MiR-155 inhibits the sensitivity of lung cancer cells to cisplatin via negative regulation of Apaf-1 expression

New Concepts in Cancer Biomarkers: Circulating miRNAs in Liquid Biopsies

The effective and efficient management of cancer patients relies upon early diagnosis and/or the monitoring of treatment, something that is often difficult to achieve using standard tissue biopsy techniques. Biological fluids such as blood hold great possibilities as a source of non-invasive cancer biomarkers that can act as surrogate markers to biopsy-based sampling. The non-invasive nature of these “liquid biopsies” ultimately means that cancer detection may be earlier and that the ability to monitor disease progression and/or treatment response represents a paradigm shift in the treatment of cancer patients. Below, we review one of the most promising classes of circulating cancer biomarkers: microRNAs (miRNAs). In particular, we will consider their history, the controversy surrounding their origin and biology, and, most importantly, the hurdles that remain to be overcome if they are really to become part of future clinical practice.

MicroRNA-155 expression is independently predictive of outcome in chordoma

Background

Chordoma pathogenesis remains poorly understood. In this study, we aimed to evaluate the relationships between microRNA-155 (miR-155) expression and the clinicopathological features of chordoma patients, and to evaluate the functional role of miR-155 in chordoma.

Methods

The miRNA expression profiles were analyzed using miRNA microarray assays. Regulatory activity of miR-155 was assessed using bioinformatic tools. miR-155 expression levels were validated by reverse transcription-polymerase chain reaction. The relationships between miR-155 expression and the clinicopathological features of chordoma patients were analyzed. Proliferative, migratory and invasive activities were assessed by MTT, wound healing, and Matrigel invasion assays, respectively.

Results

The miRNA microarray assay revealed miR-155 to be highly expressed and biologically active in chordoma. miR-155 expression in chordoma tissues was significantly elevated, and this expression correlated significantly with disease stage (p = 0.036) and the presence of metastasis (p = 0.035). miR-155 expression also correlated significantly with poor outcomes for chordoma patients (hazard ratio, 5.32; p = 0.045). Inhibition of miR-155 expression suppressed proliferation, and the migratory and invasive activities of chordoma cells.

Conclusions

We have shown miR-155 expression to independently affect prognosis in chordoma. These results collectively indicate that miR-155 expression may serve not only as a prognostic marker, but also as a potential therapeutic target in chordoma.

MicroRNA-155 promotes apoptosis in SKOV3, A2780, and primary cultured ovarian cancer cells

MicroRNAs (miRNAs) are a large group of small non-coding RNAs that can negatively regulate gene expression at the post-transcriptional level. The deregulation of miRNAs has been associated with tumorigenesis, drug resistance, and prognosis in cancers. Deregulated miR-155 has been reported in numerous cancers; however, its function remains unclear. 4',6-Diamidino-2-phenylindole (DAPI) staining and terminal-deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) techniques were used to determine the effects of a miR-155 mimic or inhibitor on the apoptotic ratio of ovarian cancer cells induced by cisplatin. Bioinformatic predictions, the dual-luciferase reporter assay, and western blot analysis were used to detect how miR-155 regulates X-linked inhibitor of apoptosis protein (XIAP). We demonstrated that a miR-155 mimic could decrease the IC50 value of cisplatin in SKOV3 ovarian cancer cells. Subsequently, gain- and loss-of-function analyses with a miR-155 mimic and inhibitor showed that miR-155 sensitizes ovarian cancer cells to cisplatin. Furthermore, the results from the luciferase assays and western blot analysis identified XIAP as the direct target of miR-155. In addition, introducing XIAP cDNA without a three prime untranslated region (3'-UTR) rescued the miR-155 promotion of apoptosis. These results indicate that miR-155 mediates cisplatin-induced apoptosis by targeting XIAP in ovarian cancer cells and that miR-155 could be a potential therapeutic target to increase the efficiency of ovarian cancer interventions.

Does miRNA-155 Promote Cyclooxygenase-2 Expression in Cancer?

