miRNA expression and its clinical implications for the prevention and diagnosis of non-small-cell lung cancer

Cell cycle associated miRNAs as target and therapeutics in lung cancer treatment

Lung cancer is the primary cause of cancer related deaths worldwide. Limited therapeutic options and resistance to existing drugs are the major hindrances to the clinical success of this cancer. In the past decade, several studies showed the role of microRNA (miRNA) driven cell cycle regulation in lung cancer progression. Therefore, these small nucleotide molecules could be utilized as promising tools in lung cancer therapy. In this review, we highlighted the recent advancements in lung cancer therapy using cell cycle linked miRNAs. By highlighting the roles of the specific cell cycle core regulators affiliated miRNAs in lung cancer, we further outlined how these miRNAs can be explored in early diagnosis and treatment strategies to prevent lung cancer. With the provided information from our review, more medical efforts can ensure a potential breakthrough in miRNA-based lung cancer therapy.

HIF1α-SP1 interaction disrupts the circ-0001875/miR-31-5p/SP1 regulatory loop under a hypoxic microenvironment and promotes non-small cell lung cancer progression

BACKGROUND

Circular RNAs (circRNAs) play an important role in the progression of non-small cell lung cancer (NSCLC), especially under tumor hypoxia. However, the precise functions and underlying mechanisms of dysregulated circRNAs in NSCLC are largely unknown.

METHODS

High-throughput RNA sequencing was performed to identify significantly expressed circRNAs in NSCLC tissues. The functions of circ-0001875 in NSCLC cells were investigated in vitro and in vivo. The regulatory relationships of circ-0001875, miR-31-5p and SP1 were examined by dual luciferase reporter assays and rescue experiments. The signal pathway of epithelial-to-mesenchymal transition and the formation of filopodia were analyzed by western blot and immunofluorescence staining. The binding of SP1 to Alu elements was evaluated by RNA immunoprecipitation, and the HIF1α and SP1 interaction was detected by co-immunoprecipitation.

RESULTS

We identified the novel Has_circ_0001875 as a significantly upregulated circRNA in NSCLC tissues and cell lines. circ-0001875 promoted the proliferation and metastasis of NSCLC both in vitro and in vivo, and induced NSCLC cells to extend filopodia. Mechanistically, circ-0001875 sponged miR-31-5p to regulate SP1, influencing epithelial-to-mesenchymal transition via the TGFβ/Smad2 signal pathway. SP1 negatively regulated circ-0001875 formation through an AluSq-dependent feedback loop, which was disrupted by competitive binding of HIF1α to SP1 under hypoxia condition. The circ-0001875/miR-31-5p/SP1 axis was associated with the clinical features and prognosis of NSCLC patients.

CONCLUSIONS

Our results revealed that the circ-0001875/miR-31-5p/SP1 axis and the complex regulatory loops influence NSCLC progression. These findings provide new insights into the regulation of circRNA formation under tumor hypoxia.

DICER-AS1 functions as competing endogenous RNA that targets CSR1 by sponging microRNA-650 and suppresses gastric cancer progression

OBJECTIVE

This study explored the functional interactions between the long non-coding RNA DICER-AS1 and the cellular stress response 1 (CSR1) gene in gastric cancer.

METHODS

Quantitative polymerase chain reaction (qPCR) and western blotting were used to measure DICER-AS1, CSR1, and miR-650 expression levels. Gastric cancer cell line proliferation and migration abilities were analyzed using the MTT and transwell migration and invasion assays, respectively. Bioinformatic analysis and dual luciferase reporter assays were employed to study the functional interactions among miR-650, DICER-AS1, and CSR1.

RESULTS

DICER-AS1 and CSR1 expression levels were significantly decreased in gastric cancer tissues compared with normal tissues, and qPCR analysis showed that miR-650 was upregulated in gastric cancer tissues. Bioinformatic analysis and dual luciferase reporter assays revealed that DICER-AS1 functioned as a competing endogenous RNA that sponged miR-650, which in turn regulated CSR1 expression. Importantly, ectopic DICER-AS1 and CSR1 expression inhibited cell proliferation and migration in vitro and suppressed xenograft tumorgenicity in vivo.

CONCLUSIONS

These results suggest that DICER-AS1 functions as a competing endogenous RNA that regulates miR-650 to suppress proliferation and migration of gastric cancer cells by targeting CSR1. These findings indicate that targeting DICER-AS1 and miR-650 could be a novel treatment for gastric cancer.

