OncomiR or Tumor Suppressor? The Duplicity of MicroRNAs in Cancer

Roles of microRNA-330 and Its Target Gene ING4 in the Development of Aggressive Phenotype in Hepatocellular Carcinoma Cells

BACKGROUND

Aberrant expression of microRNAs contributes to tumor growth and progression.

AIMS

This study was designed to explore the prognostic and biological significance of miR-330 in hepatocellular carcinoma (HCC).

METHODS

The expression of miR-330 and its associations with tumor parameters and overall survival were analyzed in HCC patients. The biological functions of miR-330 in HCC cell growth, invasion, and tumorigenesis were investigated. Bioinformatic analysis and luciferase reporter assays were performed to search for potential targets of miR-330.

RESULTS

The miR-330 level was significantly higher in HCCs than in adjacent normal tissues (P = 0.0085). High expression of miR-330 was significantly associated with more aggressive phenotypes and shorter overall survival in HCC. Loss- and gain-of-function studies indicated the favorable effect of miR-330 on tumor cell growth, invasion, and tumorigenesis. Inhibitor of growth 4 (ING4) was identified to be a direct target of miR-330. Overexpression of miR-330 reduced the expression of ING4 in HCC cells. Importantly, restoration of ING4 almost completely reversed the promotion of HCC cell proliferation and invasion by miR-330.

CONCLUSIONS

Altogether, this study demonstrates that upregulation of miR-330 is associated with poor prognosis and contributes to more aggressive phenotypes of HCC. The oncogenic role of miR-330 in HCC is linked to downregulation of ING4.

Role of microRNAs in translation regulation and cancer

MicroRNAs (miRNAs) are pervasively expressed and regulate most biological functions. They function by modulating transcriptional and translational programs and therefore they orchestrate both physiological and pathological processes, such as development, cell differentiation, proliferation, apoptosis and tumor growth. miRNAs work as small guide molecules in RNA silencing, by negatively regulating the expression of several genes both at mRNA and protein level, by degrading their mRNA target and/or by silencing translation. One of the most recent advances in the field is the comprehension of their role in oncogenesis. The number of miRNA genes is increasing and an alteration in the level of miRNAs is involved in the initiation, progression and metastases formation of several tumors. Some tumor types show a distinct miRNA signature that distinguishes them from normal tissues and from other cancer types. Genetic and biochemical evidence supports the essential role of miRNAs in tumor development. Although the abnormal expression of miRNAs in cancer cells is a widely accepted phenomenon, the cause of this dysregulation is still unknown. Here, we discuss the biogenesis of miRNAs, focusing on the mechanisms by which they regulate protein synthesis. In addition we debate on their role in cancer, highlighting their potential to become therapeutic targets.

Role of Nerve Growth Factor (NGF) and miRNAs in Epithelial Ovarian Cancer

Ovarian cancer is the eighth most common cancer in women worldwide, and epithelial ovarian cancer (EOC) represents 90% of cases. Nerve growth factor (NGF) and its high affinity receptor tyrosine kinase A receptor (TRKA) have been associated with the development of several types of cancer, including EOC; both NGF and TRKA levels are elevated in this pathology. EOC presents high angiogenesis and several molecules have been reported to induce this process. NGF increases angiogenesis through its TRKA receptor on endothelial cells, and by indirectly inducing vascular endothelial growth factor expression. Other molecules controlled by NGF include ciclooxigenase-2, disintegrin and metalloproteinase domain-containing protein 17 (ADAM17) and calreticulin (CRT), proteins involved in crucial processes needed for EOC progression. These molecules could be modified through microRNA regulation, which could be regulated by NGF. MicroRNAs are the widest family of non-coding RNAs; they bind to 3'-UTR of mRNAs to inhibit their translation, to deadenilate or to degraded them. In EOC, a deregulation in microRNA expression has been described, including alterations of miR-200 family, cluster-17-92, and miR-23b, among others. Since the NGF-microRNA relationship in pathologies has not been studied, this review proposes that some microRNAs could be associated with NGF/TRKA activation, modifying protein levels needed for EOC progression.

