding RNAs that are central factors between hepatitis C virus (HCV) and host cellular factors for viral replication and liver disease progression, including liver fibrosis, cirrhosis and hepatocellular carcinoma. In the present study, we found that overexpressing miR-let-7c markedly reduced HCV replication because it induced haem oxygenase-1 (HO-1) expression by targeting HO-1 transcriptional repressor Bach1, ultimately leading to stimulating an antiviral interferon response and blockade of HCV viral protease activity. In contrast, the antiviral actions of miR-let-7c were attenuated by miR-let-7c inhibitor treatment, exogenously expressing Bach1 or suppressing HO-1 activity and expression. A proposed model indicates a key role for miR-let-7c targeting Bach1 to transactivate HO-1-mediated antiviral actions against HCV. miR-let-7c may serve as an attractive target for antiviral development.

Induction of microRNA‑let‑7a inhibits lung adenocarcinoma cell growth by regulating cyclin D1

Lung cancer is the most common cause of cancer‑associated mortality. MicroRNAs (miRNAs), as oncogenes or tumor suppressor genes, serve crucial roles not only in tumorigenesis, but also in tumor invasion and metastasis. Although miRNA‑let‑7a (let‑7a) has been reported to suppress cell growth in multiple cancer types, the biological mechanisms of let‑7a in lung adenocarcinoma are yet to be fully elucidated. In the present study, the molecular roles of let‑7a in lung adenocarcinoma were investigated by detecting its expression in lung adenocarcinoma tissues and exploring its roles in the regulation of lung cancer cell proliferation. Let‑7a expression was identified to be downregulated in lung adenocarcinoma tissues compared with normal tissues. Overexpression of let‑7a effectively suppressed cancer cell proliferation, migration and invasion in H1299 and A549 cells. Let‑7a also induced cell apoptosis and cell cycle arrest. Furthermore, let‑7a significantly inhibited cell growth by directly regulating cyclin D1 signals. This novel regulatory mechanism of let‑7a in lung adenocarcinoma provides possible avenues for future targeted therapies of lung cancer.

Effects of let-7c on the proliferation of ovarian carcinoma cells by targeted regulation of CDC25a gene expression

MicroRNAs serve a role in the development of ovarian cancer (OC). The present study investigated whether let-7c is able to regulate the proliferation of OC cells by targeting cell division cycle 25A (CDC25a). The reverse transcription-quantitative polymerase chain reaction was performed to detect the expression of let-7c in OC specimens. Let-7c agomir was transfected into OC cells, and the proliferation and apoptosis of OC cells were detected. A dual-luciferase assay and western blotting were performed to analyze whether CDC25a was the target gene of let-7c as well as its interaction site. The results revealed that, in OC tissue, let-7c was downregulated when compared with normal ovarian tissue. A Cell Counting Kit-8 (CCK8) assay, colony formation assay and flow cytometry demonstrated that increased expression of let-7c was able to inhibit the proliferation and increase the apoptosis of OC cells. Western blotting revealed that upregulated let-7c is able to decrease the expression of CDC25a, and a dual-luciferase assay and a recovery assay demonstrated that let-7c was able to regulate the expression of the 3' untranslated region of CDC25a. Therefore, the roles of let-7c in inhibiting the proliferation and promoting the apoptosis of OC cells may be realized through the regulation of the expression of CDC25a. The results of the present study revealed that let-7c may be a novel target in the diagnosis and treatment of OC.

Profile of epigenetic mechanisms in lung tumors of patients with underlying chronic respiratory conditions

Background

Chronic lung diseases such as chronic obstructive pulmonary disease (COPD) and epigenetic events underlie lung cancer (LC) development. The study objective was that lung tumor expression levels of specific microRNAs and their downstream biomarkers may be differentially regulated in patients with and without COPD.

