Downregulation of miR-145 contributes to lung adenocarcinoma cell growth to form brain metastases

Brain-Periphery Axes: The Potential Role of Extracellular Vesicles-Delivered miRNAs

Bidirectional communication between the central nervous system (CNS) and peripheral organs and tissue has been widely documented in physiological and pathological conditions. This communication relies on the bilateral transmission of signaling molecules and substances that circulate throughout the body and reach their target site(s) via the blood and other biological fluids (e.g., the cerebrospinal fluid, the lymph). One of the mechanisms by which these molecular messengers are exchanged is through the secretion of extracellular vesicles (EVs). EVs are known to mediate cell-to-cell communication by delivering biological molecules, including nucleic acids, proteins, lipids, and various other bioactive regulators. Moreover, EVs can cross the blood-brain barrier (BBB), enabling direct communication between the periphery and the brain. In particular, the delivery of microRNAs (miRNAs) can modulate the expression profiles of recipient cells, thereby influencing their functions. This review synthesizes current findings about the brain-periphery cross-talk mediated by EVs-delivered miRNAs. Although this mechanism has been definitively shown in a few cases, much evidence indirectly indicates that it could mediate brain-peripherical organs/tissue communication, especially in pathological conditions. Therefore, understanding this process could provide valuable insights for the treatment and management of neurological and systemic diseases.

[Application Research of Serum miR-4646-5p, miR-3654 Combined with Traditional Lung Cancer Tumor Markers in the Diagnosis of Lung Cancer in Xuanwei, Yunnan Province]

BACKGROUND

The incidence rate of lung cancer in Xuanwei has been continuously increasing in recent years, and it also features high incidence across all age groups and high mortality rates among female lung cancer patients. Therefore, the search for more stable biomarkers for the diagnosis of Xuanwei lung cancer holds tremendous clinical application prospects. This study aims to explore the clinical application value of these four microRNAs (miRNAs) individually and in combination with traditional lung cancer tumor markers in the detection and diagnosis of Xuanwei lung cancer.

METHODS

By detecting the expression levels of four miRNAs and five traditional lung cancer tumor markers in the serum of 45 Xuanwei lung cancer patients and healthy physical examination participants, the Logistic regression model was employed to comprehensively evaluate the sensitivity, specificity, diagnostic efficacy, and other relevant statistical indicators of the four miRNAs in the diagnosis of Xuanwei lung cancer.

RESULTS

Among the individual miRNAs, miR-4646-5p and miR-3654 showed significant differences in expression levels between the Xuanwei lung cancer group and the control group (P<0.05). miR-3654 demonstrated the best diagnostic performance with a sensitivity of 86.7%, specificity of 82.2%, and an area under the curve of 0.847. Combining miR-3654 with miR-4646-5p and carcinoembryonic antigen (CEA) resulted in the highest diagnostic efficacy for Xuanwei lung cancer, with a sensitivity of 73.3%, specificity of 93.3%, area under the curve of 0.901, and a positive predictive value of 91.7%.

CONCLUSIONS

Among the four miRNAs, serum miR-3654 exhibits the best diagnostic efficacy for Xuanwei lung cancer. Combined with miR-4646-5p and CEA, its diagnostic value for Xuanwei lung cancer can be effectively enhanced, making it a promising screening indicator for Xuanwei lung cancer.

A Review of Recent Advances in the Molecular Mechanisms Underlying Brain Metastasis in Lung Cancer

Brain metastasis from lung cancer is a prevalent mode of treatment failure associated with a poor prognosis. The incidence of brain metastasis has recently shown a dramatic increase. The early detection and risk stratification of lung cancer-related brain metastasis would be highly advantageous for patients. However, our current knowledge and comprehension of the underlying mechanisms driving brain metastasis in lung cancer pose significant challenges. This review summarizes the mechanisms underlying brain metastasis, focusing on the intricate interplay between lung cancer-derived tumor cells and the unique characteristics of the brain, recent advancements in the identification of driver genes, concomitant genes, epigenetic features, including miRNAs and long noncoding RNAs, as well as the molecular characterization of brain metastasis originating from other organs, which may further enhance risk stratification and facilitate precise treatment strategies.

Exploring the Molecular Tumor Microenvironment and Translational Biomarkers in Brain Metastases of Non-Small-Cell Lung Cancer

Brain metastases represent a significant clinical challenge in the treatment of non-small-cell lung cancer (NSCLC), often leading to a severe decline in patient prognosis and survival. Recent advances in imaging and systemic treatments have increased the detection rates of brain metastases, yet clinical outcomes remain dismal due to the complexity of the metastatic tumor microenvironment (TME) and the lack of specific biomarkers for early detection and targeted therapy. The intricate interplay between NSCLC tumor cells and the surrounding TME in brain metastases is pivotal, influencing tumor progression, immune evasion, and response to therapy. This underscores the necessity for a deeper understanding of the molecular underpinnings of brain metastases, tumor microenvironment, and the identification of actionable biomarkers that can inform multimodal treatment approaches. The goal of this review is to synthesize current insights into the TME and elucidate molecular mechanisms in NSCLC brain metastases. Furthermore, we will explore the promising horizon of emerging biomarkers, both tissue- and liquid-based, that hold the potential to radically transform the treatment strategies and the enhancement of patient outcomes.

The role of microRNAs in brain metastasis

Brain metastasis (BM) is the most common type of brain tumor and frequently foreshadows disease progression and poor overall survival with patients having a median survival of 6 months. 70,000 new cases of BM are diagnosed each year in the United States (US) and the incidence rate for BM is increasing with improved detection. MicroRNAs (miRNAs) are small non-coding RNAs that serve as critical regulators of gene expression and can act as powerful oncogenes and tumor suppressors. MiRNAs have been heavily implicated in cancer and proposed as biomarkers or therapeutic targets or agents. In this review, we summarize an extensive body of scientific work investigating the role of microRNAs in BM. We discuss miRNA dysregulation, functions, targets, and mechanisms of action in BM and present the current standing of miRNAs as biomarkers and potential therapeutics for BM. We conclude with future directions of miRNA basic and clinical research in BM.

