miR-126 functions as a tumour suppressor in human gastric cancer

AURKA promotes cell migration and invasion of head and neck squamous cell carcinoma through regulation of the AURKA/Akt/FAK signaling pathway

The present study aimed to investigate the mechanism by which Aurora kinase A (AURKA) promotes cell migration and invasion in head and neck squamous cell carcinoma (HNSCC). Transwell assays were performed to investigate the cell migration and invasion abilities of AURKA, whilst western blotting was used to analyze the protein expression in FaDu and Hep2 cells, each treated with pharmacological inhibitors. Following the inhibition of AURKA, Akt and focal adhesion kinase (FAK), the migration and invasion of the FaDu and Hep2 cells decreased. The expression of phosphorylated (p)-AURKA and p-FAK (Y397) was observed to decrease following FaDu and Hep2 cell treatment with VX-680, a small molecular inhibitor of AURKA. The expression of p-Akt and p-FAK (Y397) ceased following treatment with the Akt inhibitor triciribine. The expression of p-FAK (Y397) decreased, however, p-Akt expression did not change following treatment with the FAK inhibitor TAE226. In conclusion, AURKA activates FAK through the AURKA/Akt/FAK signaling pathway, promoting the migration and invasion of HNSCC cells, which may subsequently provide a novel approach for the treatment of HNSCC.

Non-coding RNAs in Uterine Development, Function and Disease

The major function of the uterus is to accept and provide a suitable environment for an embryo, ultimately leading the birth of offspring and successful propagation of the species. For this occur, there must be precise coordination of hormonal signalling within both the endometrial and myometrial components of this organ. Non-coding RNAs, specifically, microRNAs (miRNAs) have been shown to be essential for normal uterine development and function. Within this organ, miRNAs are proposed to fine-tune the actions of the female steroid hormones estradiol and progesterone. Not surprising, mis-expression of miRNAs has been documented in diseases of the endometrium and myometrium such as endometriosis and leiomyomas, respectively. In this chapter, I will review the current understanding on the role, regulation and function of non-coding RNAs focusing on miRNAs in both the normal physiology of the endometrium and myometrium as well as in pathologies of these tissues, namely endometriosis and leiomyomas.

MicroRNA-126 inhibits the migration and invasion of endometrial cancer cells by targeting insulin receptor substrate 1

MicroRNAs (miRs) have been demonstrated to serve important roles in the development and progression of human cancer, primarily through the direct targeting of oncogenes or tumor suppressors. It has been previously suggested that miR-126 may be associated with endometrial cancer (EC). However, the exact role of miR-126 in the migration and invasion of EC cells has not yet been studied. The present study demonstrated that the expression of miR-126 was significantly decreased in EC tissues when compared with matched normal adjacent tissues. The current study reverse transcription-quantitative polymerase chain reaction was performed in order to examine the expression level of miR-126. Wound healing and transwell assays were used to examine cell migration and invasion. A luciferase reporter assay was used to determine the targeting relationship and western blotting assay was performed to detect the protein expression. Furthermore, the overexpression of miR-126 significantly inhibited EC SKOV3 cell migration and invasion. Molecular mechanism investigation established that insulin receptor substrate 1 (IRS1) functioned as a direct miR-126 target, and its expression was negatively regulated by miR-126 at a post-transcriptional level in the SKOV3 cells. Additionally, the overexpression of IRS1 reversed the inhibitory effect of miR-126 overexpression on SKOV3 cell migration and invasion. In conclusion, the current study demonstrated that miR-126 inhibited EC cell migration and invasion, at least partially through the direct targeting of IRS1, suggesting that miR-126 may aid the treatment of EC metastasis.

miR-126: A novel regulator in colon cancer

Colon cancer is one of the most common, lethal diseases worldwide. Tumor metastasis and chemotherapy resistance are the main reasons for its poor prognosis and high fatality rate. Tumor development is thought of as one of the most complex cellular events as it is a multi-step cascading process involving infinite proliferation, invasion and immigration. Recently, increasing studies have demonstrated that microRNA-126 (miR-126) has an important role in colon cancer. The expression of miR-126 decreased significantly in colon cancer, particularly in highly metastatic cell lines. miR-126 controls tumor cell growth, metastasis and survival via inactivation of the oncogene signaling pathway, indicating that miR-126 may serve as a therapeutic target for anticancer therapy. Potentially, miR-126 was also reported to be an ideal molecular target as a novel biomarker for liver metastasis from colorectal cancer due to its changeable expression level. In the present review, the current knowledge regarding regulatory function of miR-126 is summarized along with its underlying mechanisms in colon cancer.

MicroRNA‑145 inhibits the malignant phenotypes of gastric carcinoma cells via downregulation of fascin 1 expression

MicroRNA (miR)‑145 has been demonstrated to act as a tumor suppressor, and deregulation of fascin 1 (FSCN1) has been observed in several types of human malignancy, including gastric carcinoma. However, the molecular mechanism underlying the function of miR‑145, specifically its targets in gastric carcinoma have yet to be fully elucidated. In the present study, downregulation of miR‑145 and upregulation of FSCN1 was identified in gastric carcinoma cell lines, compared with normal gastric mucosal epithelial cells. A luciferase reporter assay demonstrated that miR‑145 was able to bind to the 3'‑untranslated region of FSCN1 mRNA. Overexpression of miR‑145 led to a significant decrease in FSCN1 expression levels, whereas knockdown of miR‑145 resulted in increased FSCN1 expression levels in gastric carcinoma cells. Furthermore, overexpression of miR‑145 inhibited proliferation, migration and invasion in gastric carcinoma cells. Similar effects were also observed in gastric carcinoma cells transfected with FSCN1 small interfering RNA. In addition, overexpression of FSCN1 reversed the suppressive effects of miR‑145 upregulation on proliferation, migration and invasion in gastric carcinoma cells, suggesting that FSCN1 is indeed involved in the miR‑145‑mediated malignant phenotype of gastric carcinoma cells. The present study revealed an anti‑oncogenic role of miR‑145 in gastric carcinoma via inhibition of FSCN1, and suggested that miR‑145 may be used for the treatment of gastric carcinoma.

Dysregulation of non-coding RNAs in gastric cancer

Gastric cancer (GC) is one of the most common cancers in the world and a significant threat to the health of patients, especially those from China and Japan. The prognosis for patients with late stage GC receiving the standard of care treatment, including surgery, chemotherapy and radiotherapy, remains poor. Developing novel treatment strategies, identifying new molecules for targeted therapy, and devising screening techniques to detect this cancer in its early stages are needed for GC patients. The discovery of non-coding RNAs (ncRNAs), primarily microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), helped to elucidate the mechanisms of tumorigenesis, diagnosis and treatment of GC. Recently, significant research has been conducted on non-coding RNAs and how the regulatory dysfunction of these RNAs impacts the tumorigenesis of GC. In this study, we review papers published in the last five years concerning the dysregulation of non-coding RNAs, especially miRNAs and lncRNAs, in GC. We summarize instances of aberrant expression of the ncRNAs in GC and their effect on survival-related events, including cell cycle regulation, AKT signaling, apoptosis and drug resistance. Additionally, we evaluate how ncRNA dysregulation affects the metastatic process, including the epithelial-mesenchymal transition, stem cells, transcription factor activity, and oncogene and tumor suppressor expression. Lastly, we determine how ncRNAs affect angiogenesis in the microenvironment of GC. We further discuss the use of ncRNAs as potential biomarkers for use in clinical screening, early diagnosis and prognosis of GC. At present, no ideal ncRNAs have been identified as targets for the treatment of GC.