Methods

In lung specimens (tumor and non-tumor), microRNAs known to be involved in lung tumorigenesis (miR-21, miR-200b, miR-126, miR-451, miR-210, miR-let7c, miR-30a-30p, miR-155 and miR-let7a, qRT-PCR), DNA methylation, and downstream biomarkers were determined (qRT-PCR and immunoblotting) in 40 patients with LC (prospective study, subdivided into LC-COPD and LC, N = 20/group).

Results

Expression of miR-21, miR-200b, miR-210, and miR-let7c and DNA methylation were greater in lung tumor specimens of LC-COPD than of LC patients. Expression of downstream markers PTEN, MARCKs, TPM-1, PDCD4, SPRY-2, ETS-1, ZEB-2, FGFRL-1, EFNA-3, and k-RAS together with P53 were selectively downregulated in tumor samples of LC-COPD patients. In these patients, tumor expression of miR-126 and miR-451 and that of the biomarkers PTEN, MARCKs, FGFRL-1, SNAIL-1, P63, and k-RAS were reduced.

Conclusions

Biomarkers of mechanisms involved in tumor growth, angiogenesis, migration, and apoptosis were differentially expressed in tumors of patients with underlying respiratory disease. These findings shed light into the underlying biology of the reported greater risk to develop LC seen in patients with chronic respiratory conditions. The presence of an underlying respiratory disease should be identified in all patients with LC as the differential biological profile may help determine tumor progression and the therapeutic response. Additionally, epigenetic events offer a niche for pharmacological therapeutic targets.

Celastrol suppresses the proliferation of lung adenocarcinoma cells by regulating microRNA-24 and microRNA-181b

Cumulative evidence has indicated that celastrol may suppress cancer growth; however, the underlying mechanism requires further investigation. In the present study, A549 cells were treated with various concentrations of celastrol. Lung cancer cell proliferation was evaluated using an MTT assay and observed under a microscope. Cell apoptosis was detected by Annexin V fluorescein isothiocyanate/propidium iodide double-labeled flow cytometry. The results demonstrated that celastrol suppressed proliferation and induced apoptosis in a dose-independent manner. Celastrol may also decrease the phosphorylation levels of signal transducer and activator of transcription 3 (STAT3) and the B cell lymphoma-2 (Bcl-2)/Bcl-2 associated C protein (Bax) ratio. As microRNA (miR-24 and miR-181b) were predicated to target STAT3, STAT3 activation was inhibited in miR-24-or miR-181b-treated A549 cells compared with the control treatment. The ratio of Bcl-2/Bax was further reduced in miR-24 or miR-181b-treated A549 cells. The results were further confirmed by detecting in another lung adenocarcinoma cell line, LTEP-a-2. In summary, the results of the present study demonstrated that celastrol treatment suppressed the proliferation and induced apoptosis by regulating the expression levels of miR-24 and miR-181b.

TRIB2 contributes to cisplatin resistance in small cell lung cancer

Small cell lung cancer (SCLC) is the most aggressive lung-cancer subtype and so far, no favorable therapeutic strategy has been established for chemo-resistant SCLC. Cisplatin is one of the most important components among all standard poly-chemotherapeutic regimens for SCLC; therefore, this study focused on revealing Cisplatin-resistance mechanism(s) in this disease. Cisplatin-resistant SCLC cells were generated in the NCI-H69 xenograft model in nude mice by continuous intravenous administration of Cisplatin; Cisplatin resistance of the tumor cells was confirmed by in vitro and in vivo tests, and the gene expression profile of the resistant cells was determined using microarray analysis. A significantly higher expression of tribbles pseudokinase 2 (TRIB2) mRNA in the Cisplatin-resistant cells was found compared to parental H69 cells. Further, the Cisplatin-resistance level was decreased when TRIB2 expression was knocked down. The mRNA and protein levels of CCAAT/enhancer binding protein alpha (CEBPA), known to be a transcription factor regulating cell differentiation and a target for degradation by TRIB2, as well as selected cancer stem cell makers in the Cisplatin-resistant cells, were measured. We found that CEBPA protein levels could be upregulated by knocking down the overexpressed TRIB2, which also reversed the Cisplatin-resistance of these cells; further, the Cisplatin-resistant SCLC cells demonstrated certain cancer stem cell-like properties. Similar patterns were also observed in limited human tumor specimens of chemo-resistant SCLC patients: namely, overexpressed TRIB2 and undetected CEBPA proteins. Our study revealed a possible molecular mechanism for Cisplatin-resistant SCLC involving induced TRIB2 overexpression and downregulation of CEBPA protein. We propose that this mechanism is a potential therapeutic target to circumvent chemo-resistance in SCLC.