Preclinical Research MicroRNA (miR)-155 and cyclooxygenase (COX)-2 are both elevated in numerous cancers including colorectal cancer. MiR-155 enhances COX-2 expression and is an established regulator of epithelial-mesenchymal transition and inflammation. Inhibition of miR-155 or COX-2 exhibit similar negative effects on tumorigenicity. Thus, it is hypothesized that miR-155 may be a promising target for antagonizing COX-2 expression in colorectal and other cancers.

The Emerging Role of miRNAs in HTLV-1 Infection and ATLL Pathogenesis

Human T-cell leukemia virus (HTLV)-1 is a human retrovirus and the etiological agent of adult T-cell leukemia/lymphoma (ATLL), a fatal malignancy of CD4/CD25+ T lymphocytes. In recent years, cellular as well as virus-encoded microRNA (miRNA) have been shown to deregulate signaling pathways to favor virus life cycle. HTLV-1 does not encode miRNA, but several studies have demonstrated that cellular miRNA expression is affected in infected cells. Distinct mechanisms such as transcriptional, epigenetic or interference with miRNA processing machinery have been involved. This article reviews the current knowledge of the role of cellular microRNAs in virus infection, replication, immune escape and pathogenesis of HTLV-1.

Upregulation of microRNA-23a regulates proliferation and apoptosis by targeting APAF-1 in laryngeal carcinoma

MicroRNA-23a (miR-23a) is a potential biomarker for laryngeal cancer. Apoptotic protease activating factor 1 (APAF-1) was recently demonstrated to be a target of miR-23a. However, whether miR-23a exerts its effects via APAF-1 in laryngeal cancer, remains unknown. In the present study, miR-23a expression was detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). APAF-1 mRNA and protein expression levels were assayed by RT-qPCR and western blotting, respectively. Binding of miR-23a to APAF-1 was monitored by a luciferase reporter assay. Gain-of-function and loss-of-function studies were performed in order to investigate the roles of miR-23a and APAF-1 in Hep2 cell proliferation and apoptosis. miR-23a and APAF-1 were found to be significantly upregulated and downregulated, respectively, in laryngeal cancer tissues, and there was a significant negative correlation between APAF-1 and miR-23a expression. The results of the luciferase reporter assay demonstrated that miR-23a bound directly to the APAF-1 mRNA 3'-untranslated region. Ectopic expression of miR-23a and knockdown of APAF-1 significantly promoted cell proliferation and colony formation, and inhibited early apoptosis in Hep2 cells. In conclusion, miR-23a acts as an oncogenic regulator in laryngeal carcinoma by directly targeting APAF-1, and may be a useful biomarker in the diagnosis and treatment of laryngeal carcinoma.

Recent advances of microRNA-based molecular diagnostics to reduce false-positive lung cancer imaging

Lung cancer is the leading cause of cancer deaths in the world. Advances in early detection crucial to enable timely curative surgery have been made in recent years. Cost-benefit profiles of lung cancer screening in smokers by low-dose computed tomography are still under evaluation. In particular, the high false-positive rates of low-dose computed tomography, together with the issue of overdiagnosis and the overall costs of screening, prompted a focus on the development of noninvasive complementary biomarkers to implement lung cancer screening. MicroRNA are a new class of blood-based biomarkers useful for early lung cancer detection and prognosis definition. Here, we discuss the seminal publications that reported circulating microRNA signatures with the greatest potential to impact clinical activity and patient care.

MicroRNA-221 accelerates the proliferation of laryngeal cancer cell line Hep-2 by suppressing Apaf-1

Laryngeal cancer is one of the most commonly occurring malignant cancers of the head and neck region. In the present study, we investigated the roles of miR-221 in laryngeal squamous cell carcinoma cell line, Hep-2. We examined the function and mechanism of miR-221 in Hep-2 cells using techniques of cell biology and molecular pathology, such as western blotting, quantitative PCR, immunohistochemical staining and flow cytometry. Using a luciferase assay, the apoptotic protease activating factor-1 (Apaf-1) mRNA 3'-UTR was shown to have complementary binding sites using bioinformatics prediction software including TargetScan, PicTar and miRanda. In conclusion, our results showed that miR-221 inhibition caused elevated expression levels of the Apaf-1 apoptotic pathway proteins caspase-3, -8 and -9. miR-221 may therefore be used as a novel therapeutic target for laryngeal cancer.