Reduced miR-126 expression facilitates angiogenesis of gastric cancer through its regulation on VEGF-A

miR-126 is an endothelial-specific microRNA essential for governing vascular integrity and angiogenesis. Its role in tumor angiogenesis of gastric cancer (GC) is unclear. This study aimed at determining the role of miR-126 in GC angiogenesis. Down-regulation of miR-126 was found to inversely correlate with an increased microvessel density (MVD) and vascular endothelial growth factor A (VEGF-A) expression in gastric cancer tissues. Bioinformatics analysis and luciferase reporter assay revealed that miR-126 directly targeted the 3′-untranslated region (3′-UTR) of VEGF-A mRNA. In addition, the restoration of miR-126 expression by lentivirus-miR-126 (Lenti-miR-126) transfection obviously reduced the expression of VEGF-A and the activition of its downstream genes, Akt, mTOR and Erk1/2 in gastric cancer cell lines SGC-7901, MKN-28 and MKN-45. In contrast, the down-regulation of miR-126 expression by lentivirus-anti-miR-126 (Lenti-anti-miR-126) transfection obviously up-regulated the expression of VEGF-A and its downstream signaling pathways. In vivo xenograft mice model experiments clarified the down-regulation of VEGF-A and MVD as well as inhibition of tumor growth by up-regulation of miR-126. Overall, the results from our study suggested that miR-126 could suppress tumor growth and tumor angiogenesis of GC through VEGF-A signaling, and it is a novel potential therapeutic target for GC.

The role of miRNAs in bone metastasis and their significance in the detection of bone metastasis: a review of the published data

The preferential metastasis of cancer cells to bone disrupts the process of bone remodeling and results in serious complications. Although bone imaging techniques are well established for bone metastasis diagnosis, they still have limits. Recently, small noncoding RNA molecules, called miRNAs, have become the subject of interest in many molecular pathways in relation to bone metastasis. Furthermore, studies have demonstrated the ability to distinguish normal from cancerous cells and metastatic bone tumor origin based on miRNA profiles. Here, we summarize the data on mechanisms of osteolytic and osteoblastic bone metastases supporting the involvement of miRNA changes in the bone metastatic evolution. We also focus on the available evidence regarding current clinical studies of miRNA expression in the detection of bone metastases.

MicroRNA-126 suppresses proliferation of undifferentiated (BRAF(V600E) and BRAF(WT)) thyroid carcinoma through targeting PIK3R2 gene and repressing PI3K-AKT proliferation-survival signalling pathway

BACKGROUND

The objectives of this study are to investigate the expression of miR-126 and evaluate its effect on proliferation in undifferentiated thyroid carcinoma.

METHODS

miR-126 expression of undifferentiated thyroid carcinoma cell lines 8505C (BRAF(V600E/V600E)), BHT-101 (BRAF(V600E/WT)) and MB-1 (BRAF(WT/WT)) were quantified with q-PCR. These cell lines were transiently transfected with exogenous miR-126 (mimic). Following transfection, proliferation effects were observed through MTS proliferation assay and colony formation abilities. Immunofluorescence imaging and Western blot assay were also done to check target proteins expression.

RESULTS

Under-expression (p<0.05) of miR-126 was noted in BRAF(V600E) mutated undifferentiated thyroid carcinoma cells (8505C and BHT-101), but no change in expression was noted in non BRAF(V600E) mutated undifferentiated thyroid carcinoma cells (MB-1). In addition, a 30-50% drop in proliferation ability and a 35-45% reduction in colony formation capability were noticed in miR-126 mimic transfected group when compared to control group. Furthermore, immunofluorescence images showed reduced expression of p85β and p-AKT protein in miR-126 mimic transfected cells when compared to un-transfected cells. Also, Western blot analysis revealed a 34-40% suppression of p85β protein and a 21-53% drop in active AKT kinase (p-AKT) protein in miR-126 mimic transfected group when compared to control group.

CONCLUSIONS

Expression of miR-126 was down-regulated in BRAF(V600E) mutated undifferentiated thyroid carcinoma. In addition, miR-126 was found to act as proliferation suppressor targeting PIK3R2 gene and reducing p85β (a regulatory subunit of PI3K kinase) protein translation and lower AKT kinase activity. Therefore, miR-126 could be a potential therapeutic tool in the treatment of undifferentiated thyroid carcinoma.

Prognostic Role of MicroRNA-126 for Survival in Malignant Tumors: A Systematic Review and Meta-Analysis

Background. Increasing studies found that miR-126 expression may be associated with the prognosis of cancers. Here, we performed a meta-analysis to assess the prognostic role of miR-126 in different cancers. Methods. Eligible studies were identified by searching in PubMed, Embase, the Cochrane Library, CNKI, and Wan Fang databases up to March 2015. Pooled hazard ratios (HRs) and their corresponding 95% confidence intervals (CIs) were calculated to investigate the correlation between miR-126 and survival of cancers. Results. Thirty studies including a total of 4497 participants were enrolled in this meta-analysis. The pooled results showed that high level of miR-126 was a predictor for favorable survival of carcinomas, with pooled HR of 0.77 (95% CI 0.64–0.93) for OS, 0.64 (95%CI 0.48–0.85) for DFS, and 0.70 (95% CI 0.50–0.98) for PFS/RFS/DSS. However, high level of circulating miR-126 predicted a significantly worse OS in patients with cancer (HR = 1.65, 95% CI 1.09–2.51). Conclusions. Our results indicated that miR-126 could act as a significant biomarker in the prognosis of various cancers.

miR-126-3p Inhibits Thyroid Cancer Cell Growth and Metastasis, and Is Associated with Aggressive Thyroid Cancer

BACKGROUND

Previous studies have shown that microRNAs are dysregulated in thyroid cancer and play important roles in the post-transcriptional regulation of target oncogenes and/or tumor suppressor genes.

METHODOLOGY/PRINCIPAL FINDINGS

We studied the function of miR-126-3p in thyroid cancer cells, and as a marker of disease aggressiveness. We found that miR-126-3p expression was significantly lower in larger tumors, in tumor samples with extrathyroidal invasion, and in higher risk group thyroid cancer in 496 papillary thyroid cancer samples from The Cancer Genome Atlas study cohort. In an independent sample set, lower miR-126-3p expression was observed in follicular thyroid cancers (which have capsular and angioinvasion) as compared to follicular adenomas. Mechanistically, ectopic overexpression of miR-126-3p significantly inhibited thyroid cancer cell proliferation, in vitro (p<0.01) and in vivo (p<0.01), colony formation (p<0.01), tumor spheroid formation (p<0.05), cellular migration (p<0.05), VEGF secretion and endothelial tube formation, and lung metastasis in vivo. We found 14 predicted target genes, which were significantly altered upon miR-126-3p transfection in thyroid cancer cells, and which are involved in cancer biology. Of these 14 genes, SLC7A5 and ADAM9 were confirmed to be inhibited by miR-126-3p overexpression and to be direct targets of miR-136-3p.

CONCLUSIONS/SIGNIFICANCE

To our knowledge, this is the first study to demonstrate that miR-126-3p has a tumor-suppressive function in thyroid cancer cells, and is associated with aggressive disease phenotype.