Down syndrome and microRNAs

In recent years numerous studies have indicated the importance of microRNAs (miRNA/miRs) in human pathology. Down syndrome (DS) is the most prevalent survivable chromosomal disorder and is attributed to trisomy 21 and the subsequent alteration of the dosage of genes located on this chromosome. A number of miRNAs are overexpressed in down syndrome, including miR-155, miR-802, miR- 125b-2, let-7c and miR-99a. This overexpression may contribute to the neuropathology, congenital heart defects, leukemia and low rate of solid tumor development observed in patients with DS. MiRNAs located on other chromosomes and with associated target genes on or off chromosome 21 may also be involved in the DS phenotype. In the present review, an overview of miRNAs and the haploinsufficiency and protein translation of specific miRNA targets in DS are discussed. This aimed to aid understanding of the pathogenesis of DS, and may contribute to the development of novel strategies for the prevention and treatment of the pathologies of DS.

Taurine ameliorates particulate matter-induced emphysema by switching on mitochondrial NADH dehydrogenase genes

Exposure to high levels of particulate matter (PM) poses a major threat to human health. Cigarette smoke is the most common irritant that causes chronic obstructive pulmonary disease (COPD); however, at least one-fourth of patients with COPD are nonsmokers, and their disease is largely attributed to air pollution. The occurrence of pollution episodes in China has raised an emergent question of how PM leads to the pathogenesis of COPD. In this paper, we show that deregulation of mitochondrial NADH dehydrogenase gene expression levels plays a key role in the aggravation of COPD during air pollutant exposure, which can be rescued by taurine and 3-MA treatments in both mammalian cells and animals.

Chronic obstructive pulmonary disease (COPD) has been linked to particulate matter (PM) exposure. Using transcriptomic analysis, we demonstrate that diesel exhaust particles, one of the major sources of particulate emission, down-regulated genes located in mitochondrial complexes I and V and induced experimental COPD in a mouse model. 1-Nitropyrene was identified as a major toxic component of PM-induced COPD. In the panel study, COPD patients were found to be more susceptible to PM than individuals with normal lung function due to an increased inflammatory response. Mechanistically, exposure to PM in human bronchial epithelial cells led to a decline in CCAAT/enhancer-binding protein alpha (C/EBPα), which triggered aberrant expression of NADH dehydrogenase genes and ultimately led to enhanced autophagy. ATG7-deficient mice, which have lower autophagy rates, were protected from PM-induced experimental COPD. Using metabolomics analysis, we further established that treatment with taurine and 3-methyladenine completely restored mitochondrial gene expression levels, thereby ameliorating the PM-induced emphysema. Our studies suggest a potential therapeutic intervention for the C/EBPα/mitochondria/autophagy axis in PM-induced COPD.

Knockdown of c‑Myc activates Fas-mediated apoptosis and sensitizes A549 cells to radiation