Cell-Free miRNAs as Non-Invasive Biomarkers in Brain Tumors

Diagnosing brain tumors, especially malignant variants, such as glioblastoma, medulloblastoma, or brain metastasis, presents a considerable obstacle, while current treatment methods often yield unsatisfactory results. The monitoring of individuals with brain neoplasms becomes burdensome due to the intricate tumor nature and associated risks of tissue biopsies, compounded by the restricted accuracy and sensitivity of presently available non-invasive diagnostic techniques. The uncertainties surrounding diagnosis and the tumor's reaction to treatment can lead to delays in critical determinations that profoundly influence the prognosis of the disease. Consequently, there exists a pressing necessity to formulate and validate dependable, minimally invasive biomarkers that can effectively diagnose and predict brain tumors. Cell-free microRNAs (miRNAs), which remain stable and detectable in human bodily fluids, such as blood and cerebrospinal fluid (CSF), have emerged as potential indicators for a range of ailments, brain tumors included. Numerous investigations have showcased the viability of profiling cell-free miRNA expression in both CSF and blood samples obtained from patients with brain tumors. Distinct miRNAs demonstrate varying expression patterns within CSF and blood. While cell-free microRNAs in the blood exhibit potential in diagnosing, prognosticating, and monitoring treatment across diverse tumor types, they fall short in effectively diagnosing brain tumors. Conversely, the cell-free miRNA profile within CSF demonstrates high potential in delivering precise and specific evaluations of brain tumors.

Advances in Brain Metastases Diagnosis: Non-coding RNAs As Potential Biomarkers

Brain metastasis is considered the most common brain tumor. They arise from different primary cancers. The most common primary tumors giving brain metastases include breast, colorectal, lung, melanoma, and renal cancer. Depending only on history, physical examination, and conventional imaging modalities makes brain tumors diagnosis difficult. Rapid and non-invasive promising modalities could diagnose and differentiate between different brain metastases without exposing the patients to unnecessary brain surgeries for biopsies. One of these promising modalities is non-coding RNAs (ncRNAs). NcRNAs can determine brain metastases' prognosis, chemoresistance, and radioresistance. It also helps us to understand the pathophysiology of brain metastases development. Additionally, ncRNAs may work as potential therapeutic targets for brain metastases treatment and prevention. Herein, we present deregulated ncRNAs in different brain metastases, including microRNAs and long non-coding RNAs (lncRNAs), such as gastric adenocarcinoma, colorectal, breast, melanoma, lung, and prostate cancer. Additionally, we focus on serum and cerebrospinal fluid (CSF) expression of these ncRNAs in patients with brain metastases compared to patients with primary tumors. Moreover, we discuss the role of ncRNAs in modulating the immune response in the brain microenvironment. More clinical studies are encouraged to assess the specificity and sensitivity of these ncRNAs.

Advances in the Molecular Landscape of Lung Cancer Brain Metastasis

Lung cancer is one of the most frequent tumors that metastasize to the brain. Brain metastasis (BM) is common in advanced cases, being the major cause of patient morbidity and mortality. BMs are thought to arise via the seeding of circulating tumor cells into the brain microvasculature. In brain tissue, the interaction with immune cells promotes a microenvironment favorable to the growth of cancer cells. Despite multimodal treatments and advances in systemic therapies, lung cancer patients still have poor prognoses. Therefore, there is an urgent need to identify the molecular drivers of BM and clinically applicable biomarkers in order to improve disease outcomes and patient survival. The goal of this review is to summarize the current state of knowledge on the mechanisms of the metastatic spread of lung cancer to the brain and how the metastatic spread is influenced by the brain microenvironment, and to elucidate the molecular determinants of brain metastasis regarding the role of genomic and transcriptomic changes, including coding and non-coding RNAs. We also present an overview of the current therapeutics and novel treatment strategies for patients diagnosed with BM from NSCLC.

Tumor microenvironment and exosomes in brain metastasis: Molecular mechanisms and clinical application

Metastasis is one of the important biological features of malignant tumors and one of the main factors responsible for poor prognosis. Although the widespread application of newer clinical technologies and their continuous development have significantly improved survival in patients with brain metastases, there is no uniform standard of care. More effective therapeutic measures are therefore needed to improve prognosis. Understanding the mechanisms of tumor cell colonization, growth, and invasion in the central nervous system is of particular importance for the prevention and treatment of brain metastases. This process can be plausibly explained by the “seed and soil” hypothesis, which essentially states that tumor cells can interact with various components of the central nervous system microenvironment to produce adaptive changes; it is this interaction that determines the development of brain metastases. As a novel form of intercellular communication, exosomes play a key role in the brain metastasis microenvironment and carry various bioactive molecules that regulate receptor cell activity. In this paper, we review the roles and prospects of brain metastatic tumor cells, the brain metastatic tumor microenvironment, and exosomes in the development and clinical management of brain metastases.

The Significance of MicroRNAs in the Molecular Pathology of Brain Metastases

Brain metastases are the most frequent intracranial tumors in adults and the cause of death in almost one-fourth of cases. The incidence of brain metastases is steadily increasing. The main reason for this increase could be the introduction of new and more efficient therapeutic strategies that lead to longer survival but, at the same time, cause a higher risk of brain parenchyma infiltration. In addition, the advances in imaging methodology, which provide earlier identification of brain metastases, may also be a reason for the higher recorded number of patients with these tumors. Metastasis is a complex biological process that is still largely unexplored, influenced by many factors and involving many molecules. A deeper understanding of the process will allow the discovery of more effective diagnostic and therapeutic approaches that could improve the quality and length of patient survival. Recent studies have shown that microRNAs (miRNAs) are essential molecules that are involved in specific steps of the metastatic cascade. MiRNAs are endogenously expressed small non-coding RNAs that act as post-transcriptional regulators of gene expression and thus regulate most cellular processes. The dysregulation of these molecules has been implicated in many cancers, including brain metastases. Therefore, miRNAs represent promising diagnostic molecules and therapeutic targets in brain metastases. This review summarizes the current knowledge on the importance of miRNAs in brain metastasis, focusing on their involvement in the metastatic cascade and their potential clinical implications.