CRKL oncogene is downregulated by p53 through miR-200s

Tumor suppressive miRNAs that target oncogenes are frequently downregulated in cancers, and this downregulation leads to oncogene pathway activation. Thus, tumor suppressive miRNAs and their target oncogenes have been proposed as useful targets in cancer treatment. miR-200 family downregulation has been reported in cancer progression and metastasis. The miR-200 family consists of two gene clusters, miR-200b/200a/429 and miR-200c/141, which are located on human chromosomes 1 and 12, respectively. Here, we identified that p53 response elements are located around both clusters of the miR-200 family and confirmed that miR-200s are transcriptional targets of the p53 family. In silico analyses of miRNA targets established the CRKL oncogene as a potential target for miR-200b/200c/429. Moreover, miR-200b/200c/429 inhibited CRKL mRNA and protein expression by directly targeting its 3'-UTR region. Importantly, endogenous CRKL expression was decreased in cancer cells through the introduction of p53 family and endogenous p53 activation. Moreover, the downregulation of CRKL by siRNA inhibited cancer cell growth. The Oncomine database demonstrates that CRKL is overexpressed in a subset of cancer types. Furthermore, CRKL is significantly overexpressed in primary breast cancer tissues harboring mutant TP53. Our results demonstrate that the p53 target miR-200b/200c/429 miRNAs are negative regulators of the CRKL oncogene.

High-Throughput Sequencing of miRNAs Reveals a Tissue Signature in Gastric Cancer and Suggests Novel Potential Biomarkers

Gastric cancer has a high incidence and mortality rate worldwide; however, the use of biomarkers for its clinical diagnosis remains limited. The microRNAs (miRNAs) are biomarkers with the potential to identify the risk and prognosis as well as therapeutic targets. We performed the ultradeep miRnomes sequencing of gastric adenocarcinoma and gastric antrum without tumor samples. We observed that a small set of those samples were responsible for approximately 80% of the total miRNAs expression, which might represent a miRNA tissue signature. Additionally, we identified seven miRNAs exhibiting significant differences, and, of these, hsa-miR-135b and hsa-miR-29c were able to discriminate antrum without tumor from gastric cancer regardless of the histological type. These findings were validated by quantitative real-time polymerase chain reaction. The results revealed that hsa-miR-135b and hsa-miR-29c are potential gastric adenocarcinoma occurrence biomarkers with the ability to identify individuals at a higher risk of developing this cancer, and could even be used as therapeutic targets to allow individualized clinical management.

Effects of pitavastatin on the expression of VCAM-1 and its target gene miR-126 in cultured human umbilical vein endothelial cells

OBJECTIVES

Reducing the expression of endothelial cell adhesion molecules is conducive to the decrease of inflammation-induced vascular complications. In this study, we observed pitavastatin on expression of vascular cell adhesion molecule-1 (VCAM-1) and its influence on VCAM-1's target gene miR-126 in endothelial cells. The purpose of this study is to explore the mechanism of pitavastatin in prevention and treatment of atherosclerosis.

METHODS

HUVEC were cultured in M1640 and passages 2-5 were used in experiments. The cells were randomly divided into three groups, control, TNF-α and pitavastatin group. Cells of TNF-α group were co-incubated with different concentrations (10, 20, 30 μg/L) of TNF-α for 24 h. Cells of pitavastatin group were firstly coincubated with (0.01, 0.1, 1 μmol/L) pitavastatin, respectively, for 1 h, then coincubated with 30 μg/L TNF-α for 24 h. VCAM-1 and miR-126 mRNA were detected by RT-PCR, and Western blotting was used to detect protein expression of VCAM-1.

RESULTS

Both detection methods have showed that TNF-α stimulation significantly increased the mRNA and protein expression of VCAM-1 in a dose-dependent manner, and miR-126 mRNA expression exhibited a decreasing trend. The increase of VCAM-1 mRNA and protein expression induced by TNF-α was inhibited by pitavastatin in a dose-dependent manner, too. However, there were no differences of the expression of miR-126 among three groups.

CONCLUSIONS

These effects may explain the ability of pitavastatin to reduce the progression of atherosclerosis. The findings further suggest that inhibitory effect of pitavastatin on VCAM-1 is not related to miR-126 but depends on other ways.

MicroRNA regulons in tumor microenvironment

Cancer initiation and progression are defined by the behavior of cancer cells per se and the development of tumor tissues, both of which are modulated by crosstalk between cancer cells and the surrounding microenvironment. Advances in cancer research have highlighted the significance of constant evolution of the tumor microenvironment, leading to tumor formation, metastasis and refractoriness to therapy. MicroRNAs (miRNAs) are small non-coding RNAs that function as major players of posttranscriptional gene regulation in diverse biological processes. They function as both tumor suppressors and promoters in many aspects of the autonomous behavior of cancer cells. Theoretically, dysfunction in the gene regulatory networks of cancer cells is one of the major driving forces for alterations of ostensibly normal surrounding cells. In this context, the core targets of miRNAs, termed miRNA regulons, are currently being expanded to include various modulators of the tumor microenvironment. Recent advances have highlighted two important roles played by miRNAs in the evolution of tumor microenvironments: miRNAs in tumor cells transform the microenvironment via non-cell-autonomous mechanisms, and miRNAs in neighboring cells stabilize cancer hallmark traits. These observations epitomize the distal and proximal functions of miRNAs in tumor microenvironments, respectively. Such regulation by miRNAs affects tumor angiogenesis, immune invasion and tumor-stromal interactions. This review summarizes recent findings on the mechanisms of miRNA-mediated regulation of tumor microenvironments, with a perspective on the design of therapeutic interventions.

Tumor tissue microRNA expression in association with triple-negative breast cancer outcomes

We evaluated suggested metastasis-related microRNAs (miRNAs) for their associations with disease-free survival (DFS) and overall survival (OS) of triple-negative breast cancer (TNBC). In a cohort of 456 TNBC cases, we systematically evaluated 57 previously reported metastasis-related miRNAs in tumor tissue using the NanoString nCounter assay. Cox regression was applied to evaluate miRNA expression in association with DFS and OS. In vitro assays using the TNBC cell line MDA-MB-231 were also conducted to validate epidemiological study findings. During a median follow-up of 5.3 years, 112 deaths and 97 recurrences were documented. High levels of miR-374b-5p, miR-218-5p, or miR-126-3p, or low levels of miR-27b-3p were independently associated with a favorable TNBC outcome (P < 0.01 for all). A composite score based on the levels of these four miRNAs was associated with DFS, with hazard ratios (95 % confidence interval) of 0.70 (0.43-1.15), 0.51 (0.29-0.90), and 0.18 (0.09-0.37) for the second, third, and fourth compared to the lowest quartile. Incorporating the miRNA score with known TNBC outcome predictors, i.e., age at diagnosis, tumor stage, and basal-like subtype, increased the C-index for predicting DFS from 0.68 to 0.74. Additionally, miR-126-3p was correlated with basal-like breast cancer, and miR-374b-5p modified the therapeutic effects of 5-Fluorouracil and Cyclophosphamide treatments in basal-like breast cancer patients. Restoring miR-126-3p, miR-218-5p, or miR-374b-5p, or inhibiting miR-27b-3p in MDA-MB-231 cells reduced cell proliferation. miR-374b-5p suppressed cell invasion and miR-218-5p inhibited colonization. This study provides strong evidence that the expression levels of miR-374b-5p, miR-27b-3p, miR-126-3p, and miR-218-5p in tumor tissues predict TNBC outcomes.

Phosphatidylinositol transfer proteins and instructive regulation of lipid kinase biology

Phosphatidylinositol is a metabolic precursor of phosphoinositides and soluble inositol phosphates. Both sets of molecules represent versatile intracellular chemical signals in eukaryotes. While much effort has been invested in understanding the enzymes that produce and consume these molecules, central aspects for how phosphoinositide production is controlled and functionally partitioned remain unresolved and largely unappreciated. It is in this regard that phosphatidylinositol (PtdIns) transfer proteins (PITPs) are emerging as central regulators of the functional channeling of phosphoinositide pools produced on demand for specific signaling purposes. The physiological significance of these proteins is amply demonstrated by the consequences that accompany deficits in individual PITPs. Although the biological problem is fascinating, and of direct relevance to disease, PITPs remain largely uncharacterized. Herein, we discuss our perspectives regarding what is known about how PITPs work as molecules, and highlight progress in our understanding of how PITPs are integrated into cellular physiology. This article is part of a Special Issue entitled Phosphoinositides.