Several studies have demonstrated that cancer radiosensitivity is associated with the deregulation of c‑Myc, but the relationship between c‑Myc and Fas in radioresistance of lung adenocarcinoma remains unclear. In this study, we established radiation-resistant A549 cell model (A549/R), and investigated the roles of c‑Myc and Fas in radiation-induced cytotoxicity of A549 cells. Apoptosis detection showed that there were fewer apoptotic cells in A549/R cells treated with radiation than in A549 cells. Western blotting results demonstrated the inverse expression pattern of c‑Myc and Fas in A549 and A549/R cells. Suppression of c‑Myc expression by small interfering RNA (siRNA) displayed enhancement of Fas-mediated apoptosis in A549/R cells, accompanying a significant decrease of Bid, Bcl‑2, pro‑caspase‑8, -9 and -3 and increase of Bax. In contrast, Fas-mediated apoptosis was attenuated while Fas expression was suppressed by ectopic expression of c‑Myc in A549 cells. Moreover, decreased cell viability and increased induction of apoptosis were observed in A549/R cells followed by combinational treatment of c‑Myc siRNA and irradiation, whereas, upregulation of c‑Myc reduced the sensitivity of A549 cells to irradiation. These results indicated that c‑Myc and Fas regulated the sensitivity of A549 cells to irradiation by regulating caspase‑8-mediated Bid activation and the subsequent association with the mitochondrial pathway of apoptosis.

Chromosome 21-Encoded microRNAs (mRNAs): Impact on Down's Syndrome and Trisomy-21 Linked Disease

Down's syndrome (DS; also known as trisomy 21; T21) is caused by a triplication of all or part of human chromosome 21 (chr21). DS is the most common genetic cause of intellectual disability attributable to a naturally-occurring imbalance in gene dosage. DS incurs huge medical, healthcare, and socioeconomic costs, and there are as yet no effective treatments for this incapacitating human neurogenetic disorder. There is a remarkably wide variability in the 'phenotypic spectrum' associated with DS; the progression of symptoms and the age of DS onset fluctuate, and there is further variability in the biophysical nature of the chr21 duplication. Besides the cognitive disruptions and dementia in DS patients other serious health problems such as atherosclerosis, altered lipogenesis, Alzheimer's disease, amyotrophic lateral sclerosis (Lou Gehrig's disease), autoimmune disease, various cancers including lymphoma, leukemia, glioma and glioblastoma, status epilepticus, congenital heart disease, hypotonia, manic depression, prostate cancer, Usher syndrome, motor disorders, Hirschsprung disease, and various physical anomalies such as early aging occur at elevated frequencies, and all are part of the DS 'phenotypic spectrum.' This communication will review the genetic link between these fore-mentioned diseases and a small group of just five stress-associated microRNAs (miRNAs)-that include let-7c, miRNA-99a, miRNA-125b, miRNA-155, and miRNA-802-encoded and clustered on the long arm of human chr21 and spanning the chr21q21.1-chr21q21.3 region.

let-7b and let-7c microRNAs promote histone H2B ubiquitylation and inhibit cell migration by targeting multiple components of the H2B deubiquitylation machinery

Monoubiquitylation of histone H2B (H2Bub1) is catalyzed mainly by the RNF20/RNF40 complex and erased by multiple deubiquitylating enzymes (DUBs). H2Bub1 influences many aspects of chromatin function, including transcription regulation and DNA repair. Cancer cells often display reduced levels of H2Bub1, and this reduction may contribute to cancer progression. The let-7 family of microRNAs comprises multiple members with reported tumor suppressive features, whose expression is frequently downregulated in cancer. We now report that let-7b and let-7c can positively regulate cellular H2Bub1 levels. Overexpression of let-7b and let-7c in a variety of non-transformed and cancer-derived cell lines results in H2Bub1 elevation. The positive effect of let-7b and let-7c on H2Bub1 levels is achieved through targeting of multiple mRNAs, coding for distinct components of the H2B deubiquitylation machinery. Specifically, let-7b and let-7c bind directly and inhibit the mRNAs encoding the DUBs USP42 and USP44, and also the mRNA encoding the adapter protein ATXN7L3, which is part of the DUB module of the SAGA complex. RNF20 knockdown strongly reduces H2Bub1 levels and increases the migration of non-transformed mammary epithelial cells and breast cancer-derived cells. Remarkably, overexpression of let-7b, which partly counteracts the effect of RNF20 knockdown on H2Bub1 levels, also reverses the pro-migratory effect of RNF20 knockdown. Likewise, ATXN7L3 knockdown also increases H2Bub1 levels and reduces cell migration, and this anti-migratory effect is abolished by simultaneous knockdown of RNF20. Together, our findings uncover a novel function of let-7 microRNAs as regulators of H2B ubiquitylation, suggesting an additional mechanism whereby these microRNAs can exert their tumor suppressive effects.