Liquid biopsies to occult brain metastasis

Brain metastasis (BrM) is a major problem associated with cancer-related mortality, and currently, no specific biomarkers are available in clinical settings for early detection. Liquid biopsy is widely accepted as a non-invasive method for diagnosing cancer and other diseases. We have reviewed the evidence that shows how the molecular alterations are involved in BrM, majorly from breast cancer (BC), lung cancer (LC), and melanoma, with an inception in how they can be employed for biomarker development. We discussed genetic and epigenetic changes that influence cancer cells to breach the blood-brain barrier (BBB) and help to establish metastatic lesions in the uniquely distinct brain microenvironment. Keeping abreast with the recent breakthroughs in the context of various biomolecules detections and identifications, the circulating tumor cells (CTC), cell-free nucleotides, non-coding RNAs, secretory proteins, and metabolites can be pursued in human body fluids such as blood, serum, cerebrospinal fluid (CSF), and urine to obtain potential candidates for biomarker development. The liquid biopsy-based biomarkers can overlay with current imaging techniques to amplify the signal viable for improving the early detection and treatments of occult BrM.

Cancer driver gene and non-coding RNA alterations as biomarkers of brain metastasis in lung cancer: A review of the literature

Brain metastasis (BM) is the most common event in patients with lung cancer. Despite multimodal treatments and advances in systemic therapies, development of BM remains one of the main factors associated with poor prognosis and mortality in patients with lung cancer. Therefore, better understanding of mechanisms involved in lung cancer brain metastasis (LCBM) is of great importance to suppress cancer cells and to improve the overall survival of patients. Several cancer-related genes such as EGFR and KRAS have been proposed as potential predictors of LCBM. In addition, there is ample evidence supporting crucial roles of non-coding RNAs (ncRNAs) in mediating LCBM. In this review, we provide comprehensive information on risk assessment, predictive, and prognostic panels for early detection of BM in patients with lung cancer. Moreover, we present an overview of LCBM molecular mechanisms, cancer driver genes, and ncRNAs which may predict the risk of BM in lung cancer patients. Recent clinical studies have focused on determining mechanisms involved in LCBM and their association with diagnosis, prognosis, and treatment outcomes. These studies have shown that alterations in EGFR, KRAS, BRAF, and ALK, as the most frequent coding gene alterations, and dysregulation of ncRNAs such as miR-423, miR-330-3p, miR-145, piR-651, and MALAT1 can be considered as potential biomarkers of LCBM.

Differential and Common Signatures of miRNA Expression and Methylation in Childhood Central Nervous System Malignancies: An Experimental and Computational Approach

Epigenetic modifications are considered of utmost significance for tumor ontogenesis and progression. Especially, it has been found that miRNA expression, as well as DNA methylation plays a significant role in central nervous system tumors during childhood. A total of 49 resected brain tumors from children were used for further analysis. DNA methylation was identified with methylation-specific MLPA and, in particular, for the tumor suppressor genes CASP8, RASSF1, MGMT, MSH6, GATA5, ATM1, TP53, and CADM1. miRNAs were identified with microarray screening, as well as selected samples, were tested for their mRNA expression levels. CASP8, RASSF1 were the most frequently methylated genes in all tumor samples. Simultaneous methylation of genes manifested significant results with respect to tumor staging, tumor type, and the differentiation of tumor and control samples. There was no significant dependence observed with the methylation of one gene promoter, rather with the simultaneous presence of all detected methylated genes' promoters. miRNA expression was found to be correlated to gene methylation. Epigenetic regulation appears to be of major importance in tumor progression and pathophysiology, making it an imperative field of study.

MiR-1471 protects the aggravation of non-small-cell lung carcinoma by targeting FOXL1

This study detected the expression pattern of miR-1471 in non-small-cell lung cancer (NSCLC) tissues, and analyzed the prognostic significance of miR-1471 in NSCLC. Subsequently, potential targets of miR-1471 were screened for assessing the potential molecular mechanism in NSCLC. A total of 47 primary NSCLC cases treated by radical resection and systematic lymphadenectomy in the department of thoracic surgery were collected, as well as their clinical data. MiR-1471 levels in NSCLC tissues were detected by quantitative real-time polymerase chain reaction. The prognostic potential of miR-1471 in NSCLC was assessed by Kaplan-Meier method, followed by log-rank test. Potential target genes of miR-1471 and the binding sites were predicted by bioinformatics analysis, and screened for the optimal one. The binding relationship between miR-1471 and the target FOXL1 was examined by dual-luciferase reporter assay. Subsequently, biological functions of miR-1471 and FOXL1 in NSCLC cell functions were explored by cell counting kit-8 (CCK-8), 5-ethynyl-2'-deoxyuridine (EdU) assay and flow cytometry. MiR-1471 was downregulated in NSCLC tissues and its level was correlated to TNM staging in NSCLC patients. Overall survival was poor in NSCLC patients expressing low level of miR-1471. Overexpression of miR-1471 attenuated proliferative ability and arrested cell cycle progression in G1/S phase. FOXL1 was confirmed to be the target gene binding miR-1471. Its expression pattern and biological functions in NSCLC cells were contrary to those of miR-1471. MiR-1471 is downregulated in NSCLC samples, which is related to TNM staging and prognosis in NSCLC patients. Therefore, miR-1471 suppresses the malignant aggravation of NSCLC via inhibiting the translation of FOXL1 mRNA. In addition, it could be used as an effective biomarker for predicting the prognosis in NSCLC.

Up-Regulation of MiRNA-125a-5p Inhibits Cell Proliferation and Increases EGFR-TKI Induced Apoptosis in Lung Cancer Cells

BACKGROUND

Despite the dramatic efficacy of erlotinib, an EGFR tyrosine kinase inhibitor (TKI), most of non-small cell lung cancer (NSCLC) patients ultimately acquire resistance to this agent. Different studies indicated that miRNA-125a-5p is down-regulated in human lung cancer cells and may function as a tumor suppressor by targeting EGFR. However, the biological function of miRNA-125a-5p in NSCLC resistance to EGFR-TKIs is not fully understood. In this study the effect of miRNA-125a-5p on cell proliferation, apoptosis and sensitivity of the A549 lung cancer cells to erlotinib was investigated.