Effects and mechanism of miR-214 on hepatocellular carcinoma

OBJECTIVE

To explore the role of miR-214 in the progression of hepatocellular carcinoma (HCC) and its inhibitory mechanisms in depressing the signaling pathway of β-catenin, this study was conducted.

METHODS

We ectopically expressed miR-214 in HepG2 cells to obtain cell lines Lv-miR-214-HepG2 and their control Lv-control-HepG2. Differences between the two cell lines were compared in cell growth, proliferation, colony forming ability and cell cycles. RT-PCR method was applied for the quantification of β-catenin mRNA expression. Western-blot method was applied for the determination of the protein level of β-catenin and their downstream targets (ie. Cyclin D1, c-Myc and TCF-1). The effect of miR-214 on cells was further explored through RNA interference and restoring miR-214 expression.

RESULTS

In comparison with negative (Lv-control-HepG2) and blank (HepG2) control, a significant inhibition of cell growth and proliferation caused by miR-214 was observed after 48∼72h of cell culture experiments (P<0.05). The miR-214 treatment resulted in a colony forming efficiency of (23.28±3.26)%, which was significantly lower than that of negative control [(51.31±3.97)%] (P<0.05). According to FCM results, the experimental group, compared with control, showed a higher proportion of cells in G0/G1 phase [(70.32±3.12)%] but a lower proportion in S phase [(18.42±2.90)%] (P<0.05). The MTT assay demonstrated a significant inhibition of the proliferation and β-catenin expression of HCC cells compared with control (P<0.05), while no significant difference was observed after HCC cells being transfected with β-catenin overexpression plasmid (P>0.05). By comparing to the RT-PCR and Western-blot results of control, the miR-214 treatment led to a slightly decrease in the β-catenin mRNA expression (P>0.05), but an extremely inhibition in the protein level of β-catenin and its downstream targets Cyclin D1, c-Myc, and TCF-1 (P<0.05).

CONCLUSIONS

miR-214 functions as a suppressor during the progression of HCC, and its inhibitory role was achieved by down-regulating β-catenin signaling pathway.

MicroRNA-126 inhibits cell proliferation in gastric cancer by targeting LAT-1

MicroRNA-126 (miR-126) is a pivotal post-transcriptional regulator, which has been validated as a suppressor in gastric cancer (GC). However, the downstream of its tumor inhibiting function has not been totally clear. L-type amino-acid transporter 1 (LAT-1) is a novel member of system L-type transporters involving in cell proliferation, and we have previously validated that LAT-1 played a role of promotor in GC. In this study, we further detected and confirmed that LAT-1 was exactly targeted by miR-126 in GC. We found LAT-1 was significantly downregulated in GC MKN-45 cell lines by using miR-126 mimics, along with an impairment on cell proliferation and cell cycle. Additionally, by overexpressing LAT-1 in MKN-45 cells which was firstly treated with miR-126 mimics, the ability of cell proliferation in MKN-45 cells was definitely rescued. Thus, our results suggests and consolidates the standpoint that miR-126 plays a pivotal role in GC suppressing the process of GC cell, and this function is at least partly taken to implement by miR-126s's post-transcriptional effect on LAT-1. This might provide us likely potential biomarkers and targets for GC prevention, diagnosis and therapeutic treatment.

Identification of reference microRNAs for quantitative expression analysis in porcine peripheral blood mononuclear cells treated with polyinosinic-polycytidylic acid

Peripheral blood mononuclear cells (PBMCs) are clinically important cells. Detection of microRNAs (miRNAs) expression in PBMCs can be useful for miRNA biomarker discovery for various diseases. Quantitative real-time PCR (qRT-PCR) has become an important method used for measuring miRNAs expression. However, the reliability of qRT-PCR data critically depends on proper selection of reference genes. Here, we performed qRT-PCR to quantify the expression levels of nine miRNAs (Ssc-miR-16, Hsa-miR-25, Ssc-miR-34a, Hsa-miR-93, Bta-miR-92b, Ssc-miR-103, Ssc-miR-106a, Ssc-miR-128 and Ssc-miR-107) and one small nuclear RNA (U6) in PBMCs treated with polyinosinic-polycytidylic acid [poly (I:C)] that widely used for simulating viral infection. We used the four statistical algorithms (GeNorm 3.5, NormFinder, BestKeeper and comparative ∆ Ct method) to evaluate gene expression stability and observed that Ssc-miR-34a was the best single reference gene and the pair of Ssc-miR-107 and Ssc-miR-103 was the best combination of reference miRNAs for porcine PBMCs treated with poly (I:C). Our study shows the first evidence of careful selection of reference miRNAs in porcine PBMCs and maybe helpful for discovering miRNA biomarkers for double-stranded RNA-induced disease.

microRNA-126 suppresses PAK4 expression in ovarian cancer SKOV3 cells

Primary ovarian cancer is one of the predominant causes of mortality from gynecological cancer. The suppression of serine/threonine p21-activated kinases (PAKs), proteins involved in cell morphology and cytoskeletal reorganization, has been hypothesized to improve the survival of patients with ovarian cancer. However, the association between microRNA-126 (miR-126) and PAK4 in the inhibition of ovarian cancer cell invasion remains to be established. The present study demonstrated changes in the level of PAK4 expression in ovarian cancer SKOV3 cells with altered miR-126 compared with normal SKOV3 cells. The SKOV3 cells that were transfected with LV3-miR-126 to increase miR-126 expression exhibited significantly downregulated expression levels of PAK4 (P<0.05), whilst transfection with the LV3-hsa-miR-126 inhibitor increased the expression of PAK4 in these cells (P<0.05), as assessed by immunofluorescence staining. Furthermore, western blot analysis revealed a significant increase in PAK4 expression in the SKOV3 cells transfected with the LV3-hsa-miR-126 inhibitor, and a decrease in those transfected with LV3-hsa-miR-126. The present study provides an experimental foundation for miR-126 as a potential tumor suppressor that may decrease PAK4 expression to inhibit ovarian cancer cells.

MiR-199a-3p promotes gastric cancer progression by targeting ZHX1

Accumulating evidence has indicated that microRNAs (miRNAs) act as critical epigenetic regulators in tumor carcinogenesis. Here, we report that miR-199a-3p was significantly upregulated in gastric cancer (GC) cell lines and tissues. Functional studies demonstrated that miR-199a-3p dramatically increased cell proliferation and suppressed cell apoptosis both in vitro and in vivo. Furthermore, the transcriptional regulator zinc fingers and homeoboxes 1 (ZHX1) was identified as one of the direct downstream targets of miR-199a-3p, miR-199a-3p bound to the ZHX1 3′ untranslated region (3′UTR) to regulate ZHX1 protein expression. In addition, the expression of miR-199a-3p was inversely associated with that of ZHX1 in GC cell lines. Overexpression of miR-199a-3p in SGC-7901 cells inhibited ZHX1 expression, while reduction in miR-199a-3p by inhibitors in NCI-N87 cells enhanced ZHX1 expression. Moreover, restoring ZHX1 expression in SGC-7901/miR-199a-3p cells inhibited the cell proliferation induced by miR-199a-3p. Taken together, these findings suggest that miR-199a-3p may function as a novel tumor promoter in GC and its oncogenic activity may involve the direct targeting and inhibition of ZHX1.