Differential Expression of MicroRNAs in Hepatitis C Virus-Mediated Liver Disease Between African Americans and Caucasians: Implications for Racial Health Disparities

African Americans (AAs) have higher hepatocellular carcinoma (HCC) mortality rates than Caucasian Americans (CAs). Chronic hepatitis C virus (HCV) infection leads to cirrhosis and HCC. HCV infection is highly prevalent in the AA population compared to other racial groups. AAs are also less likely to naturally clear HCV, potentially contributing to higher prevalence of HCV. However, the explanation for this disparity is currently unknown. Circulating microRNAs (miRNAs) in the blood are emerging as biomarkers for pathological conditions. Expression analysis of miRNAs in major racial groups would be important for optimizing personalized treatment strategies. Here we assessed the differential expression of circulatory miRNAs from HCV-infected AA and CA patients. We identified increased expression of miR-146a, miR-150, and miR-155 in HCV-infected AA patient sera compared to that of CA. Further analysis demonstrated that these miRNAs were significantly elevated in AA patients diagnosed with HCV-mediated HCC. Higher expression of miR-150 was also noted in cirrhosis and HCC in AA patients, which may serve as a predictor of liver disease progression in this population. The differential expression of miRNAs suggests that these miRNAs and their target genes could be useful to gain further mechanistic insight of racial disparity associated with HCV-mediated pathogenesis.

CXCL12/CXCR4 axis induced miR-125b promotes invasion and confers 5-fluorouracil resistance through enhancing autophagy in colorectal cancer

The activation of CXCL12/CXCR4 axis is associated with potential progression of cancer, such as invasion, metastasis and chemoresistance. However, the underlying mechanisms of CXCL12/CXCR4 axis and cancer progression have been poorly explored. We hypothesized that miRNAs might be critical downstream mediators of CXCL12/CXCR4 axis involved in cancer invasion and chemoresistance in CRC. In human CRC cells, we found that the activation of CXCL12/CXCR4 axis promoted epithelial-mesenchymal transition (EMT) and concurrent upregulation of miR-125b. Overexpression of miR-125b robustly triggered EMT and cancer invasion, which in turn enhanced the expression of CXCR4. Importantly, the reciprocal positive feedback loop between CXCR4 and miR-125b further activated the Wnt/β-catenin signaling by targeting Adenomatous polyposis coli (APC) gene. There was a negative correlation of the expression of miR-125b with APC mRNA in paired human colorectal tissue specimens. Further experiments indicated a role of miR-125b in conferring 5-fluorouracil (5-FU) resistance in CRC probably through increasing autophagy both in vitro and in vivo. MiR-125b functions as an important downstream mediator upon the activation of CXCL12/CXCR4 axis that involved in EMT, invasion and 5-FU resistance of CRC. These findings shed a new insight into the role of miR-125b and provide a potential therapeutic target in CRC.

Dual-Function Polymeric HPMA Prodrugs for the Delivery of miRNA

An HPMA-based polymeric prodrug of a CXCR4 antagonist, AMD3465 (P-SS-AMD), was developed as a dual-function carrier of therapeutic miRNA. P-SS-AMD was synthesized by a copolymerization of HPMA with a methacrylamide monomer in which the AMD3465 was attached via a self-immolative disulfide linker. P-SS-AMD showed effective release of the parent AMD3465 drug following treatment with intracellular levels of glutathione (GSH). The AMD3465 was released in the cells and exhibited functional CXCR4 antagonism, demonstrated by inhibition of the CXCR4-mediated cancer cell invasion. Due to its cationic character, P-SS-AMD could form polyplexes with miRNA and mediate efficient transfection of miR-200c mimics to downregulate expression of a downstream target ZEB-1 in cancer cells. The combined P-SS-AMD/miR-200c polyplexes showed improved ability to inhibit cancer cell migration when compared with individual treatments. The reported findings validate P-SS-AMD as a dual-function delivery vector that can simultaneously deliver a therapeutic miRNA and function as a polymeric prodrug of CXCR4 antagonist.