METHODS

After miRNA-125a-5p transfection, the expression levels of EGFR mRNA were measured by QRT-PCR. Trypan blue assays were performed to evaluate the proliferation of the A549 lung cancer cells. The cytotoxic effects of miRNA-125a-5p and erlotinib, alone and in combination, were determined using MTT assay. Combination index study was performed using the method of Chou-Talalay. Apoptosis was assessed using an ELISA cell death assay kit.

RESULTS

MiRNA-125a-5p clearly reduced the expression of EGFR mRNA in a time dependent manner, causing marked cell proliferation inhibition and spontaneous apoptosis (p<0.05, relative to control). Pretreatment with miRNA-125a-5p synergistically increased the cytotoxic effect of erlotinib and decreased its IC50. Furthermore, miRNA-125a-5p significantly enhanced the apoptotic effect of erlotinib. Negative control miRNA had no significant effect on biological parameter of the tumor cells.

CONCLUSIONS

Our data suggest that suppression of EGFR by miRNA-125a-5p can effectively trigger apoptosis and overcome EGFR-TKs resistance of lung cancer cells. Therefore, miRNA-125a-5p may be a potential therapeutic adjuvant in patients with lung cancer.
.

Targeting Epidermal Growth Factor Receptor by MiRNA-145 Inhibits Cell Growth and Sensitizes NSCLC Cells to Erlotinib

Background: Despite effective activity of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs), such as erlotinib, all non-small cell lung cancer (NSCLC) patients eventually acquire resistance to these agents. Studies have demonstrated that down-regulation of miRNA-145 leads to enhancement of EGFR expression, cell proliferation and metastasis. The aim of this study was to investigate the effect of miRNA-145 on sensitivity of the A549 NSCLC cells to erlotinib. Methods: Quantitative real-time PCR was used to examine the effect of miRNA-145 on EGFR expression. The effect of miRNA-145 on cell growth and sensitivity the lung cancer cells to erlotinib was examined by trypan blue and MTT assays, respectively. The combination index was calculated using the non-constant method of Chou-Talalay. Apoptosis was determined by ELISA cell death assay. Results: We found that miRNA-145 was markedly suppressed the expression of EGFR and inhibited the cancer cell growth, relative to blank control and negative control miRNA (p<0.05). Pretreatment with miRNA-145 synergistically enhanced the sensitivity of the lung cancer cells to erlotinib. Results of apoptosis assay revealed that miRNA-145 can induce apoptosis and increase the erlotinib-mediated apoptosis. Conclusions: Our data demonstrate that miRNA-145 play a critical role in the lung cancer cell growth, survival and EGFR-TKIs resistance possibly by regulation of EGFR. Therefore, miRNA-145 replacement therapy can become a new therapeutic strategy in lung cancer.

MicroRNA in Lung Cancer Metastasis

Tumor metastasis is a hallmark of cancer, with distant metastasis frequently developing in lung cancer, even at initial diagnosis, resulting in poor prognosis and high mortality. However, available biomarkers cannot reliably predict cancer spreading sites. The metastatic cascade involves highly complicated processes including invasion, migration, angiogenesis, and epithelial-to-mesenchymal transition that are tightly controlled by various genetic expression modalities along with interaction between cancer cells and the extracellular matrix. In particular, microRNAs (miRNAs), a group of small non-coding RNAs, can influence the transcriptional and post-transcriptional processes, with dysregulation of miRNA expression contributing to the regulation of cancer metastasis. Nevertheless, although miRNA-targeted therapy is widely studied in vitro and in vivo, this strategy currently affords limited feasibility and a few miRNA-targeted therapies for lung cancer have entered into clinical trials to date. Advances in understanding the molecular mechanism of metastasis will thus provide additional potential targets for lung cancer treatment. This review discusses the current research related to the role of miRNAs in lung cancer invasion and metastasis, with a particular focus on the different metastatic lesions and potential miRNA-targeted treatments for lung cancer with the expectation that further exploration of miRNA-targeted therapy may establish a new spectrum of lung cancer treatments.

Molecular predictors of brain metastasis-related microRNAs in lung adenocarcinoma

Brain metastasis (BM) is a major complication of lung adenocarcinoma (LAD). An investigation of the pathogenic mechanisms of BM, as well as the identification of appropriate molecular markers, is necessary. The aim of this study was to determine the expression patterns of microRNAs (miRNAs) in LAD with BM, and to investigate the biological role of these miRNAs during tumorigenesis. miRNA array profiles were used to identify BM-associated miRNAs. These miRNAs were independently validated in 155 LAD patients. Several in vivo and in vitro assays were performed to verify the effects of miRNAs on BM. We identified six miRNAs differentially expressed in patients with BM as compared to patients with BM. Of these, miR-4270 and miR-423-3p were further investigated. miR-4270 and miR-423-3p directly targeted MMP19 and P21, respectively, to influence cell viability, migration, and colony formation in vitro. miR-4270 downregulation and miR-423-3p upregulation was associated with an increased risk of BM in LAD patients. Thus, our results suggested that miR-4270 and miR-423-3p might play an important role in BM pathogenesis in LAD patients, and that these miRNAs might be useful prognostic and clinical treatment targets.