Regulation of cancer metastasis by microRNAs

MicroRNAs (miRNAs) are a class of endogenous small non-coding RNAs that have been found highly conserved among species. MiRNAs are able to negatively regulate gene expression through base pairing of 3' UTRs of their target genes. Therefore, miRNAs have been shown to play an important role in regulating various cellular activities. Over the past decade, substantial evidences have been obtained to show that miRNAs are aberrantly expressed in human malignancies and could act as "OncomiRs" or "Tumor suppressor miRs". In recent years, increasing number of studies have demonstrated the involvement of miRNAs in cancer metastasis. Many studies have shown that microRNAs could directly target genes playing a central role in epithelia-mesenchymal-transition (EMT), a cellular transformation process that allows cancer cells to acquire motility and invasiveness. EMT is considered an essential step driving the early phase of cancer metastasis. This review will summarize the recent findings and characterization of miRNAs that are involved in the regulation of EMT, migration, invasion and metastasis of cancer cells. Lastly, we will discuss potential use of miRNAs as diagnostic and prognostic biomarkers as well as therapeutic targets for cancer.

miR-126 Suppresses the proliferation of cervical cancer cells and alters cell sensitivity to the chemotherapeutic drug bleomycin

In cervical cancer, one of the most common malignant tumors in women worldwide, miR-126 has been reported to exhibit decreased expression. However, its role in cervical cancer cell proliferation and drug sensitivity has remained relatively unexplored. Here, we compared the expression of miR-126 in cervical cancer tissues (n = 20) with that in normal cervical tissue (n = 20) using quantitative RT-PCR. The viability of Siha cervical cancer cells was further measured by MTT assay after transfection with miR-126 mimic (Siha-miR-126 mimic) or microRNA mimic negative control (Siha-miR mimic NC) and after treatment with various concentrations of bleomycin (BLM). IC50s were calculated, and the survival rates (SRs) of Siha cells were calculated. miR-126 expression in cervical cancer tissue was significantly decreased compared with that in normal cervical tissue (P < 0.01). The relative SRs of Siha-miR-126 mimic cells were also significantly decreased compared with those of Siha-miR mimic NC cells at 24-96 h after transfection. The IC50 of BLM in Siha-miR-126 mimic cells (50.3 ± 2.02 μg/mL) was decreased compared with that in Siha-miR mimic NC cells (70.5 ± 4.33 μg/mL) at 48 h after transfection (P < 0.05). Finally, the SRs of Siha-miR-126 mimic cells were significantly lower than those of Siha- miR mimic NC cells after cultured in medium containing 40 μg/mL BLM for 24-96 h (P < 0.05). These results suggest that miR-126 is expressed at low levels in cervical cancer. Upregulation of miR-126 inhibited cervical cancer cell proliferation and enhanced the sensitivity to BLM. Thus, miR-126 may represent a novel approach to cervical cancer treatment.

Cancer type-specific epigenetic changes: gastric cancer

Gastric cancer (GC) remains a major cause of mortality despite declining rate in the world. Epigenetic alterations contribute significantly to the development and progression of gastric tumors. Epigenetic refers to the number of modifications of the chromatin structure that affect gene expression without altering the primary sequence of DNA, and these changes lead to transcriptional activation or silencing of the gene. Over the years, the study of epigenetic processes has increased, and novel therapeutic approaches have emerged. This chapter summarizes the main epigenomic mechanisms described recently involved in gastric carcinogenesis, focusing on the roles that aberrant DNA methylation, histone modifications (histone acetylation and methylation), and miRNAs (oncogenic and tumor suppressor function of miRNA) play in the onset and progression of gastric tumors. Clinical implications of these epigenetic alterations in GC are also discussed.

microRNAs Distinctively Regulate Vascular Smooth Muscle and Endothelial Cells: Functional Implications in Angiogenesis, Atherosclerosis, and In-Stent Restenosis

Endothelial cells (EC) and vascular smooth muscle cells (VSMC) are the main cell types within the vasculature. We describe here how microRNAs (miRs)--noncoding RNAs that can regulate gene expression via translational repression and/or post-transcriptional degradation--distinctively modulate EC and VSMC function in physiology and disease. In particular, the specific roles of miR-126 and miR-143/145, master regulators of EC and VSMC function, respectively, are deeply explored. We also describe the mechanistic role of miRs in the regulation of the pathophysiology of key cardiovascular processes including angiogenesis, atherosclerosis, and in-stent restenosis post-angioplasty. Drawbacks of currently available therapeutic options are discussed, pointing at the challenges and potential clinical opportunities provided by miR-based treatments.

The emerging role of miRNAs in inflammatory bowel disease: a review

Inflammatory bowel disease (IBD), comprised of ulcerative colitis and Crohn's disease, is believed to develop as a result of a deregulated inflammatory response to environmental factors in genetically susceptible individuals. Despite advances in understanding the genetic risks of IBD, associated single nucleotide polymorphisms have low penetrance, monozygotic twin studies suggest a low concordance rate, and increasing worldwide IBD incidence leave gaps in our understanding of IBD heritability and highlight the importance of environmental influences. Operating at the interface between environment and heritable molecular and cellular phenotypes, microRNAs (miRNAs) are a class of endogenous, small noncoding RNAs that regulate gene expression. Studies to date have identified unique miRNA expression profile signatures in IBD and preliminary functional analyses associate these deregulated miRNAs to canonical pathways associated with IBD pathogenesis. In this review, we summarize and discuss the miRNA expression signatures associated with IBD in tissue and peripheral blood, highlight miRNAs with potential future clinical applications as diagnostic and therapeutic targets, and provide an outlook on how to develop miRNA based therapies.

Decreased expression of microRNA-126 is associated with poor prognosis in patients with cervical cancer

Background

MicroRNA-126(miR-126) has been shown to be frequently down-regulated in a variety of malignancies and act as a potential tumor suppressor. However, its correlations with the clinicopathological characters of cervical cancer remain unclear.

Methods

TaqMan quantitative RT-PCR was used to determine the expression level of miR-126 in tissue samples. The associations of miR-126 expression with clinicopathologic variables were analyzed. Kaplan-Meier survival analysis was performed to analyze the association of miR-126 expression with overall survival (OS) of patients. Univariate and multivariate Cox regression analyses were performed.

Results

miR-126 expression level in human cervical cancer tissues was significantly lower than that in adjacent nontumorous tissues (mean ± SD: 0.59 ± 0.44 vs. 1.00 ± 0.51, P < 0.0001). Decreased miR-126 expression in cervical cancer was found to be significantly associated with lymphatic invasion (P = 0.002), distant metastasis (P < 0.001), FIGO stage (P = 0.009), and histological grade (P = 0.005). Kaplan-Meier analysis showed that patients with lower levels of miR-126 had significantly poorer survival than those with higher expression of this miRNA in patients, with a 5-year OS of 45.7% and 70.9%, respectively (P = 0.002). Multivariate analysis revealed that miR-126 expression (HR = 3.97, 95% CI: 2.01-20.22; P = 0.003) was independently associated with the OS.

Conclusion

Our data suggests the potential of miR-126 as a prognostic biomarker for cervical cancer.

Virtual Slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2014_220

miR-374a promotes cell proliferation, migration and invasion by targeting SRCIN1 in gastric cancer

MicroRNAs (miRNAs) play a prominent role in gastric cancer (GC) initiation and progression. In this study, we found that miR-374a expression was up-regulated in human GC cell lines and tissues. Inhibition of miR-374a suppressed GC cell proliferation, migration and invasion in vitro and slowed tumor growth in vivo. SRC kinase signaling inhibitor 1 (SRCIN1) was identified as a direct target of miR-374a. Silencing of SRCIN1 significantly enhanced cell proliferation, migration and invasion, whereas SRCIN1 reintroduction partially abrogated the oncogenic effects of miR-374a. Taken together, these findings suggest that miR-374a functions as a candidate oncogene in GC by directly targeting SRCIN1. miR-374a may therefore be useful as a promising therapeutic target for malignant GC.