MicroRNA-422a functions as a tumor suppressor in non-small cell lung cancer through SULF2-mediated TGF-β/SMAD signaling pathway

MicroRNAs (miRNAs) have been demonstrated to participate in a variety of human cancers by functioning as post-transcriptional regulators of oncogenes or antioncogenes including non-small cell lung cancer (NSCLC). The aim of the current study was to identify the role of miR-422a in NSCLC via sulfatase 2 (SULF2) to further elucidate the mechanism of NSCLC. Initially, the expression of miR-422a and SULF2 was determined in NSCLC tissues and cells. The role of miR-422a in NSCLC was identified in relation with a miR-422a mimic or inhibitor, siRNA against SULF2 and TGF-β1. The regulatory effects of miR-422a were examined following detection of the related epithelial mesenchymal transition (EMT)-related genes, and the apoptosis-related genes and evaluation of their cellular biological functions. The expression pattern of miR-422a, SULF2, and the TGF-β/SMAD pathway-related genes was detected to elucidate the mechanism by which miR-422a influences the progression of NSCLC. Finally, xenograft tumors in nude mice were observed for tumorigenicity evaluation purposes. Our results showed that miR-422a was poorly expressed while SULF2 was highly expressed in NSCLC. Dual luciferase reporter gene assay further verified that miR-422a targeted SULF2. Altogether, this study demonstrated that miR-422a downregulated SULF2 to inhibit the TGF-β/SMAD pathway. NSCLC cell proliferation, migration, invasion, colony formation, EMT and tumorigenesis were all inhibited while apoptosis was promoted upon restoration of miR-422a or silencing of SULF2. However, the activation of the TGF-β/SMAD pathway was determined to reverse the tumor-suppressive effects of si-SULF2. miR-422a restoration, which ultimately inhibited the progression of NSCLC by suppressing the TGF-β/SMAD pathway via SULF2.

microRNA-612 suppresses the malignant development of non-small-cell lung cancer by directly targeting bromodomain-containing protein 4

Background: Aberrant expression of microRNAs (miRNAs) in non-small-cell lung cancer (NSCLC) has been reported. Dysregulation of miRNAs exerts tumor-suppressing or tumor-promoting actions on the pathology and biological behaviors of NSCLC. miR-612 is associated with many types of human cancer; however, the expression, potential roles, and regulatory mechanisms of miR-612 in NSCLC remain unclear.

Material and methods: Here, the expression level of miR-612 in NSCLC tissue specimens and a panel of cell lines were evaluated by RT-qPCR. Cell-Counting Kit 8, flow cytometry, Transwell migration and invasion, and in vivo tumor growth assays were performed to determine the functional role of miR-612 in malignant phenotypes of NSCLC cells. The molecular mechanism underlying the tumor-suppressive roles of miR-612 in NSCLC was investigated.

Results: miR-612 was expressed at low levels in NSCLC, and low miR-612 expression was significantly correlated with TNM stage and lymph node metastasis. NSCLC patients with low miR-612 expression had shorter overall survival rate than those with high levels. Exogenous miR-612 expression decreased proliferation, migration, and invasion, and promoted apoptosis of NSCLC cells in vitro. miR-612 upregulation hindered NSCLC tumor growth in vivo. Bromodomain-containing protein 4 (BRD4) was confirmed as a direct target gene of miR-612 in NSCLC cells. BRD4 was obviously overexpressed in human NSCLC tissues and inverse correlated with miR-612 expression. Inhibition of BRD4 expression simulated the tumor-suppressive functions of miR-612 overexpression in NSCLC cells. Reintroduction of miR-612 expression abrogated the miR-612-mediated suppressive effects on NSCLC cells. BRD4 upregulation inhibited activation of the PI3K/Akt pathway in NSCLC cells in vitro and in vivo.

Conclusion: This study supports the first evidence that miR-612 exerts tumor-suppressive roles in the aggressive behaviors of NSCLC cells in vitro and in vivo through direct targeting BRD4 and deactivating the PI3K/Akt pathway. Thus, miR-612 might be a promising target for anticancer therapies in patients with NSCLC.

MiR-138-5p suppresses lung adenocarcinoma cell epithelial-mesenchymal transition, proliferation and metastasis by targeting ZEB2

BACKGROUND

MiR-138-5p is regarded as a tumour suppressor in many cancers. Transforming growth factor beta (TGF-β) often acts as a tumor promotor at the late stages of human cancers. However, the function of miR-138-5p on lung adenocarcinoma cells induced by TGF-β remains to be further confirmed.