Identification of potential biomarkers of lung adenocarcinoma brain metastases via microarray analysis of cDNA expression profiles

Brain metastases originating from lung adenocarcinoma (LAD) occur frequently. The aim of the current study was to assess potential biomarkers for the prognosis of lung adenocarcinoma brain metastasis (LAD-BM) through the analysis of gene expression microarrays. The current study downloaded two gene expression datasets, GSE14108 and GSE10245, from the Gene Expression Omnibus database. From GSE14108 and GSE10245, 19 LAD-BM samples and 40 primary LAD samples were selected for analysis. To identify the differentially expressed genes (DEGs), the current study compared the two sample groups, using the limma R package. Subsequently, pathway enrichment analysis was conducted using the Cluster Profiler R package, and the construction of the protein-protein interaction (PPI) network was executed utilizing the Search Tool for the Retrieval of Interacting Genes database. The microRNA-target network was built using the TargetScore R package. Then, these networks were established and visualized using Cytoscape software. An array of 463 DEGs was identified in the LAD-BM samples, including 256 upregulated and 207 downregulated genes. Based on functional term enrichment analysis using the Gene Ontology database and signaling pathway enrichment analysis using the Kyoto Encyclopedia of Genes and Genomes database, it was identified that the overlapping DEGs were primarily involved in chemokine-associated signal transduction, which may mediate lung cancer cell metastasis to the brain. Chemokine ligand 2, lysozyme, matrix metalloproteinase-2 (MMP-2), lysyl oxidase (LOX) and granzyme B were identified as potential biomarkers according to a topological analysis of the PPI networks. Two notable nodes, MMP-2 and LOX, appeared in the PPI network and were key points in the microRNA-target network, as they were regulated by hsa-let-7d. Many DEGs and microRNAs were regarded as prognostic biomarkers for lung adenocarcinoma metastasis in the current study. These DEGs were primarily associated with chemokine-mediated signaling pathways. In addition, MMP-2 and LOX were predicted to be targets of hsa-let-7d.

MiR-423-5p in brain metastasis: potential role in diagnostics and molecular biology

During the last several years, a growing number of studies have shown that microRNAs (miRNAs) participate in cancer metastasis. Brain metastasis (BM) is a frequent complication of lung adenocarcinoma (LAD), and the incidence of locally advanced LAD with BM can be as high as 30-50%. This study was performed to identify the miRNA expression patterns of LAD with BM and to determine the biological role that miRNAs play in tumorigenesis. To this end, we conducted microarray and quantitative PCR analyses to evaluate BM-related miRNAs independently validated from a total of 155 patients with LAD. A series of in vivo and in vitro assays were also conducted to verify the impact of miRNAs on BM. We found significantly increased expression of miR-423-5p, and BM was predicted in non-small cell lung cancer when compared to LAD without BM. We next examined the function of miR-423-5p and discovered that it significantly promoted colony formation, cell motility, migration, and invasion in vitro. We computationally and experimentally confirmed that metastasis suppressor 1 (MTSS1) was a direct miR-423-5p target. Through a combination of image, histological, and molecular analyses, we found that miR-423-5p overexpression significantly increased tumor burden, local invasion, and distant BM. The level of MTSS1 expression was inversely correlated with miR-423-5p upregulation in the LAD specimens and was associated with survival of patients with BM. MiR-423-5p promoted BM in LAD and inhibited MTSS1 expression. Together, these results show that MiR-423-5p has the potential to be a marker of BM and/or a therapeutic target in LAD.

Potential Molecular Signatures Predictive of Lung Cancer Brain Metastasis

Brain metastases are the most common tumors of the central nervous system (CNS). Incidence rates vary according to primary tumor origin, whereas the majority of the cerebral metastases arise from primary tumors in the lung (40-50%). Brain metastases from lung cancer can occur concurrently or within months after lung cancer diagnosis. Survival rates after lung cancer brain metastasis diagnosis remain poor, to an utmost of 10 months. Therefore, prevention of brain metastasis is a critical concern in order to improve survival among cancer patients. Although several studies have been made in order to disclose the genetic and molecular mechanisms associated with CNS metastasis, the precise mechanisms that govern the CNS metastasis from lung cancer are yet to be clarified. The ability to forecast, which patients have a higher risk of brain metastasis occurrence, would aid cancer management approaches to diminish or prevent the development of brain metastasis and improve the clinical outcome for such patients. In this work, we revise genetic and molecular targets suitable for prediction of lung cancer CNS disease.

Machine Learning Based Prediction of Brain Metastasis of Patients with IIIA-N2 Lung Adenocarcinoma by a Three-miRNA Signature

OBJECTIVES: MicroRNAs (miRNAs) play a key role in governing posttranscriptional regulation through binding to the mRNAs of target genes. This study is to assess miRNAs expression profiles for identifying brain metastasis-related miRNAs to develop the predictive model by microarray in tumor tissues. METHODS: For this study, we screened the significant brain metastasis-related miRNAs from 77 lung adenocarcinoma (LUAD) patients with brain metastasis (BM+) or non-brain metastasis (BM−). A predictive model was developed from the training set (n = 42) using a random Forest supervised classification algorithm and a Class Centered Method, and then validated in a test set (n = 35) and further analysis in GSE62182 (n = 73). The independence of this signature in BM prediction was measured by multivariate logistic regression analysis. RESULTS: From the training set, the predictive model (including hsa-miR-210, hsa-miR-214 and hsa-miR-15a) stratified the patients into two groups with significantly different BM subtypes (90.4% of accuracy). The similar predictive power (91.4% of accuracy) was obtained in the test cohort. As an independent predictive factor, it was closely associated with BM and had high sensitivity and specificity in predicting BM in clinical practice. Moreover, functional enrichment analysis demonstrated that this signature involved in the signaling pathways positively correlated with cancer metastasis. CONCLUSION: These results suggested that the three-miRNA signature could develop a new random Forest model to predict the BM of LUAD patients. These findings emphasized the importance of miRNAs in diagnosing BM, and provided evidence for selecting treatment decisions and designing clinical trials.

Lung cancer-associated brain metastasis: Molecular mechanisms and therapeutic options

BACKGROUND

Lung cancer is the most common cause of cancer-related mortality in humans. There are several reasons for this high rate of mortality, including metastasis to several organs, especially the brain. In fact, lung cancer is responsible for approximately 50% of all brain metastases, which are very difficult to manage. Understanding the cellular and molecular mechanisms underlying lung cancer-associated brain metastasis brings up novel therapeutic promises with the hope to ameliorate the severity of the disease. Here, we provide an overview of the molecular mechanisms underlying the pathogenesis of lung cancer dissemination and metastasis to the brain, as well as promising horizons for impeding lung cancer brain metastasis, including the role of cancer stem cells, the blood-brain barrier, interactions of lung cancer cells with the brain microenvironment and lung cancer-driven systemic processes, as well as the role of growth factor/receptor tyrosine kinases, cell adhesion molecules and non-coding RNAs. In addition, we provide an overview of current and novel therapeutic approaches, including radiotherapy, surgery and stereotactic radiosurgery, chemotherapy, as also targeted cancer stem cell and epithelial-mesenchymal transition (EMT)-based therapies, micro-RNA-based therapies and other small molecule or antibody-based therapies. We will also discuss the daunting potential of some combined therapies.