Silencing of polo-like kinase 2 increases cell proliferation and decreases apoptosis in SGC-7901 gastric cancer cells

Polo‑like kinase 2 (PLK2) is a serine/threonine protein kinase, which has vital roles during mitosis and the centrosome cycle. In acute myeloblastic leukemia and hepatocarcinogenesis, PLK2 acts as a tumor suppressor; however, the function of PLK2 in gastric cancer remains to be elucidated. In the present study, PLK2 was overexpressed in gastric cancer tissues and three types of gastric cancer cells, SGC‑7901, MKN‑45 and BGC‑823. Transfection of SGC‑7901 gastric cancer cells with small interfering (si)RNA against PLK2 exerted no effect on the ratio of cells at different stages of the cell cycle compared with that of the untransfected and control siRNA‑transfected cells. In addition, silencing of PLK2 significantly enhanced the growth of SGC‑7901 cells through inhibiting apoptosis. Furthermore, apoptosis‑associated genes Bax and caspase 3 were found to be downregulated at the protein level. In conclusion, these results suggested that PLK2 may act as a tumor suppressor in gastric cancer, therefore indicating its therapeutic potential.

MicroRNA-126 suppresses mesothelioma malignancy by targeting IRS1 and interfering with the mitochondrial function

AIMS

MiR126 was found to be frequently lost in many types of cancer, including malignant mesothelioma (MM), which represents one of the most challenging neoplastic diseases. In this study, we investigated the potential tumor suppressor function of MiR126 in MM cells. The effect of MiR126 was examined in response to oxidative stress, aberrant mitochondrial function induced by inhibition of complex I, mitochondrial DNA (mtDNA) depletion, and hypoxia.

RESULTS

MiR126 was up-regulated by oxidative stress in nonmalignant mesothelial (Met5A) and MM (H28) cell lines. In Met5A cells, rotenone inhibited MiR126 expression, but mtDNA depletion and hypoxia up-regulated MiR126. However, these various stimuli suppressed the levels of MiR126 in H28 cells. MiR126 affected mitochondrial energy metabolism, reduced mitochondrial respiration, and promoted glycolysis in H28 cells. This metabolic shift, associated with insulin receptor substrate-1 (IRS1)-modulated ATP-citrate lyase deregulation, resulted in higher ATP and citrate production. These changes were linked to the down-regulation of IRS1 by ectopic MiR126, reducing Akt signaling and inhibiting cytosolic sequestration of Forkhead box O1 (FoxO1), which promoted the expression of genes involved in gluconeogenesis and oxidative stress defense. These metabolic changes induced hypoxia-inducible factor-1α (HIF1α) stabilization. Consequently, MiR126 suppressed the malignancy of MM cells in vitro, a notion corroborated by the failure of H28(MiR126) cells to form tumors in nude mice.

INNOVATION AND CONCLUSION

MiR126 affects mitochondrial energy metabolism, resulting in MM tumor suppression. Since MM is a fatal neoplastic disease with a few therapeutic options, this finding is of potential translational importance.

Characterization of the microRNA expression profile of cervical squamous cell carcinoma metastases

OBJECTIVES

MicroRNAs (miRNAs) are important regulators of many physiological and pathological processes, including tumorigenesis and metastasis. In this study, we sought to determine the underlying molecular mechanisms of metastatic cervical carcinoma by performing miRNA profiling.

METHODS

Tissue samples were collected from ten cervical squamous cancer patients who underwent hysterectomy and pelvic lymph node (PLN) dissection in our hospital, including four PLN-positive (metastatic) cases and six PLN-negative (non-metastatic) cases. A miRNA microarray platform with 1223 probes was used to determine the miRNA expression profiles of these two tissue types and case groups. MiRNAs having at least 4-fold differential expression between PLN-positive and PLN-negative cervical cancer tissues were bioinformatically analyzed for target gene prediction. MiRNAs with tumor-associated target genes were validated by quantitative reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

Thirty-nine miRNAs were differentially expressed (>4-fold) between the PLN-positive and PLN-negative groups, of which, 22 were up-regulated and 17 were down-regulated. Sixty-nine percent of the miRNAs (27/39) had tumor-associated target genes, and the expression levels of six of those (miR-126, miR-96, miR-144, miR-657, miR-490-5p, and miR-323-3p) were confirmed by quantitative (q)RT-PCR.

CONCLUSIONS

Six MiRNAs with predicted tumor-associated target genes encoding proteins that are known to be involved in cell adhesion, cytoskeletal remodeling, cell proliferation, cell migration, and apoptosis were identified. These findings suggest that a panel of miRNAs may regulate multiple and various steps of the metastasis cascade by targeting metastasis-associated genes. Since these six miRNAs are predicted to target tumor-associated genes, it is likely that they contribute to the metastatic potential of cervical cancer and may aid in prognosis or molecular therapy.

Expression of miRNAs in non-small-cell lung carcinomas and their association with clinicopathological features

Lung cancer is recognized as a leading cause of cancer-related deaths worldwide. Over the past several years, evidence emerged that microRNAs (miRNAs), a class of small non-coding RNA molecules regulating gene expression at posttranscriptional level, play an important role in cell functioning, as well as in human diseases. Here, we analyzed expression of miR-15a/16, miR-21, miR-34a, miR-126, miR-128, and miR-210 at transcriptional level in 30 non-small-cell lung carcinoma (NSCLC) tumor tissues compared to the matched adjacent normal tissues and their correlation with clinicopathological features of the patients. Samples were collected from the NSCLC patients undergoing surgery before radiotherapeutic or chemotherapeutic treatment. Expression levels of miRNAs were assessed by TaqMan RT-PCR assay. The data obtained in this study were processed using REST 2009 and SPSS statistical software. The graphs were designed by GraphPad prism 5.0. In tumor samples, we found downregulation of miR-15a/16 (50/83.3%), miR-34a (83.3%), miR-126 (70%), and miR-128 (63.3%). At the same time, miR-21 and miR-210 were upregulated by 53.3 and 66.6% in cancer tissue versus matched adjacent normal tissues, respectively. No significant correlation was found between the expression levels of miR-15a/16, miR-21, miR-34a, miR-126, miR-128, and miR-210 and lymph node, tumor size, sex, and smoking. However, the study demonstrated a correlation between a change in expression of miR-15, miR-16, miR-34a, miR-126, and miR-210 compared to normal tissues and TNM staging (P < 0.05). Furthermore, miR-126 expression level was different in adenocarcinomas and squamous cell carcinoma (SCC) subtype (P < 0.1). Detailed analysis revealed significant change in expression of miR-15a/16, miR-34a, miR-126, and miR-210 in NSCLC tumor samples indicating involvement of these miRNAs in lung cancer pathogenesis. miR-210 demonstrated the most consistent increase in tumor tissues between different patients, suggesting its potential significance for NSCLC.

Oncogenic activity of the regulatory subunit p85β of phosphatidylinositol 3-kinase (PI3K)

Expression of the regulatory subunit p85β of PI3K induces oncogenic transformation of primary avian fibroblasts. The transformed cells proliferate at an increased rate compared with nontransformed controls and show elevated levels of PI3K signaling. The oncogenic activity of p85β requires an active PI3K-TOR signaling cascade and is mediated by the p110α and p110β isoforms of the PI3K catalytic subunit. The data suggest that p85β is a less effective inhibitor of the PI3K catalytic subunit than p85α and that this reduced level of p110 inhibition accounts for the oncogenic activity of p85β.