MicroRNA-30d inhibits the migration and invasion of human esophageal squamous cell carcinoma cells via the post‑transcriptional regulation of enhancer of zeste homolog 2

The present study was carried out to investigate the expression pattern, clinical significance and biological functions of microRNA-30d (miR-30d) in esophageal carcinogenesis. Quantitative real-time PCR was performed to detect the expression levels of miR-30d in esophageal squamous cell carcinoma (ESCC) tissues and cell lines. Then, associations between miR-30d expression and various clinicopathological features of patients with ESCC were statistically evaluated. In addition, the effects of miR-30d on the migration and invasion of two human ESCC cell lines transfected with miRNA or co-transfected with miRNA mimics and the expression vector of its target gene were determined. The results revealed that the expression levels of miR-30d were markedly decreased in ESCC tissues and cell lines, comparing with the corresponding normal controls. Notably, reduced expression of miR-30d occurred more frequently in ESCC patients with positive lymph node metastasis, moderate-poor differentiation and advanced tumor-node-metastasis stage than those with negative features. Functionally, enforced expression of miR-30d was found to inhibit cell invasion and migration of the ESCC cell lines. Luciferase reporter assay identified enhancer of zeste homolog 2 (EZH2) as a direct target gene of miR-30d. The expression level of EZH2 mRNA was negatively correlated with the expression of miR-30d in the ESCC tissues. Moreover, the inhibitory effect of miR-30d on ESCC cell motility was reversed by EZH2 overexpression. Collectively, these findings provide convincing evidence that decreased expression of miR-30d may be implicated in esophageal carcinogenesis and progression. We also confirmed miR-30d as a tumor-suppressor which may inhibit cancer cell motility by targeting EZH2, a potential therapeutic target for ESCC.

High expression of miR-16 and miR-451 predicating better prognosis in patients with gastric cancer

PURPOSE

To investigate the expression pattern of miR-16 and miR-451 and evaluate their prognostic value in 180 GC patients undergoing surgery.

METHODS

In our previous study, a panel of five circulating miRNAs (miR-16, miR-25, miR-92a, miR-451 and miR-486-5p) can be used as a potential biomarker for detecting of early-stage gastric carcinoma (GC). Tissue microarrays were constructed from 180 patients with GC after surgery. MiR-16 and miR-451 expression was detected by miRNA-locked nucleic acid in situ hybridization, and their relationship with clinicopathological parameters and overall survival was analyzed.

RESULTS

MiR-16 expression was decreased in 30.6 % (55/180) of GC, increased in 54.4 % (98/180) and unchanged in 15.0 % (27/180), compared with paracancerous normal tissue (P < 0.001). MiR-451 expression was decreased in 17.8 % (32/180), increased in 62.8 % (113/180) and unchanged in 19.4 % (35/180) of GC, compared with paracancerous normal tissue (P < 0.001).Univariate analysis indicated that low miR-16 and miR-451 expression, tumor stage, tumor status, node status and tumor size were significant negative prognostic predictors for overall survival in patients with GC (P < 0.001, P < 0.001, P = 0.002, P < 0.001 and P = 0.001, respectively). Multivariate regression analysis demonstrated that stage [hazard ratio (HR) 1.80; 95 % confidence interval (CI) 1.0-3.26; P = 0.05], low expression of miR-16 (HR 2.26; 95 % CI 1.51-3.40; P < 0.001) and miR-451 (HR 2.01; 95 % CI 1.36-2.96; P < 0.001) predicted shorter OS, while tumor status (HR 1.59; 95 % CI 0.73-3.48 P = 0.242), lymph node metastasis (HR 1.41; 95 % CI 0.71-2.82; P = 0.326) and tumor size (HR 1.53; 95 % CI 0.92-2.55; P = 0.099) were not. Moreover, patients with both miR-16 and miR-451 high expression have better OS than those with two miRNAs unchanged or low expression in GC tissues. Patients with both miR-16 and miR-451 high have better OS than patients with single miR-451 high expression.

CONCLUSIONS

High expression of miR-16 and miR-451 was associated with longer OS in GC patients. Especially patients with miR-16 and miR-451 double high expression will predict better OS. MiR-16 and miR-451 may be used as novel makers to evaluate prognosis and provide a new treatment target in GC.