METHODS

RT-qPCR was used to detect the expression of human lung adenocarcinoma tissues, adjacent normal tissues, and relative cell lines. When the lung adenocarcinoma cells A549 and H1299 were transfected with negative control (NC), miR-138-5p mimics and miR-138-5p inhibitor by lipofectamine3000 and treated with or without TGF-β1, the lung adenocarcinoma cell function was detected by Immunofluorescence, Western blotting (WB), cell counting Kit-8 (CCK8), colony formation, EdU, Wound-healing and Transwell assays. The relation between miR-138-5p and zinc finger E-box-binding homeobox 2 (ZEB2) was detected by RT-qPCR, WB, and Luciferase reporter assays. When ZEB2 was knocked down, the lung adenocarcinoma cell function was detected by WB, CCK8 and Transwell assays.

RESULTS

The expression of miR-138-5p was decreased in lung adenocarcinoma tissues and cell lines. When treated with or without TGF-β1, overexpression of miR-138-5p suppressed EMT, proliferation and metastasis of A549 and H1299. ZEB2 was verified as the direct target of miR-138-5p. Downregulation of ZEB2 suppressed EMT, proliferation and metastasis of lung adenocarcinoma cell, which could be reversed by miR-138-5p inhibitor.

CONCLUSIONS

MiR-138-5p inhibits epithelial-mesenchymal transition, growth and metastasis of lung adenocarcinoma cells through targeting ZEB2.

Non-coding RNAs as emerging regulators of epithelial to mesenchymal transition in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) remains a major health problem that patients suffer from around the world. The epithelial to mesenchymal transition (EMT) has attractive roles in increasing malignant potential and reducing sensitivity to conventional therapeutics in NSCLC cells. Meanwhile, it is now evident that non-coding RNAs (ncRNAs), primarily microRNAs and long non-coding RNAs contribute to tumorigenesis partially via regulating EMT. This article briefly summarizes current researches about EMT-related ncRNAs in NSCLC and discusses their crucial roles in the complex regulatory network. Also, the authors will show the evidence that ncRNAs not only contribute to cancer cells migration and invasion, but also take charge of the resistance of chemotherapy, radiotherapy and EGFR-TIKs. Then, we will further discuss the potential of inhibition of EMT via manipulating relevant ncRNAs to change our current treatment of NSCLC patients.

The Role of Epigenomics in the Study of Cancer Biomarkers and in the Development of Diagnostic Tools

Epigenetics plays a key role in cancer development. Genetics alone cannot explain sporadic cancer and cancer development in individuals with no family history or a weak family history of cancer. Epigenetics provides a mechanism to explain the development of cancer in such situations. Alterations in epigenetic profiling may provide important insights into the etiology and natural history of cancer. Because several epigenetic changes occur before histopathological changes, they can serve as biomarkers for cancer diagnosis and risk assessment. Many cancers may remain asymptomatic until relatively late stages; in managing the disease, efforts should be focused on early detection, accurate prediction of disease progression, and frequent monitoring. This chapter describes epigenetic biomarkers as they are expressed during cancer development and their potential use in cancer diagnosis and prognosis. Based on epigenomic information, biomarkers have been identified that may serve as diagnostic tools; some such biomarkers also may be useful in identifying individuals who will respond to therapy and survive longer. The importance of analytical and clinical validation of biomarkers is discussed, along with challenges and opportunities in this field.

Exosomal miRNAs as biomarkers of recurrent lung cancer

Prognosis of lung cancer still remains grim largely due to recurrence and aggressive metastasis of the disease. In this study, we examined the potential of exosomal miRNAs as biomarkers of recurrent lung cancer. Initially, in vitro miRNA profiles of normal lung (Beas-2b) and lung cancer (H1299) cells and of exosomes isolated from conditioned media were determined. In vivo study involved establishing subcutaneous primary and recurrent lung cancer xenografts in nude mouse model and examining tumor and serum exosomal miRNA alteration in secondary/recurrent lung tumors. A total of 77 miRNAs were observed to be significantly modulated in the H1299 cells (47 miRNA upregulated and 30 downregulated) compared to the Beas-2b cells. The exosomes isolated from conditioned media indicated several miRNAs which were in agreement with cells of origin. A similarity was also observed between miRNAs from serum exosomes and tumors, indicating their origin from the lung tumors. Two miRNAs, miR-21 and miR-155, were found to be significantly upregulated in recurrent tumors compared to primary tumors. These miRNAs were also upregulated in serum exosomes of recurrent tumor-bearing animals versus non-tumor- or primary tumor-bearing animals. Increased expression of the recurrent disease markers were also observed in recurrent tumors compared with primary tumors. Serum exosomes from recurrent tumor mice mirrored its tumor profile in expressing higher levels of these proteins compared with exosomes from primary tumor mice. Our data suggest that exosomal miRNA signatures may be a true representation of a pathological profile of lung cancer; thus, miRNAs could serve as promising biomarkers for non-invasive diagnosis of the disease.