Crk at the quarter century mark: perspectives in signaling and cancer

The Crk adaptor protein, discovered 25 years ago as the transforming gene (v-crk) product encoded by the CT10 avian retrovirus, has made a great impact on the field of signal transduction. By encoding an oncoprotein that contained a viral gag protein fused to only SH2 and SH3 domains, v-Crk demonstrated the significance of SH2 and SH3 domains in oncogenic signaling by their virtue of binding in a sequence-specific context to organize and assemble protein networks. In more recent years, the cellular homologs of Crk (Crk II, Crk I, and CrkL) have been extensively studied, and shown to have critical functions in a wide spectrum of biological and pathological processes that include cell motility, invasion, survival, bacterial pathogenesis, and the efferocytosis of apoptotic cells. Clinically, Crk proteins are implicated in the aggressive behavior of human cancers, including adenocarcinomas of the lung, breast, and stomach, as well as in sarcomas and gliomas. Over-expression of Crk proteins in human cancers has led to a renewed interest in both their signal transduction pathways and mechanisms of up-regulation. This prospect summarizes recent developments in Crk biology, including new structural and biochemical roles for the atypical carboxyl-terminal SH3 (SH3C) domain, revelations regarding the molecular differences between Crk II and Crk L, and the significance of Crk expression in stratified human tumor samples.

MiR-126-3p suppresses tumor metastasis and angiogenesis of hepatocellular carcinoma by targeting LRP6 and PIK3R2

Background

The deregulation of microRNAs has been reported to play a pivotal role in hepatocellular carcinoma (HCC). MiR-126-3p has been reported to be associated with poor prognosis in HCC. However the underlying mechanism of miR-126-3p in HCC remains unclear.

Methods

The expression levels of miR-126-3p in HCC tissues and cells were detected by RT-PCR. Transwell assay and capillary tube formation assay were applied to assess the metastasis and angiogenesis in vitro. Nude mice subcutaneous tumor model was used to perform in vivo study. Dual- luciferase reporter assay was conducted to confirm the direct binding of miR-126-3p and target genes. The changes of biomarker protein levels were examined by western blot and Immunohistochemistry.

Results

We observed that the miR-126-3p expression levels in HCC tissues and cells were significantly down-regulated. Through gain- and loss- of function studies, we showed that miR-126-3p dramatically inhibited HCC cells from migrating and invading extracellular matrix gel and suppressed capillary tube formation of endothelial cells in vitro. Furthermore, overexpression of miR-126-3p significantly reduced the volume of tumor and microvessel density in vivo. LRP6 and PIK3R2 were identified as targets of miR-126-3p. Silencing LRP6 and PIK3R2 had similar effects of miR-126-3p restoration on metastasis and angiogenesis individually in HCC cells. Furthermore, the miR-126-3p level was inversely correlated with LRP6 and PIK3R2 in HCC tissues. In addition, the rescue experiments indicated that the metastasis and angiogenesis functions of miR-126-3p were mediated by LRP6 and PIK3R2.

Conclusion

Our results demonstrates that deregulation of miR-126-3p contributes to metastasis and angiogenesis in HCC. The restoration of miR-126-3p expression may be a promising strategy for HCC therapy.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-014-0259-1) contains supplementary material, which is available to authorized users.

miRNAs in human papilloma virus associated oral and oropharyngeal squamous cell carcinomas

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer in the world with 600,000 new cases diagnosed annually. Tobacco and alcohol use have been associated as the principal etiological factors of this pathogenesis. The incidence of smoking-associated HNSCC has declined, while human papilloma virus (HPV)-associated HNSCC is on the rise. There are currently no clinically validated biomarkers to detect this cancer at an early stage (cancers independent of HPV status). It is well-established that the aberrant expression of miRNAs can lead to tumorigenesis. miRNA expression differences have also been demonstrated in HPV-positive and HPV-negative HNSCC tumor tissues as well as in body fluids. Therefore, miRNAs have the potential to provide an unprecedented insight into the pathogenesis of HNSCC and serve as potential biomarkers. This review addresses HNSCC disease burden and the regulation of miRNA by HPV viral oncoproteins, potential miRNA biomarkers and future perspectives. miRNA provides an unique opportunity to fulfill the current clinical challenge in HNSCC patient management by enabling early detection followed by targeted interventions, leading to a significant reduction in mortality and morbidity.

MiRNA as potential biomarkers and therapeutic targets for gastric cancer

Gastric cancer is one of the leading causes of cancer mortality in the world. Aberrant expression of microRNAs (miRNAs) is the hallmark of this disease. MiRNAs are endogenous non-coding RNAs that are involved in many biological processes (e.g., cell proliferation, differentiation, apoptosis, invasion and development) through gene repression. Deregulation of miRNA expression in gastric tumors and cancer cell lines have been documented to contribute in tumorigenesis, and the expression signature may correlate with different cancer types and clinicopathological features. Here, we summarized the updated gastric cancer-associated miRNAs and the downstream targets in the process of tumorigenesis. Recently, many researchers make use of the miRNA microarray platform to profile miRNA expression in gastric cancer and correlated with different clinical parameters. Its application on cancer diagnosis, prognosis and predicting treatment response rate are still underway and needs further investigation. Emerging roles of miRNAs with oncogenic or tumor suppressive properties in gastric tumorigenesis were discussed. Epigenetic silencing of miRNA by hypermethylation of promoter CpG island was also observed in gastric cancer. However, detailed mechanisms of how miRNAs regulate gene expression in gastric cancer has not been well studied. In this review, we highlight the up-to-date findings on the deregulated miRNAs in gastric cancer, and the potential use of miRNA in the clinical settings, such as diagnostic/prognostic markers and chemotherapeutic tools.

MicroRNA and signaling pathways in gastric cancer

MicroRNAs (miRNAs) function as either oncogenes or tumor suppressors by inhibiting the expression of target genes, some of which are either directly or indirectly involved with canonical signaling pathways. The relationship between miRNAs and signaling pathways in gastric cancer is extremely complicated. In this paper, we determined the pathogenic mechanism of gastric cancer related to miRNA expression based on recent high-quality studies and then clarified the regulation network of miRNA expression and the correlated functions of these miRNAs during the progression of gastric cancer. We try to illustrate the correlation between the expression of miRNAs and outcomes of patients with gastric cancer. Understanding this will allow us to take a big step forward in the treatment of gastric cancer.

MiR-215/192 participates in gastric cancer progression

INTRODUCTION

Growing evidence indicates that microRNAs (miRNAs) play critical roles in cancer progression. However, the role of miR-215 or miR-192 in gastric carcinogenesis remains unclear at this point.

MATERIALS AND METHODS

Quantitative real-time PCR analysis is used to detect the expression levels of miR-215 or -192. Matrigel invasion assay is used to explore the effects of miR-215 or -192 on gastric cancer cells invasion ability. Statistical analysis is carried out by SPSS 19.0 software.

RESULTS

MiR-215/192 is significantly up-regulated in gastric cancer tissues from gastrectomy. The up-regulation of miR-215 or -192 was related with the clinical characteristics of gastric cancer, such as lymph node metastasis. Inhibition of miR-215/192 significantly suppressed gastric cancer cell invasion. Statistical analysis indicated that the expression of miR-215 or -192 may be a potential candidate biomarker for gastric cancer prognosis.

CONCLUSIONS

These data suggest that frequently up-regulated miR-215/192 in gastric cancer may participate in gastric cancer progression.