CONCLUSIONS

The identification of molecular mechanisms underlying lung cancer metastasis has opened up new avenues towards their eradication and provides interesting opportunities for future research aimed at the development of novel targeted therapies.

[Tumor Cells and Micro-environment in Brain Metastases]

近年来，随着早期诊断的方法的出现及精准治疗的应用，肺癌患者的生存及生活质量都得到很大改善。然而，对于肺癌的脑转移病灶，目前仍缺乏一个理想的治疗方案，严重影响了该部分患者生存状态。了解肿瘤细胞如何在中枢神经系统定植、生长和侵袭等相关生物学行为及其产生机制对预防及治疗肿瘤细胞脑转移病灶具有重大的意义。“种子-土壤”这一假说可以很好的解释这一过程，这一假说的关键即肿瘤细胞可与中枢神经系统微环境各组成之间产生相互适应性变化，正是这种相互作用决定了脑转移病灶的发生发展。本文就脑转移肿瘤细胞、脑转移肿瘤微环境及他们之间的相互作用进行综述，旨在为脑转移病灶的治疗提供新的思路。

miR-297 acts as an oncogene by targeting GPC5 in lung adenocarcinoma

OBJECTIVES

Emerging studies have demonstrated that microRNAs (miRNAs) play crucial roles in carcinogenesis of many developing human tumours. However, the functions and mechanisms of miR-297 in lung cancer have, up to now, been largely undefined.

MATERIALS AND METHODS

Here, miR-297 expression was measured in lung adenocarcinoma tissues and cell lines, using qRT-PCR. Lung adenocarcinoma cell line was treated with an miR-297 mimic. MTT and colony analysis were performed to detect cell proliferation and colony formation. The direct target gene of miR-297 was assessed by qRT-PCR, Western blotting and luciferase assays.

RESULTS

We demonstrated that miR-297 expression was upregulated in lung adenocarcinomas compared to adjacent normal tissues. Expression of miR-297 was also upregulated in tested lung adenocarcinoma cell lines. Ectopic expression of miR-297 enhanced lung adenocarcinoma cell proliferation and colony formation. Furthermore, overexpression of miR-297 promoted cell migration and invasion. In addition, we identified Glypican-5 (GPC5) as a direct target gene of miR-297 in lung adenocarcinoma cells. Expression of GPC5 was downregulated in both lung adenocarcinoma tissues and cell lines. Moreover, expression of GPC5 was inversely associated with expression of miR-297 in lung adenocarcinoma tissues.

CONCLUSIONS

These results suggest that miR-297 acted as an oncogenic miRNA, partly by targeting GPC5, adenocarcinoma of the lung.

MicroRNAs in non-small cell lung cancer and idiopathic pulmonary fibrosis

In spite of advances in the diagnosis and current molecular target therapies of lung cancer, this disease remains the most common cause of cancer-related death worldwide. Approximately 80% of lung cancers is non-small cell lung cancer (NSCLC), and 5-year survival rate of the disease is ~20%. On the other hand, idiopathic pulmonary fibrosis (IPF) is a chronic, progressive interstitial lung disease of unknown etiology. IPF is refractory to treatment and has a very low survival rate. Moreover, IPF is frequently associated with lung cancer. However, the common mechanisms shared by these two diseases remain poorly understood. In the post-genome sequence era, the discovery of noncoding RNAs, particularly microRNAs (miRNAs), has had a major impact on most biomedical fields, and these small molecules have been shown to contribute to the pathogenesis of NSCLC and IPF. Investigation of novel RNA networks mediated by miRNAs has improved our understanding of the molecular mechanisms of these diseases. This review summarizes our current knowledge on aberrantly expressed miRNAs regulating NSCLC and IPF based on miRNA expression signatures.

MicroRNA Expression Profile on Solid Subtype of Invasive Lung Adenocarcinoma Reveals a Panel of Four miRNAs to Be Associated with Poor Prognosis in Chinese Patients

According to the reclassification of lung adenocarcinoma (LAC) proposed in 2011, solid predominant lung adenocarcinoma (SPA) has been associated with poor outcomes for LAC patients. However, the prognostic value of the presence of solid subtype remains unclear. Besides, there is little data about the roles of microRNA (miRNA) in solid subtype of LAC. In this study, 243 LAC patients were classified into solid subtype positive and negative groups (S+ LAC, n=134 and S- LAC, n=109) according to whether the solid subtype was more than 5% of the tumor component or not. We analyzed the relationship between solid subtype and patients' outcome by univariate and multivariate analyses. Solid subtype was proved to be significantly associated with the 5-year overall survival and played as an independent prognostic factor for stage I-III invasive LAC patients. Then miRNA microarray was used to identify differentially expressed miRNAs in solid subtype, resulting in 31 differential miRNAs. Quantitative reverse transcription-PCR (QRT-PCR) was used to validate 4 key miRNAs (miR-133b, miR-155-5p, miR-124-3p, miR-145-5p). Further, CCK-8 and transwell assays were performed to validate the impact of one dysregulated miRNA (miR-133b) on LAC cell function. Interestingly, while miR-133b could significantly inhibit the proliferation of A549 and SPC-A1, it showed no effect on the migration or invasion of LAC cell lines. These results suggest that solid subtype can exert independent prognostic impact on LAC patients, and 4 important dysregulated miRNAs in solid subtype of LAC may be involved in the malignancy of S+LAC, thus may further have clinical perspective for S+ LAC in the future.