MiR-320a effectively suppresses lung adenocarcinoma cell proliferation and metastasis by regulating STAT3 signals

MicroRNAs play important roles in tumorigenesis of various types of cancers. MiR-320a can inhibits cell proliferation of some cancers, but the biologic roles of miR-320a in lung cancer need to be further studied. Here, we investigated the roles of miR-320a in suppressing the proliferation of lung adenocarcinoma cells. MiR-320a treatment was found to effectively suppress LTEP-a-2 and A549 cell proliferation, and induce more apoptotic cells with irradiation treatment compared with control treatment. Our results also showed that miR-320a, as a novel miRNA, directly regulated signal transducer and activator of transcription 3 (STAT3) and its signals, such as Bcl^-2, Bax, and Caspase 3. The siRNA-inhibited STAT3 levels further proved its roles in regulating STAT3 signals. Moreover, miR-320a treatment effectively suppressed cancer cell growth in mice xenografts compared with controls, and significantly inhibited cell migration in vitro and in vivo. Our findings collectively demonstrated that miR-320a, by directly regulating STAT3 signals, not only suppressed cell proliferation and metastasis, but also enhanced irradiation-induced apoptosis of adenocarcinomia cells.

Smad3-related miRNAs regulated oncogenic TRIB2 promoter activity to effectively suppress lung adenocarcinoma growth

MicroRNAs (miRNAs) and Smad3, as key transcription factors in transforming growth factor-β1 (TGF-β1) signaling, help regulate various physiological and pathological processes. We investigated the roles of Smad3-regulated miRNAs with respect to lung adenocarcinoma cell apoptosis, proliferation, and metastasis. We observed that Smad3 and phospho-SMAD3 (p-Smad3) were decreased in miR-206- (or miR-140)-treated cells and there might be a feedback loop between miR-206 (or miR-140) and TGF-β1 expression. Smad3-related miRNAs affected tribbles homolog 2 (TRIB2) expression by regulating trib2 promoter activity through the CAGACA box. MiR-206 and miR-140 inhibited lung adenocarcinoma cell proliferation in vitro and in vivo by suppressing p-Smad3/Smad3 and TRIB2. Moreover, lung adenocarcinoma data supported a suppressive role for miR-206/miR-140 and an oncogenic role for TRIB2—patients with higher TRIB2 levels had poorer survival. In summary, miR-206 and miR-140, as tumor suppressors, induced lung adenocarcinoma cell death and inhibited cell proliferation by modifying oncogenic TRIB2 promoter activity through p-Smad3. MiR-206 and miR-140 also suppressed lung adenocarcinoma cell metastasis in vitro and in vivo by regulating EMT-related factors.

TRIB2 and the ubiquitin proteasome system in cancer

Tribbles family of pseudokinase proteins are known to mediate the degradation of target proteins in Drosophila and mammalian systems. The main protein proteolysis pathway in eukaryotic cells is the ubiquitin proteasome system (UPS). The tribbles homolog 2 (TRIB2) mammalian family member has been well characterized for its role in murine and human leukaemia, lung and liver cancer. One of the most characterized substrates for TRIB2-mediated degradation is the myeloid transcription factor CCAAT enhancer binding protein α (C/EBPα). However, across a number of cancers, the molecular interactions that take place between TRIB2 and factors involved in the UPS are varied and have differential downstream effects. This review summarizes our current knowledge of these interactions and how this information is important for our understanding of TRIB2 in cancer.