microRNA and Lung Cancer

Lung cancer is the leading cause of cancer mortality worldwide. microRNAs (miRNAs) have been established as players with a relevant role in lung cancer development, epithelial-mesenchymal transition and response to therapy. Additionally, in the last decade, miRNAs, measured in resected tumor samples or in fine-needle aspirate samples have emerged as compelling biomarkers for tumor diagnosis, prognosis, and prediction of response to treatment, due to the ease of their detection and in their extreme specificity. Moreover, miRNAs present in sputum, in plasma, in serum or in whole-blood have increasingly been explored in the last 5 years as less invasive biomarkers for the early detection of cancers.

Aroclor 1254 inhibits cell viability and induces apoptosis of human A549 lung cancer cells by modulating the intracellular Ca(2+) level and ROS production through the mitochondrial pathway

To study the acute toxic effects of PCBs on airway exposure, the cell viability, apoptosis and mitochondrial functions of human lung cancer cell line A549 were measured and compared after Aroclor 1254 exposure for different time. The results showed that Aroclor 1254 could inhibit cell viability and increase cell apoptosis in a concentration- and time-dependent manner. The mitochondrial apoptosis pathway was confirmed playing an important role. ROS elevation was an early response within 1h treatment of Aroclor 1254. Then after 4 h of Aroclor 1254 exposure, the intracellular calcium level increased and mitochondrial transmembrane potential (ΔΨm) collapsed, accompanying with Cytochrome c (Cyt-c) leakage, boosting expression of Bax, Apaf-1 and miRNA155, which were involved in the mitochondrial apoptosis pathway. After 24 h of Aroclor 1254 exposure, ROS returned to normal level, but cell apoptosis rate was higher than that at 4 h with ΔΨm continued collapsing and intracellular calcium increased. In conclusion, Aroclor 1254 could suppress cell viability and induce apoptosis in A549 cells, which was associated with ROS over-production and elevated cellular Ca(2+) level, which may result in mitochondrial dysfunction, inducing expression of Bax/Cyt-c/Apaf-1 and miRNA155.

Epigenetics of lung cancer

Lung cancer is the leading cause of cancer-related mortality in the United States. Epigenetic alterations, including DNA methylation, histone modifications, and noncoding RNA expression, have been reported widely in the literature to play a major role in the genesis of lung cancer. The goal of this review is to summarize the common epigenetic changes associated with lung cancer to give some clarity to its etiology, and to provide an overview of the potential translational applications of these changes, including applications for early detection, diagnosis, prognostication, and therapeutics.

Combination of microRNA therapeutics with small-molecule anticancer drugs: mechanism of action and co-delivery nanocarriers

MicroRNAs (miRNAs) regulate multiple molecular pathways vital for the hallmarks of cancer with a high degree of biochemical specificity and potency. By restoring tumor suppressive miRNAs or ablating oncomiRs, miRNA-based therapies can sensitize cancer cells to conventional cytotoxins and the molecularly targeted drugs by promoting apoptosis and autophagy, reverting epithelial-to-mesenchymal transition, suppressing tumor angiogenesis, and downregulating efflux transporters. The development of miRNA-based therapeutics in combination with small-molecule anticancer drugs provides an unprecedented opportunity to counteract chemoresistance and improve treatment outcome in a broad range of human cancers. This review summarizes the mechanisms and advantages for the combination therapies involving miRNAs and small-molecule drugs, as well as the recent advances in the co-delivery nanocarriers for these agents.