The role of microRNA in metastatic processes of non-small cell lung carcinoma

BACKGROUND

MicroRNAs are small non-coding one-stranded RNA molecules that play an important role in the post-transcriptional regulation of genes. Bioinformatic predictions indicate that each miRNA can regulate hundreds of target genes. MicroRNA expression can be associated with various cellular processes leading to the metastasis of malignant tumours including non-small cell lung carcinoma. This review summarizes current knowledge on the role of microRNAs in NSCLC metastasis to the brain and lymph nodes.

METHODS

A search of the NCBI/PubMed database for publications on expression levels and the mechanisms of microRNA action in NSCLC metastasis.

RESULTS AND CONCLUSION

Dysregulation of microRNAs in NSCLC can be associated with brain and lymph node metastasis. There are differences in microRNA expression profiling between NSCLC with and without metastases but it is currently not possible to reliably predict the site of metastasis in NSCLC. Based on data from RNAmicroarrays, bioinformatics analysis is able to predict the target genes of highlighted microRNAs, providing us with complex information about cancer cell features such as enhanced proliferation, migration and invasion. Such microRNAs may then be knocked-down using siRNAs or substituted with miRNA mimics. RNA microarray profiling may thus be a useful tool to select up- or down-regulated microRNAs. A number of authors suggest that microRNAs could serve as biomarkers and therapeutic targets in the treatment of NSCLC metastasis.

Non-coding RNAs in cancer brain metastasis

More than 90% of cancer death is attributed to metastatic disease, and the brain is one of the major metastatic sites of melanoma, colon, renal, lung and breast cancers. Despite the recent advancement of targeted therapy for cancer, the incidence of brain metastasis is increasing. One reason is that most therapeutic drugs can't penetrate blood-brain-barrier and tumor cells find the brain as sanctuary site. In this review, we describe the pathophysiology of brain metastases to introduce the latest understandings of metastatic brain malignancies. This review also particularly focuses on non-coding RNAs and their roles in cancer brain metastasis. Furthermore, we discuss the roles of the extracellular vesicles as they are known to transport information between cells to initiate cancer cell-microenvironment communication. The potential clinical translation of non-coding RNAs as a tool for diagnosis and for treatment is also discussed in this review. At the end, the computational aspects of non-coding RNA detection, the sequence and structure calculation and epigenetic regulation of non-coding RNA in brain metastasis are discussed.

miR-873 induces lung adenocarcinoma cell proliferation and migration by targeting SRCIN1

microRNAs (miRNAs) are endogenously expressed, conserved and small noncoding RNA that regulate gene expression by the post-transcriptional level. In this study, we aim to examine the role of miR-873 in lung adenocarcinoma. We found that the expression of miR-873 was upregulated in four lung adenocarcinoma cell lines and tissues. In addition, the expression levels of SRCIN1 were inversely correlated with the expression levels of miR-873 in lung adenocarcinoma tissues. Furthermore, SRCIN1 was confirmed asthe direct target of miR-873 by luciferase reporter assay and Western blotting. Overexpression of miR-873 promoted the proliferation and migration of lung adenocarcinoma cells, while SRCIN1 upregulation inhibited their proliferation and migration. Restoration of SRCIN1 could significantly reverse the proliferation and migration promotion imposed by miR-873. In summary, this study reveals for the first time that miR-873 increase the lung adenocarcinoma cell proliferation and migration through directly inhibiting SRCIN1 expression.

Acquirement of DNA copy number variations in non-small cell lung cancer metastasis to the brain

Brain metastasis is a major complication of non-small cell lung cancer (NSCLC) and leads to most of the mortality of this disease. However, the biological mechanisms and molecular features in brain metastasis of NSCLC are poorly understood. In the present study, we compared whole-genome copy number variations (CNVs) between a primary lung adenocarcinoma and secondary metastatic brain lesion from the same patient using array comparative genomic hybridization (aCGH). The number of CNV regions was markedly higher in the secondary metastatic tumor than the primary tumor in the lung. In detail, the common CNVs in both tumors included gains of 7p22, 7p12-p11, 7q11, 7q22, 21q22, and 19q13; gains of 1p33-p34, 1q22, 5p13 and 14q11 whereas losses of 3p, 4q31, 5q, 11p15, Xp21-p22 and Xq21 were identified only in the secondary lesion. Gene Ontology enrichment analysis revealed that the genes with amplified copy numbers in both tumors were related to such processes as DNA replication and mismatch repair. Genes only amplified in the metastatic tumor were enriched in processes that include leukocyte migration and organ development, and genes with a lower copy number in the secondary tumor included the processes of proteolysis regulation, negative regulation of cell proliferation and cell adhesion. These findings provided new insight into the genomic mechanism of the spread of lung adenocarcinoma to the brain, and the candidate genes identified serve as novel indicators or putative targets in NSCLC brain metastasis.

Low miR-145 expression level is associated with poor pathological differentiation and poor prognosis in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is the first cause of cancer related death in the world. Biomarkers to predict the relapse and drug resistance could be extremely useful for a clinical doctor to monitor high risk patients and select rational regimen. miRNAs play an important role in lung cancer and detection samples are relatively easy to be obtained, miRNAs could become a promising means of comprehending the oncogenesis and pathogenesis of lung cancer. This study aimed to investigate the function of miR-145 to work as a biomarker in NSCLC. miR-145 expression level in 48 NSCLC tumor tissues and their matched normal tissues were detected by qRT-PCR. miR-145 in 18 paraffin-embedded samples underwent chemotherapy and were assessed by in situ hybridization (ISH). Here we show that miR-145 was down-regulated in NSCLC tissues; down-regulation of miR-145 was correlated with late clinical stage and poorly differentiated carcinoma, and, low expression level of miR-145 could also predict chemotherapy resistance and shorter disease-free survival (DFS). These findings indicated that miR-145 expression may be a useful prognostic marker that could be used for predicting poor differentiation, chemo-resistance and shore DFS.

miR-214 as a key hub that controls cancer networks: small player, multiple functions