TRIB2 regulates normal and stress-induced thymocyte proliferation

TRIB2, a serine/threonine pseudokinase identified as an oncogene, is expressed at high levels in the T-cell compartment of hematopoiesis. The proliferation of developing thymocytes is tightly controlled to prevent leukemic transformation of T cells. Here we examine Trib2 loss in murine hematopoiesis under steady state and proliferative stress conditions, including genotoxic and oncogenic stress. Trib2^−/− developing thymocytes show increased proliferation, and Trib2^−/− mice have significantly higher thymic cellularity at steady state. During stress hematopoiesis, Trib2^−/− developing thymocytes undergo accelerated proliferation and demonstrate hypersensitivity to 5-fluorouracil (5-FU)-induced cell death. Despite the increased cell death post 5-FU-induced proliferative stress, Trib2^−/− mice exhibit accelerated thymopoietic recovery post treatment due to increased cell division kinetics of developing thymocytes. The increased proliferation in Trib2^−/− thymocytes was exacerbated under oncogenic stress. In an experimental murine T-cell acute lymphoblastic leukemia (T-ALL) model, Trib2^−/− mice had reduced latency in vivo, which associated with impaired MAP kinase (MAPK) activation. High and low expression levels of Trib2 correlate with immature and mature subtypes of human T-ALL, respectively, and associate with MAPK. Thus, TRIB2 emerges as a novel regulator of thymocyte cellular proliferation, important for the thymopoietic response to genotoxic and oncogenic stress, and possessing tumor suppressor function.

JMJD1A promotes tumorigenesis and forms a feedback loop with EZH2/let-7c in NSCLC cells

Lung cancer is the most common cause of cancer-related deaths worldwide, and non-small cell lung cancer (NSCLC) accounts for 80 to 85 % of all lung cancer. Although the standard treatment regimen has been established, long-term survival for NSCLC patients is still generally poor. The histone demethylase Jumonji domain containing 1A (JMJD1A) has been proposed as an oncogene in several types of human cancer, but its clinical significance and functional roles in NSCLC remain largely unclear. In the present study, JMJD1A was frequently upregulated in NSCLC compared with para-carcinoma tissues. JMJD1A knockdown significantly inhibited NSCLC cell growth, migration, and invasion in vitro and tumorigenesis in vivo. Further experiments demonstrated that JMJD1A knockdown could decrease the expression of EZH2, which has been shown to play a crucial role in the carcinogenesis of NSCLC and, in turn, increase the expression of anti-tumor microRNA let-7c. Also, let-7c directly targeted the 3'-untranslated regions of JMJD1A and EZH2. Taken together, JMJD1A could promote NSCLC tumorigenesis. JMJD1A/EZH2/let-7c constituted a feedback loop and might represent a promising therapeutic target for NSCLC.

High glucose concentration induces endothelial cell proliferation by regulating cyclin-D2-related miR-98

Cyclin D2 is involved in the pathology of vascular complications of type 2 diabetes mellitus (T2DM). This study investigated the role of cyclin‐D2‐regulated miRNAs in endothelial cell proliferation of T2DM. Results showed that higher glucose concentration (4.5 g/l) significantly promoted the proliferation of rat aortic endothelial cells (RAOECs), and significantly increased the expression of cyclin D2 and phosphorylation of retinoblastoma 1 (p‐RB1) in RAOECs compared with those under low glucose concentration. The cyclin D2‐3′ untranslated region is targeted by miR‐98, as demonstrated by miRNA analysis software. Western blot also confirmed that cyclin D2 and p‐RB1 expression was regulated by miR‐98. The results indicated that miR‐98 treatment can induce RAOEC apoptosis. The suppression of RAOEC growth by miR‐98 might be related to regulation of Bcl‐2, Bax and Caspase 9 expression. Furthermore, the expression levels of miR‐98 decreased in 4.5 g/l glucose‐treated cells compared with those treated by low glucose concentration. Similarly, the expression of miR‐98 significantly decreased in aortas of established streptozotocin (STZ)‐induced diabetic rat model compared with that in control rats; but cyclin D2 and p‐RB1 levels remarkably increased in aortas of STZ‐induced diabetic rats compared with those in healthy control rats. In conclusion, this study demonstrated that high glucose concentration induces cyclin D2 up‐regulation and miR‐98 down‐regulation in the RAOECs. By regulating cyclin D2, miR‐98 can inhibit human endothelial cell growth, thereby providing novel therapeutic targets for vascular complication of T2DM.