Polymorphisms in MicroRNAs are associated with survival in non-small cell lung cancer

BACKGROUND

MicroRNAs (miRNA) play important roles in the regulation of eukaryotic gene expression and are involved in human carcinogenesis. Single-nucleotide polymorphisms (SNP) in miRNA sequence may alter miRNA functions in gene regulation, which, in turn, may affect cancer risk and disease progression.

METHODS

We conducted an analysis of associations of 142 miRNA SNPs with non-small cell lung cancer (NSCLC) survival using data from a genome-wide association study (GWAS) in a Caucasian population from the Massachusetts General Hospital (Boston, MA) including 452 early-stage and 526 late-stage NSCLC cases. Replication analyses were further performed in two external populations, one Caucasian cohort from The University of Texas MD Anderson Cancer Center (Houston, TX) and one Han Chinese cohort from Nanjing, China.

RESULTS

We identified seven significant SNPs in the discovery set. Results from the independent Caucasian cohort demonstrated that the C allele of rs2042253 (hsa-miRNA-5197) was significantly associated with decreased risk for death among the patients with late-stage NSCLC (discovery set: HR, 0.80; P = 0.007; validation set: HR, 0.86; P = 0.035; combined analysis: HR, 0.87; P = 0.007).

CONCLUSIONS

These findings provide evidence that some miRNA SNPs are associated with NSCLC survival and can be used as predictive biomarkers.

IMPACT

This study provided an estimate of outcome probability for survival experience of patients with NSCLC, which demonstrates that genetic factors, as well as classic nongenetic factors, may be used to predict individual outcome.

MicroRNA-574-5p was pivotal for TLR9 signaling enhanced tumor progression via down-regulating checkpoint suppressor 1 in human lung cancer

Accumulating data suggested that functional expression of Toll-like receptors (TLRs) in tumor cells was involved in tumor progression. Our previous study demonstrated that TLR9 signaling could enhance the tumor progression of human lung cancer cells in vitro and in vivo. We further showed that miR-574-5p was the mostly up-regulated miRNA in human lung cancer cells under TLR9 signaling by miRNA array analysis. Here we characterized the potential role of miRNA-574-5p in enhanced tumor progression induced by TLR9 signaling in human lung cancer. We confirmed that TLR9 signaling effectively elevated the expression of miR-574-5p in human lung cancer cells. Notably, we found that down-regulation of miRNA-574-5p using miR-574-5p inhibitor in vitro or miR-574-5p sponge in vivo significantly abrogated the enhanced tumor progression induced by TLR9 signaling. Further studies showed that miR-574-5p was an important player associated with enhanced tumor progression of human lung cancer cells. Notably, we identified checkpoint suppressor 1 (Ches1) as the dominant direct target for miRNA-574-5p to confer the TLR9 signaling enhanced tumor progression. We revealed that over-expression of Ches1 significantly inhibited the cell cycle entry of human lung cancer cells. Finally, we revealed that the expression of miR-574-5p was positively correlated with TLR9 and reversely correlated with Ches1 in lung cancer patients. Our findings not only facilitated the further understanding of the crosstalk between miRNAs and TLRs in tumor biology, but also provided novel potential candidates for treatment of cancer.