The emerging role of microRNAs in resistance to lung cancer treatments

One of the major challenges in the treatment of lung cancer is the development of drug resistance. This represents a major obstacle in the treatment of patients, limiting the efficacy of both conventional chemotherapy and biological therapies. Deciphering the mechanisms of resistance is critical to further understanding the multifactorial pathways involved, and in developing more specific targeted treatments. To date, numerous studies have reported the potential role of microRNAs (miRNAs) in resistance to various cancer treatments. MicroRNAs are a family of small non-coding RNAs that regulate gene expression by sequence-specific targeting of mRNAs causing translational repression or mRNA degradation. More than 1200 validated human miRNAs have been identified to date. While as little as one miRNA can regulate hundreds of targets, a single target can also be affected by multiple miRNAs. Evidence suggests that dysregulation of specific miRNAs may be involved in the acquisition of resistance to a number of cancer treatments, thereby modulating the sensitivity of cancer cells to such therapies. Therefore, targeting miRNAs may be an attractive strategy for developing novel and more effective individualized therapies, improving drug efficiency, and for predicting patient response to different treatments. In this review, we provide an overview on the role of miRNAs in resistance to current lung cancer therapies and novel biological agents.

Seed targeting with tiny anti-miR-155 inhibits malignant progression of multiple myeloma cells

BACKGROUND

miR-155 acts as a ubiquitous oncogene in major classes of human cancers and is a potential target for therapeutic intervention. However, the role of miR-155 in multiple myeloma is poorly understood.

METHODS

To explore the role of miR-155 in multiple myeloma, we assessed the influence of tiny seed-targeting anti-miR-155 (t-anti-miR-155) on multiple myeloma cell line (RPMI-8266) viability and apoptosis in vitro.

RESULTS

t-anti-miR-155 significantly inhibited multiple myeloma cell proliferation, migration, and colony formation. Additionally, t-anti-miR-155 significantly increased CD19 positive cell numbers, which are novel biomarkers for multiple myeloma and suppressor of cytokine signaling 1(SOCS1) was shown to be a target gene for miR-155 in multiple myeloma. Finally, the miR-155 signaling pathway was investigated by KEGG assay.

CONCLUSION

miR-155 in RPMI-8266 cells is a critical oncomiR in multiple myeloma and seed-targeting t-anti-miR-155 might be a novel strategy for miR-155-based therapeutics.

MicroRNA-155 deficient mice experience heightened kidney toxicity when dosed with cisplatin

The development of nephrotoxicity limits the maximum achievable dosage and treatment intervals for cisplatin chemotherapy. Therefore, identifying mechanisms that regulate this toxicity could offer novel methods to optimize cisplatin delivery. MicroRNAs are capable of regulating many different genes, and can influence diverse cellular processes, including cell death and apoptosis. We previously observed miR-155 to be highly increased following ischemic or toxic injury to the kidneys and, therefore, sought to determine whether mice deficient in miR-155 would respond differently to kidney injury. We treated C57BL/6 and miR-155(-/-) mice with 20 mg/kg of cisplatin and found a significantly higher level of kidney injury in the miR-155(-/-) mice. Genome-wide expression profiling and bioinformatic analysis indicated the activation of a number of canonical signaling pathways relating to apoptosis and oxidative stress over the course of the injury, and identified potential upstream regulators of these effects. One predicted upstream regulator was c-Fos, which has two confirmed miR-155 binding sites in its 3' UTR and, therefore, can be directly regulated by miR-155. We established that the miR-155(-/-) mice had significantly higher levels of c-Fos mRNA and protein than the C57BL/6 mice at 72 h after cisplatin exposure. These data indicate a role for miR-155 in the cisplatin response and suggest that targeting of c-Fos could be investigated to reduce cisplatin-induced nephrotoxicity.

microRNAs in cancer cell response to ionizing radiation

SIGNIFICANCE

microRNAs (miRNA) have been characterized as master regulators of the genome. As such, miRNAs are responsible for regulating almost every cellular pathway, including the DNA damage response (DDR) after ionizing radiation (IR). IR is a therapeutic tool that is used for the treatment of several types of cancer, yet the mechanism behind radiation response is not fully understood.