Expression profile of microRNAs in gastrointestinal stromal tumors revealed by high throughput quantitative RT-PCR microarray

AIM: To investigate the microRNA (miRNA) expression profile in gastrointestinal stromal tumor (GIST) tissues that could serve as a novel diagnostic biomarker for GIST detection.

METHODS: We performed a quantitative real-time quantitative reverse transcriptase polymerase chain reaction assay to analyze the expression of 1888 miRNAs in a sample set that included 54 GIST tissue samples.

RESULTS: We found that dysregulation of several miRNAs may be related to the malignant potential of GISTs. Six of these miRNAs, hsa-let-7c, miR-218, miR-488#, miR-4683, miR-34c-5p and miR-4773, were selected as the final list of biomarkers to separate the malignant GISTs (M group) from the benign GISTs (B group). In addition, MiR-29b-2#, hsa-let-7c, miR-891b, miR-218, miR-204, miR-204-3p, miR-628-5p, miR-744, miR-29c#, miR-625 and miR-196a were used to distinguish between the borderline (BO group) and M groups. There were 11 common miRNAs selected to separate the benign and borderline (BB) group from the M group, including hsa-let-7c, miR-218, miR-628-5p, miR-204-3p, miR-204, miR-891b, miR-488#, miR-145, miR-891a, miR-34c-5p and miR-196a.

CONCLUSION: The identified miRNAs appear to be novel biomarkers to distinguish malignant from benign GISTs, which may be helpful to understand the mechanisms of GIST oncogenesis and progression, and to further elucidate the characteristics of GIST subtypes.

miR-126 inhibits cell proliferation and induces cell apoptosis of hepatocellular carcinoma cells partially by targeting Sox2

Hepatocellular carcinoma (HCC) is the fifth most common malignancy and the third leading cause of cancer-related death globally. MicroRNAs (miRNAs) represent a new cohort of gene regulators. Currently, a large number of miRNAs have been reported to be associated with the initiation and maintenance of HCC. Through evaluating the relative concentrations of HCC-associated circulating miRNAs, underexpression of miR-126 has been identified in the blood of HCC patients. However, the exact function of miR-126 on HCC cellular biology progression and relative mechanisms were unclear. In this paper, we explored the function of miR-126 on HCC cells through exogenously transfecting HCC cells with miR-126 mimic. Restored miR-126 expression inhibited cell proliferation, arrest cell cycle progression, and induced cell apoptosis of HepG2 HCC cells. Moreover, to explore the mechanism of miR-126-mediated tumor suppression, we searched the putative targets of miR-126 using prediction program. Surprisingly, we found that sex-determining region Y-box 2 (Sox2) was a putative target gene of miR-126. Further luciferase assays, mRNA and protein assays consistently validated the target role of Sox2. Through restoring the expression of Sox2 in miR-126-transfected HepG2 cells, we found that overexpression of Sox2 could partially abrogate the miR-126-mediated suppression of cell growth. Thus, our data identified miR-126 as a tumor suppressor in HCC through, at least partially by targeting Sox2. This may provide novel diagnostic and therapeutic options for human HCC in future.