MicroRNAs involved in regulating epithelial-mesenchymal transition and cancer stem cells as molecular targets for cancer therapeutics

One of the major challenges in cancer gene therapy is the identification of functionally relevant tumor-specific genes as the therapeutic targets. MicroRNAs (miRNAs) are a class of small, 22-25 nucleotides, endogenously expressed noncoding RNA. miRNAs are important genetic regulators: one miRNA can possibly target multiple genes and they can function as tumor promoters (oncogenic miRNAs, oncomirs) or tumor suppressors (anti-oncomirs). Therefore, the identification of misregulated miRNAs in cellular signaling pathways related to oncogenesis can have profound implications for cancer therapy. The epithelial-mesenchymal transition (EMT) converts epithelial cells into mesenchymal cells, a normal embryological process that frequently get activated during cancer invasion and metastasis. Recent evidence also supports the presence of a small subset of self-renewing, stem-like cells within the tumor mass that possess the capacity to seed new tumors and they have been termed 'cancer stem cells (CSC)'. Conceivably, these CSCs could provide a resource for cells that cause therapy resistance. Although the cell origin of CSCs remains to be fully elucidated, a growing body of evidence has demonstrated that the biology of EMT and CSCs is tightly linked with the sequences and compositions of miRNA molecules. Therefore, targeting miRNAs involved in EMT and CSCs regulation can provide novel miRNA-based therapeutic strategies in oncology.

Development of plasmid calibrators for absolute quantification of miRNAs by using real-time qPCR

MicroRNAs (miRNAs) are small noncoding RNAs of approximately 18 to 25 nucleotides in length that negatively regulate gene expression via either the degradation or translational inhibition of their target mRNAs. Because miRNAs are essential for the regulation of critical physiological processes as well as a variety of pathological events, they have emerged as a novel class of molecular diagnostic biomarkers and therapeutic agents or targets. Accordingly, the need for novel methods for the quantification of miRNA has increased due to interest in their clinical implications. Currently, real-time quantitative polymerase chain reaction (qPCR) is considered the most robust technology for nucleic acid quantification. Different tools for miRNA quantification by using qPCR are now commercially available, but only relative quantification strategies have been reported. This situation may be partly due to the difficulty in obtaining an appropriate molecule with which to establish an miRNA calibration range. Here, we describe a rapid and convenient strategy for the development of a calibrator, which enables the absolute quantification of miRNAs by using qPCR and allows the cloning of a synthetic sequence of interest instead of a PCR product into a plasmid.

Polymorphisms in miRNA-binding sites of nucleotide excision repair genes and colorectal cancer risk

Reduced DNA repair capacity and DNA damage accumulation may lead to cancer development. Regulation of and coordination between genes involved in DNA repair pathways is fundamental for maintaining genome stability, and post-transcriptional gene regulation by microRNAs (miRNAs) may therefore be of particular relevance. In this context, the presence of single nucleotide polymorphisms (SNPs) within the 3'untranslated regions of target DNA repair genes could alter the binding with specific miRNAs, modulating gene expression and ultimately affecting cancer susceptibility. In this study, we investigated the role of genetic variations in miRNA-binding sites of nucleotide excision repair (NER) genes in association with colorectal cancer (CRC) risk. From 28 NER genes, we screened among SNPs residing in their 3'untranslated regions and simultaneously located in miRNA-binding sites, with an in silico approach. Through the calculation of different binding free energy according to both alleles of identified SNPs, and with global binding free energies median providing a threshold, we selected nine NER gene variants. We tested those SNPs in 1098 colorectal cancer cases and 1469 healthy controls from the Czech Republic. Rs7356 in RPA2 and rs4596 in GTF2H1 were associated with colorectal cancer risk. After stratification for tumor location, the association of both SNPs was significant only for rectal cancer (rs7356: OR 1.52, 95% CI 1.02-2.26, P = 0.04 and rs4596: OR 0.69, 95% CI 0.50-0.94, P = 0.02; results not adjusted for multiple testing). Variation in miRNA target binding sites in the 3'untranslated region of NER genes may be important for modulating colorectal cancer risk, with a different relevance according to tumor location.

Applications of MicroRNAs in the Diagnosis and Prognosis of Lung Cancer

INTRODUCTION: Lung cancer is the leading cause of cancer death worldwide, due to its late diagnosis and poor outcome. MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression at the posttranscriptional levels by either degrading or blocking translation of messenger RNA targets. Accumulating evidence indicates that miRNAs play a pivotal role in the development and progression of human malignancies, including lung cancer. AREAS COVERED: In this review, the authors focus on 1) application of miRNA-based biomarkers to help classify lung cancer, 2) application of the miRNA biomarkers for the early detection of lung cancer, and 3) use of miRNAs as biomarkers to predict outcomes of lung cancer. EXPERT OPINION: MiRNAs provide promising biomarkers for the diagnosis and prognosis of lung cancer. The developed miRNA biomarkers should be comprehensively and prospectively validated in clinical trials before being used in laboratory settings.