MicroRNAs are short regulatory RNAs that are able to post-transcriptionally modulate gene expression and that have crucial roles in the control of physiological and pathological processes including cancer onset, growth, and progression. miR-214, located inside the sequence of the long noncoding Dmn3os transcript, contributes to the regulation of normal and cancer cell biology, even if it operates in a context-dependent and sometimes contradictory manner. miR-214 is deregulated in several human tumors including melanoma, breast, ovarian, gastric, and hepatocellular carcinomas. miR-214's pleiotropic and tumor-specific contribution to various cancer formation and progression hallmarks is achieved via its several target genes. In fact, miR-214 behaves as a key hub by coordinating fundamental signaling networks such as PTEN/AKT, β-catenin, and tyrosine kinase receptor pathways. Interestingly, miR-214 also regulates the levels of crucial gene expression modulators: the epigenetic repressor Ezh2, "genome guardian" p53, transcription factors TFAP2, and another microRNA, miR-148b. Thus, miR-214 seems to have essential roles in coordinating tumor proliferation, stemness, angiogenesis, invasiveness, extravasation, metastasis, resistance to chemotherapy, and microenvironment. The sum of current literature reports suggests that miR-214 is a molecular hub involved in the control of cancer networks and, as such, could be a potential diagnostic/prognostic biomarker and target for therapeutic intervention.

MiR-145 acts as a metastasis suppressor by targeting metadherin in lung cancer

MiR-145 has been reported to be downregulated in multiple tumors. It acts as a tumor suppressor in lung cancer. In this study, we investigated the potential effects of miR-145 on invasion and metastasis and the molecular mechanism in non-small cell lung cancer. MiR-145 was downregulated in the NSCLC specimens and significantly correlated with advanced clinical stage and lymph node metastasis. In addition, AEG-1/MTDH was a direct target of miR-145, and the expression of AEG-1/MTDH was inversely correlated with miR-145 expression in NSCLC tissues. Ectopic expression of miR-145 suppressed cell invasion and metastasis in NSCLC cells. AEG-1/MTDH overexpression partially reversed the suppressive effect of miR-145. These findings provide novel insights with potential therapeutic applications for the treatment of NSCLC.

Non-coding RNAs in lung cancer

The discovery that protein-coding genes represent less than 2% of all human genome, and the evidence that more than 90% of it is actively transcribed, changed the classical point of view of the central dogma of molecular biology, which was always based on the assumption that RNA functions mainly as an intermediate bridge between DNA sequences and protein synthesis machinery. Accumulating data indicates that non-coding RNAs are involved in different physiological processes, providing for the maintenance of cellular homeostasis. They are important regulators of gene expression, cellular differentiation, proliferation, migration, apoptosis, and stem cell maintenance. Alterations and disruptions of their expression or activity have increasingly been associated with pathological changes of cancer cells, this evidence and the prospect of using these molecules as diagnostic markers and therapeutic targets, make currently non-coding RNAs among the most relevant molecules in cancer research. In this paper we will provide an overview of non-coding RNA function and disruption in lung cancer biology, also focusing on their potential as diagnostic, prognostic and predictive biomarkers.

MicroRNA-145 inhibits cell proliferation by directly targeting ADAM17 in hepatocellular carcinoma

MicroRNAs (miRNAs) are key regulators in cell processes. Emerging evidence has suggested that there is a direct association between miRNAs and cancer. However, the exact regulatory mechanisms of miRNAs in tumorigenesis are poorly understood. In the present study, we showed that miR-145 is able to significantly reduce mRNA and protein expression levels of A disintegrin and metalloproteinase 17 (ADAM17) in liver cancer cells (SMMC-7721, BEL-7402 and Huh-7). Dual luciferase reporter assays confirmed that ADAM17 is a direct target of miR-145. Notably, we found that miR-145 inhibits cell proliferation and growth activity in SMMC-7721 cells. These results demonstrated that it may be exert the function of tumor suppression in a particular link of cancer cell growth. Further studies revealed that the silencing of ADAM17 decreased the proliferation and growth activity of SMMC-7721 cells. Moreover, it reduced the expression of MMP-9. In conclusion, miR-145 inhibits liver cancer cell proliferation by directly targeting ADAM17. Thus, it may become a promising biological target in the treatment strategy of hepatocellular carcinoma.

MicroRNAs in brain metastases: potential role as diagnostics and therapeutics

Brain metastases remain a daunting adversary that negatively impact patient survival. Metastatic brain tumors affect up to 45% of all cancer patients with systemic cancer and account for ~20% of all cancer-related deaths. A complex network of non-coding RNA molecules, microRNAs (miRNAs), regulate tumor metastasis. The brain micro-environment modulates metastatic tumor growth; however, defining the precise genetic events that promote metastasis in the brain niche represents an important, unresolved problem. Understanding these events will reveal disease-based targets and offer effective strategies to treat brain metastases. Effective therapeutic strategies based upon the biology of brain metastases represent an urgent, unmet need with immediate potential for clinical impact. Studies have demonstrated the ability of miRNAs to distinguish normal from cancerous cells, primary from secondary brain tumors, and correctly categorize metastatic brain tumor tissue of origin based solely on miRNA profiles. Interestingly, manipulation of miRNAs has proven effective in cancer treatment. With the promise of reduced toxicity, increased efficacy and individually directed personalized anti-cancer therapy, using miRNA in the treatment of metastatic brain tumors may prove very useful and improve patient outcome. In this review, we focus on the potential of miRNAs as diagnostic and therapeutic targets for the treatment of metastatic brain lesions.

Brain metastasis: new opportunities to tackle therapeutic resistance

Brain metastasis is a devastating complication of cancer with unmet therapeutic needs. The incidence of brain metastasis has been rising in cancer patients and its response to treatment is limited due to the singular characteristics of brain metastasis (i.e., blood-brain-barrier, immune system, stroma). Despite improvements in the treatment and control of extracranial disease, the outcomes of patients with brain metastasis remain dismal. The mechanisms that allow tumor cells to promulgate metastases to the brain remain poorly understood. Further work is required to identify the molecular alterations inherent to brain metastasis in order to identify novel therapeutic targets and explicate the mechanisms of resistance to systemic therapeutics. In this article, we review current knowledge of the unique characteristics of brain metastasis, implications in therapeutic resistance, and the possibility of developing biomarkers to rationally guide the use of targeted agents.