Reduced expression levels of let-7c in human breast cancer patients

Circulating microRNAs (miRNAs) are important in the diagnosis of a number of diseases, since serum or plasma miRNAs are more stable compared with miRNA isolated from blood samples. The aim of the present study was to investigate the association between the expression levels of serum let-7c miRNA and the clinical diagnosis of breast cancer (BC). The circulating let-7c levels of 90 BC patients and 64 healthy controls were determined by performing a reverse transcription-quantitative polymerase chain reaction assay. The results demonstrated that let-7c expression was downregulated in the BC tissues compared with the paracarcinoma control tissues. In addition, the let-7c expression in the serum of BC patients was significantly lower compared with the healthy controls (P<0.01). Using a cutoff value of 0.374×10³ copies/ml, the serum expression levels of let-7c exhibited 87.5% sensitivity and 78.9% specificity for distinguishing BC patients from healthy controls (area under the receiver operating characteristic curve, 0.848; 95% confidence interval, 0.785-0.911). Furthermore, the results demonstrated that the serum expression levels of let-7c were significantly higher in premenopausal compared with postmenopausal patients (P<0.05), supporting the hypothesis that postmenopausal status may affect the serum expression levels of let-7c. However, no statistically significant differences were detected in the serum levels of let-7c between ER (or PR)-positive and -negative patients. Therefore, the current study hypothesized that serum let-7c may be used as a novel and valuable biomarker for the diagnosis of BC.

microRNAs and cancer metabolism reprogramming: the paradigm of metformin

Increasing evidence witnesses that cancer metabolism alterations represent a critical hallmark for many types of human tumors. There is a strong need to understand and dissect the molecular mechanisms underlying cancer metabolism to envisage specific biomarkers and underpin critical molecular components that might represent novel therapeutic targets. One challenge, that is the focus of this review, is the reprogramming of the altered metabolism of a cancer cell toward that of un-transformed cell. The anti-hyperglicemic agent, metformin has proven to be effective in reprogramming the metabolism of cancer cells even from those subpopulations endowed with cancer stem like features and very high chemoresistenace to conventional anticancer treatments. A functional interplay involving selective modulation of microRNAs (miRNAs) takes place along the anticancer metabolic effects exerted by metformin. The implications of this interplay will be also discussed in this review.

Integration of mRNA expression profile, copy number alterations, and microRNA expression levels in breast cancer to improve grade definition

Defining the aggressiveness and growth rate of a malignant cell population is a key step in the clinical approach to treating tumor disease. The correct grading of breast cancer (BC) is a fundamental part in determining the appropriate treatment. Biological variables can make it difficult to elucidate the mechanisms underlying BC development. To identify potential markers that can be used for BC classification, we analyzed mRNAs expression profiles, gene copy numbers, microRNAs expression and their association with tumor grade in BC microarray-derived datasets. From mRNA expression results, we found that grade 2 BC is most likely a mixture of grade 1 and grade 3 that have been misclassified, being described by the gene signature of either grade 1 or grade 3. We assessed the potential of the new approach of integrating mRNA expression profile, copy number alterations, and microRNA expression levels to select a limited number of genomic BC biomarkers. The combination of mRNA profile analysis and copy number data with microRNA expression levels led to the identification of two gene signatures of 42 and 4 altered genes (FOXM1, KPNA4, H2AFV and DDX19A) respectively, the latter obtained through a meta-analytical procedure. The 42-based gene signature identifies 4 classes of up- or down-regulated microRNAs (17 microRNAs) and of their 17 target mRNA, and the 4-based genes signature identified 4 microRNAs (Hsa-miR-320d, Hsa-miR-139-5p, Hsa-miR-567 and Hsa-let-7c). These results are discussed from a biological point of view with respect to pathological features of BC. Our identified mRNAs and microRNAs were validated as prognostic factors of BC disease progression, and could potentially facilitate the implementation of assays for laboratory validation, due to their reduced number.

Tumor suppressor microRNAs: a novel non-coding alliance against cancer

Tumor initiation and progression are the outcomes of a stepwise accumulation of genetic alterations. Among these, gene amplification and aberrant expression of oncogenic proteins, as well as deletion or inactivation of tumor suppressor genes, represent hallmark steps. Mounting evidence collected over the last few years has identified different populations of non-coding RNAs as major players in tumor suppression in almost all cancer types. Elucidating the diverse molecular mechanisms underlying the roles of non-coding RNAs in tumor progression might provide illuminating insights, potentially able to assist improved diagnosis, better staging and effective treatments of human cancers. Here we focus on several groups of tumor suppressor microRNAs, whose downregulation exerts a profound oncologic impact and might be harnessed for the benefit of cancer patients.