RECENT ADVANCES

It has been demonstrated that IR can alter miRNA expression profiles, varying greatly from one cell type to the next. It is possible that this variation contributes to the range of tumor cell responsiveness that is observed after radiotherapy, especially considering the extensive role for miRNAs in regulating the DDR. In addition, individual miRNAs or miRNA families have been shown to play a multifaceted role in the DDR, regulating multiple members in a single pathway.

CRITICAL ISSUES

In this review, we will discuss the effects of radiation on miRNA expression as well as explore the function of miRNAs in regulating the cellular response to radiation-induced damage. We will discuss the importance of miRNA regulation at each stage of the DDR, including signal transduction, DNA damage sensing, cell cycle checkpoint activation, DNA double-strand break repair, and apoptosis. We will focus on emphasizing the importance of a single miRNA targeting several mediators within a pathway.

FUTURE DIRECTIONS

miRNAs will continue to emerge as critical regulators of the DDR. Understanding the role of miRNAs in the response to IR will provide insights for improving the current standard therapy.

MicroRNAs in lung cancer

MicroRNAs have become recognized as key players in the development of cancer. They are a family of small non-coding RNAs that can negatively regulate the expression of cancer-related genes by sequence-selective targeting of mRNAs, leading to either mRNA degradation or translational repression. Lung cancer is the leading cause of cancer-related death worldwide with a substantially low survival rate. MicroRNAs have been confirmed to play roles in lung cancer development, epithelial-mesenchymal transition and response to therapy. They are also being studied for their future use as diagnostic and prognostic biomarkers and as potential therapeutic targets. In this review we focus on the role of dysregulated microRNA expression in lung tumorigenesis. We also discuss the role of microRNAs in therapeutic resistance and as biomarkers. We further look into the progress made and challenges remaining in using microRNAs for therapy in lung cancer.

Systems biology approaches to develop innovative strategies for lung cancer therapy

Lung cancer (LC) is a number one killer of cancer-related death among men and women worldwide. Major advances have been made in the diagnosis, staging and use of surgery for LC, but systemic chemotherapy and radiotherapy alone or in combination with some targeted agents remains the core treatment of advanced LC. Unfortunately, in spite of improved diagnosis, surgical methods and new treatments, mortality is still extremely high among LC patients. To understand the precise functioning of signaling pathways associated with resistance to current treatments in LC, as well as to identify novel treatment regimens, a holistic approach to analyze signaling networks should be applied. Here, we describe systems biology-based approaches to generate biomarkers and novel therapeutic targets in LC, as well as how this may contribute to personalized treatment for this malignancy.

The pivotal role of microRNA-155 in the control of cancer

microRNAs (miRNAs) are emerging as important gene expression regulators linked to various biological processes at a posttranscriptional level. miRNAs have been known to play important roles in cell proliferation, cell differentiation, and apoptosis. Recently, accumulate studies indicate that up-regulation of miR-155 has been described in several types of human tumors. miR-155 has been considered to act as an oncogene or a tumor suppressor, depending on tumor system. Silencing oncomiRs or gene therapy approaches could be an effective therapeutic approach against tumor. Here we review the current knowledge on the functional role of miR-155 in the control of various cancers.

MicroRNAs-role in lung cancer

Regulation of gene expression is essential for normal physiological functions; thus deregulation of gene expression is common in disease conditions. One level of regulation of gene expression is performed by noncoding RNAs, among which microRNAs (miRNA) are the best studied. Abnormal expression of these molecular players can lead to pathogenic processes such as heart disease, immune system abnormalities, and carcinogenesis, to name but a few. Of a length of 18–25 nucleotides miRNAs are involved in binding partial complementary sequences within the 3′-UTR (3′-untranslated region) of the target mRNAs. Depending on the type of neoplastic transformation, miRNAs can act both as oncogenes (oncomirs) or as tumor suppressors. Because of the great importance of miRNAs, most researches focus on either their role as biomarkers or their potential as therapeutic targets. Herein, we present the review of microRNA biology, function, and tumorigenic potential with emphasis on their role in lung cancer.