Mir-126 inhibits growth of SGC-7901 cells by synergistically targeting the oncogenes PI3KR2 and Crk, and the tumor suppressor PLK2

MicroRNA (miRNA)-126 (miR-126) was reported to be downregulated and to act as a tumor suppressor in cancers of the lung, cervix, bladder and prostate. However, the functions of miR-126 in gastric cancer appear to be diverse and are largely unknown. MiR-126 was reported to act as a tumor suppressor by targeting the Crk gene, or as an oncogene by targeting the SOX2 gene in gastric cancer. We identified that the expression of miR-126 was decreased in gastric cancer cell lines and tissues. PLK2, a tumor suppressor gene, was directly regulated by miR-126 in SGC-7901 cells. Overexpression of miR-126 not only suppressed the growth and clone formation of SGC-7901 cells, but also induced apoptosis in vitro, whereas inhibition of miR-126 slightly promoted SGC-7901 cell proliferation. The cell cycle was not affected by miR-126. Moreover, miR-126 suppressed tumor growth in vivo in a xenograft model. PLK2, PI3KR2 and Crk were regulated by miR-126 in SGC-7901 cells. We infer that the functions of miR-126 in gastric cancer depend on synergistic targeting balance between oncogenes and anti-oncogenes. Our study indicates that miR-126 is a tumor suppressor, which in the future may become a therapeutic target for gastric cancer.

Lessons from miR-143/145: the importance of cell-type localization of miRNAs

miR-143 and miR-145 are co-expressed microRNAs (miRNAs) that have been extensively studied as potential tumor suppressors. These miRNAs are highly expressed in the colon and are consistently reported as being downregulated in colorectal and other cancers. Through regulation of multiple targets, they elicit potent effects on cancer cell growth and tumorigenesis. Importantly, a recent discovery demonstrates that miR-143 and miR-145 are not expressed in colonic epithelial cells; rather, these two miRNAs are highly expressed in mesenchymal cells such as fibroblasts and smooth muscle cells. The expression patterns of miR-143 and miR-145 and other miRNAs were initially determined from tissue level data without consideration that multiple different cell types, each with their own unique miRNA expression patterns, make up each tissue. Herein, we discuss the early reports on the identification of dysregulated miR-143 and miR-145 expression in colorectal cancer and how lack of consideration of cellular composition of normal tissue led to the misconception that these miRNAs are downregulated in cancer. We evaluate mechanistic data from miR-143/145 studies in context of their cell type-restricted expression pattern and the potential of these miRNAs to be considered tumor suppressors. Further, we examine other examples of miRNAs being investigated in inappropriate cell types modulating pathways in a non-biological fashion. Our review highlights the importance of determining the cellular expression pattern of each miRNA, so that downstream studies are conducted in the appropriate cell type.

Suppressive effect of microRNA-126 on oral squamous cell carcinoma in vitro

MicroRNA-126 (miR-126), an endothelial-specific miRNA located within intron 7 of epidermal growth factor‑like domain 7 (EGFL7), has been demonstrated to act as a tumor suppressor in various types of human cancer. However, its role in oral squamous cell carcinoma (OSCC) remains unclear. In the present study, we revealed that the expression of miR-126 was significantly decreased in OSCC tissues, when compared with that in their matched adjacent tissues, and its expression level was also reduced in Tca8113, OSCC-15 and CAL27 cell lines compared with normal tissues. The protein expression of EGFL7 was upregulated in OSCC tissues compared with their matched adjacent tissues as well as normal tissues, and Tca8113, OSCC-15 and CAL27 cells additionally demonstrated a positive expression of EGFL7. The overexpression of miR-126 significantly reduced the protein expression of EGFL7 in OSCC-15 cells, while transfection with the miR-126 inhibitor upregulated the EGFL7 protein level in OSCC-15 cells. Furthermore, transfection with an miR-126 mimic into OSCC-15 cells markedly suppressed cell proliferation, cell cycle progression, cell invasion and colony formation, while inducing cell apoptosis, which contrasted with the effects of transfection with an miR-126 inhibitor. The overexpression of miR-126 suppressed the secretion of two key regulators of angiogenesis, vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF), which was also reversed by miR-126 inhibitor transfection. In conclusion, the present study demonstrated that miR-126 acts as a tumor suppressor in OSCC cells, partially at least via the downregulation of EGFL7. Thus, miR-126 may serve as a promising candidate for the treatment of OSCC.

CEACAM6 promotes tumor migration, invasion, and metastasis in gastric cancer

Carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6) shows increased expression in a wide variety of human cancers, and its over-expression is associated with enhanced migration, invasion, and in vivo metastasis. Here, we reported that CEACAM6 was up-regulated in gastric cancer (GC) cell lines and tumor tissues. Over-expression of CEACAM6 in MKN-45 and SGC-7901 GC cells promoted migration and invasion in vitro and metastasis in athymic mice, whereas migration and invasion of MKN-28 and SNU-16 GC cells were suppressed by knockdown of CEACAM6. We also observed that steroid receptor coactivator (C-SRC) phosphorylation was increased when CEACAM6 was over-expressed in SGC-7901 cells. Taken together, these results suggested that CEACAM6 functions as an oncoprotein in GC and may be an important metastatic biomarker and therapeutic target.

Oncogenic micro-RNAs and Renal Cell Carcinoma

Tumor formation is a complex process that occurs in different steps and involves many cell types, including tumor cells, endothelial cells, and inflammatory cells, which interact to promote growth of the tumor mass and metastasization. Epigenetic alterations occurring in transformed cells result in de-regulation of miRNA expression (a class of small non-coding RNA that regulates multiple functions), which contributes to tumorigenesis. The specific miRNAs, which have an aberrant expression in tumors, are defined as oncomiRNAs, and may be either over- or under-expressed, but down-regulation is most commonly observed. Renal cell carcinoma (RCC) is a frequent form of urologic tumor, associated with an alteration of multiple signaling pathways. Many molecules involved in the progression of RCCs, such as HIF, VEGF, or mammalian target of rapamycin, are possible targets of de-regulated miRNAs. Within tumor mass, the cancer stem cell (CSC) population is a fundamental component that promotes tumor growth. The CSC hypothesis postulates that CSCs have the unique ability to self-renew and to maintain tumor growth and metastasis. CSCs present in RCC were shown to express the mesenchymal stem cell marker CD105 and to exhibit self-renewal and clonogenic properties, as well as the ability to generate serially transplantable tumors. The phenotype of CSC has been related to the potential to undergo the epithelial–mesenchymal transition, which has been linked to the expression pattern of tumorigenic miRNAs or down-regulation of anti-tumor miRNAs. In addition, the pattern of circulating miRNAs may allow discrimination between healthy and tumor patients. Therefore, a miRNA signature may be used as a tumor biomarker for cancer diagnosis, as well as to classify the risk of relapse and metastasis, and for a guide for therapy.

MicroRNA-126 modulates the tumor microenvironment by targeting calmodulin-regulated spectrin-associated protein 1 (Camsap1)

Plasma miRNAs have been reported as biomarkers for various diseases. In this study, we investigated whether plasma concentrations of miR-126 may be useful as biomarkers for laryngeal squamous cell carcinoma (LSCC). We examined the function and mechanism of miR-126 in LSCC by using cell biology and molecular pathology techniques such as western blotting, quantitative PCR, IHC and IF. The expression of Camsap1 mRNA and protein is higher in cancer tissues compared to that in normal tissues. Both miR-126 and Camsap1 were related with the prognosis of LSCC patients. We found that miR-126 was able to inhibit LSCC partly by suppressing Camsap1 expression. In addition, Camsap1 expression induced microtubule formation and aggregation. This mechanism possibly explains why loss of miR-126 is frequently associated with tumor metastasis.