MicroRNA-targeted therapeutics for lung cancer treatment

INTRODUCTION

Lung cancer is one of the leading causes of cancer-related mortality worldwide. MicroRNAs (miRNAs) are endogenous non-coding small RNAs that repress the expression of a broad array of target genes. Many efforts have been made to therapeutically target miRNAs in cancer treatments using miRNA mimics and miRNA antagonists. Areas covered: This article summarizes the recent findings with the role of miRNAs in lung cancer, and discusses the potential and challenges of developing miRNA-targeted therapeutics in this dreadful disease. Expert opinion: The development of miRNA-targeted therapeutics has become an important anti-cancer strategy. Results from both preclinical and clinical trials of microRNA replacement therapy have shown some promise in cancer treatment. However, some obstacles, including drug delivery, specificity, off-target effect, toxicity mediation, immunological activation and dosage determination should be addressed. Several delivery strategies have been employed, including naked oligonucleotides, liposomes, aptamer-conjugates, nanoparticles and viral vectors. However, delivery remains a main challenge in miRNA-targeting therapeutics. Furthermore, immune-related serious adverse events are also a concern, which indicates the complexity of miRNA-based therapy in clinical settings.

dbDEMC 2.0: updated database of differentially expressed miRNAs in human cancers

MicroRNAs (miRNAs) are often deregulated in cancer and are thought to play an important role in cancer development. Large amount of differentially expressed miRNAs have been identified in various cancers by using high-throughput methods. It is therefore quite important to make a comprehensive collection of these miRNAs and to decipher their roles in oncogenesis and tumor progression. In 2010, we presented the first release of dbDEMC, representing a database for collection of differentially expressed miRNAs in human cancers obtained from microarray data. Here we describe an update of the database. dbDEMC 2.0 documents 209 expression profiling data sets across 36 cancer types and 73 subtypes, and a total of 2224 differentially expressed miRNAs were identified. An easy-to-use web interface was constructed that allows users to make a quick search of the differentially expressed miRNAs in certain cancer types. In addition, a new function of ‘meta-profiling’ was added to view differential expression events according to user-defined miRNAs and cancer types. We expect this database to continue to serve as a valuable source for cancer investigation and potential clinical application related to miRNAs. dbDEMC 2.0 is freely available at http://www.picb.ac.cn/dbDEMC.

Lymphocyte-specific protein 1 inhibits the growth of hepatocellular carcinoma by suppressing ERK1/2 phosphorylation

Lymphocyte‐specific protein 1 (LSP1) has been reported to regulate cell biology in several human cancers including lymphoma and breast cancer. However, the functions of LSP1 in human hepatocellular carcinoma (HCC) are still unknown. In this study, we found that LSP1 expression was downregulated in HCC tissues and cell lines, and lower LSP1 expression was correlated with poor clinicopathological features including large tumor size, high Edmondson–Steiner grading and advanced tumor–node–metastasis (TNM) stage. Additionally, we demonstrated that patients with high LSP1 expression had significantly better overall survival and disease‐free survival. Moreover, LSP1 was found to be an independent factor for predicting the prognosis of HCC patients. In vitro and in vivo assays showed that overexpressing LSP1 inhibited HCC growth by inducing both apoptosis and growth arrest. Mechanistically, we found that expression of phosphorylated extracellular regulated protein kinases 1 and 2 (ERK1/2) was downregulated after LSP1 overexpression, indicating LSP1 could suppress HCC growth by inhibiting the ERK pathway in HCC cells. Taken together, these results indicate that LSP1 may serve as a prognostic marker and a potential therapeutic target in human HCC.

Epigenetic control of the tumor microenvironment

Stromal cells of the tumor microenvironment have been shown to play important roles in both supporting and limiting cancer growth. The altered phenotype of tumor-associated stromal cells (fibroblasts, immune cells, endothelial cells etc.) is proposed to be mainly due to epigenetic dysregulation of gene expression; however, only limited studies have probed the roles of epigenetic mechanisms in the regulation of stromal cell function. We review recent studies demonstrating how specific epigenetic mechanisms (DNA methylation and histone post-translational modification-based gene expression regulation, and miRNA-mediated translational regulation) drive aspects of stromal cell phenotype, and discuss the implications of these findings for treatment of malignancies. We also summarize the effects of epigenetic mechanism-targeted drugs on stromal cells and discuss the consideration of the microenvironment response in attempts to use these drugs for cancer treatment.