Tumor Protein p63/microRNA Network in Epithelial Cancer Cells

Non-coding microRNAs are involved in multiple regulatory mechanisms underlying response of cancer cells to stress leading to apoptosis, cell cycle arrest and autophagy. Many molecular layers are implicated in such cellular response including epigenetic regulation of transcription, RNA processing, metabolism, signaling. The molecular interrelationship between tumor protein (TP)-p53 family members and specific microRNAs is a key functional network supporting tumor cell response to chemotherapy and potentially playing a decisive role in chemoresistance of human epithelial cancers. TP63 was shown to modulate the expression of numerous microRNAs involved in regulation of epithelial cell proliferation, differentiation, senescence, "stemness" and skin maintenance, epithelial/ mesenchymal transition, and tumorigenesis in several types of epithelial cancers (e.g. squamous cell carcinoma, ovarian carcinoma, prostate carcinoma, gastric cancer, bladder cancer, and breast tumors), as well as in chemoresistance of cancer cells. TP63/microRNA network was shown to be involved in cell cycle arrest, apoptosis, autophagy, metabolism and epigenetic transcriptional regulation, thereby providing the groundwork for novel chemotherapeutic venues.

Post-transcriptional controls by ribonucleoprotein complexes in the acquisition of drug resistance

Acquisition of drug resistance leads to failure of anti-cancer treatments and therapies. Although several successive chemotherapies are available, along with efforts towards clinical applications of new anti-cancer drugs, it is generally realized that there is a long way to go to treat cancers. Resistance to anti-cancer drugs results from various factors, including genetic as well as epigenetic differences in tumors. Determining the molecular and cellular mechanisms responsible for the acquisition of drug resistance may be a helpful approach for the development of new therapeutic strategies to overcome treatment failure. Several studies have shown that the acquisition of drug resistance is tightly regulated by post-transcriptional regulators such as RNA binding proteins (RBPs) and microRNAs (miRNAs), which change the stability and translation of mRNAs encoding factors involved in cell survival, proliferation, epithelial-mesenchymal transition, and drug metabolism. Here, we review our current understanding of ribonucleoprotein complexes, including RBPs and miRNAs, which play critical roles in the acquisition of drug resistance and have potential clinical implications for cancer.

Friend or foe: the role of microRNA in chemotherapy resistance

Chemotherapy has been widely used in treating cancer patients. Despite the tremendous progress in cancer treatment achieved during the last decades, drug resistance still accounts for most of the tumor relapses in chemotherapy-treated patients. Emerging evidence shows that microRNAs play an important role in regulating the drug sensitivity of tumor cells. However, the mechanism of microRNA-mediated drug resistance is not fully understood. Current data suggest that microRNAs can be categorized as oncogenic or tumor-suppressive based on their functions and targets. In tumor cells undergoing drug treatment, microRNAs can function either by decreasing expression of genes associated with multiple drug resistance or by promoting escape from apoptosis and inducing tumor stem cell development. This review aims to provide an updated understanding of the role of microRNAs in regulating chemotherapy resistance and a discussion of potential therapeutic applications.

microRNAs as pharmacological targets in cancer

The survival rate of cancer patients has increased considerably in the last 20 years owing to significant efforts made in prevention, early detection protocols, combined chemotherapy regimens, targeted therapies, refined radiotherapy and cancer vaccines. However, metastasis and acquired resistance to current therapies represent two major challenges for achieving long-term cure. Therefore, new treatment strategies must be developed. One promising alternative is epigenetic-based therapies, of which miRNAs are at the forefront. MicroRNAs are endogenous small non-coding RNAs, often deregulated in cancer, which regulate gene expression by specific binding to the 3'-UTR of target genes. They are excellent candidates for therapy since miRNAs can regulate multiple targets of the same or different pathways, thereby minimizing the risk of resistance development or compensatory mechanisms. In this review, the mechanisms that lead to miRNA deregulation in cancer, their feasibility as therapeutic tools and the different strategies for the pharmacological manipulation of miRNAs in preclinical animal models are discussed.