The quantitative analysis by stem-loop real-time PCR revealed the microRNA-34a, microRNA-155 and microRNA-200c overexpression in human colorectal cancer

Identification of miRNAs Present in Cell- and Plasma-Derived Extracellular Vesicles-Possible Biomarkers of Colorectal Cancer

Globally, an increasing prevalence of colorectal cancer (CRC) prompts a need for the development of new methods for early tumor detection. MicroRNAs (also referred to as miRNAs) are short non-coding RNA molecules that play a pivotal role in the regulation of gene expression. MiRNAs are effectively transferred to extracellular vesicle (EVs) membrane sacs commonly released by cells. Our study aimed to examine the expression of miRNAs in four CRC cell lines and EVs derived from them (tumor EVs) in comparison to the normal colon epithelium cell line and its EVs. EVs were isolated by ultracentrifugation from the culture supernatant of SW480, SW620, SW1116, HCT116 and normal CCD841CoN cell lines and characterized according to the MISEV2023 guidelines. MiRNAs were analyzed by small RNA sequencing and validated by quantitative PCR. The performed analysis revealed 22 common miRNAs highly expressed in CRC cell lines and effectively transferred to tumor EVs, including miR-9-5p, miR-182-5p, miR-196b-5p, miR-200b-5p, miR-200c-3p, miR-425-5p and miR-429, which are associated with development, proliferation, invasion and migration of colorectal cancer cells, as well as in vesicle maturation and transport-associated pathways. In parallel, normal cells expressed miRNAs, such as miR-369 and miR-143, which play a role in proinflammatory response and tumor suppression. The analysis of selected miRNAs in plasma-derived EVs and tumor samples from CRC patients showed the similarity of miRNA expression profile between the patients' samples and CRC cell lines. Moreover, miR-182-5p, miR-196-5p, miR-425-5p and miR-429 were detected in several EV samples isolated from patients' plasma. Our results suggest that miR-182-5p, miR-196b-5p and miR-429 are differentially expressed between EVs from CRC patients and healthy donors, which might have clinical implications.

Effect of miR-34a on the expression of clock and clock-controlled genes in DLD1 and Lovo human cancer cells with different backgrounds with respect to p53 functionality and 17β-estradiol-mediated regulation

The small non-coding RNA miR-34a is a p53-regulated miRNA that acts as a tumour suppressor of colorectal cancer (CRC). Oncogenesis is also negatively influenced by deregulation of the circadian system in many types of tumours with various genetic backgrounds. As the clock gene per2 was recently recognized as one of the target genes of miR-34a, we focused on the miR-34a-mediated influence on the circadian oscillator in CRC cell lines DLD1 and LoVo, which differ in their p53 status. Previously, a sex-dependent association between the expression of per2 and that of miR-34a was demonstrated in CRC patients. Therefore, we also investigated the effect of 17β-estradiol (E2) on miR-34a oncostatic functions. miR-34a mimic caused a pronounced inhibition of per2 expression in both cell lines. Moreover, miR-34a mimic significantly inhibited bmal1 expression in LoVo and rev-erbα expression in DLD1 cells and induced clock gene expression in both cell lines. miR-34a mimic caused a pronounced decrease in sirt1 and cyclin D1 expression, which may be related to the inhibition of proliferation observed after mir-34a administration in DLD1 cells. E2 administration inhibited the migration and proliferation of DLD1 cells. E2 and miR-34a, when administered simultaneously, did not potentiate each other's effects. To conclude, miR-34a strongly influences the expression of components of the circadian oscillator without respect to p53 status and exerts its oncostatic effects via inhibition of sirt1 and cyclin D1 mRNA expression. E2 administration inhibits the growth of DLD1 cells; however, this effect seems to be independent of miR-34a-mediated action. With respect to the possible use of miR-34a in cancer treatment, clock genes can be considered as off-target genes, as changes in their expression induced by miR-34a treatment do not contribute to the oncostatic functions of miR-34a. Possible ambiguous oncogenic characteristics should be taken into consideration in future clinical studies focused on miR-34a.

HypoxaMIRs: Key Regulators of Hallmarks of Colorectal Cancer

Hypoxia in cancer is a thoroughly studied phenomenon, and the logical cause of the reduction in oxygen tension is tumor growth itself. While sustained hypoxia leads to death by necrosis in cells, there is an exquisitely regulated mechanism that rescues hypoxic cells from their fatal fate. The accumulation in the cytoplasm of the transcription factor HIF-1α, which, under normoxic conditions, is marked for degradation by a group of oxygen-sensing proteins known as prolyl hydroxylases (PHDs) in association with the von Hippel-Lindau anti-oncogene (VHL) is critical for the cell, as it regulates different mechanisms through the genes it induces. A group of microRNAs whose expression is regulated by HIF, collectively called hypoxaMIRs, have been recognized. In this review, we deal with the hypoxaMIRs that have been shown to be expressed in colorectal cancer. Subsequently, using data mining, we analyze a panel of hypoxaMIRs expressed in both normal and tumor tissues obtained from TCGA. Finally, we assess the impact of these hypoxaMIRs on cancer hallmarks through their target genes.

Long transcripts minus touchdown qPCR (LTMT-qPCR): a simplified and convenient method for the screening and quantification of microRNA profiles

Due to the short length and differences in abundance of microRNAs, microRNA profile screening and quantification is challenging. In this study, we found that size selection magnetic beads could be employed to easily and efficiently remove long RNA transcripts. After removing the long transcripts, the remaining small RNAs could be concentrated and then reverse-transcribed using universal stem-loop primers (USLP), with six randomized nucleotides at the 3' end region. The efficiency of reverse transcription decreased when the number of randomized nucleotides was reduced. In addition, we found that touchdown qPCR improved microRNA profile detection, with lower C_T values and better detection efficiency than the regular qPCR protocol, especially for those low-abundance microRNAs. Finally, we incorporated these observations to create a new protocol we named long transcripts minus touchdown qPCR (LTMT-qPCR). We performed a side-by-side comparison of LTMT with USLP and traditional stem-loop primer (TSLP) protocols. We found that LTMT has higher detection efficiency than USLP, especially for the detection of low-abundance microRNAs. Although LTMT was equivalent to TSLP in terms of microRNA profile detection, LTMT is more convenient, user-friendly, and cost-effective. Taken together, the present data indicate that LTMT is a simple, rapid, and user-friendly approach that has higher precision, accuracy, and sensitivity than the previously described methods, making it more suitable for microRNA profile screening and quantification.

The miR-200 Family of microRNAs: Fine Tuners of Epithelial-Mesenchymal Transition and Circulating Cancer Biomarkers

The miR-200 family of microRNAs (miRNAs) includes miR-200a, miR-200b, miR-200c, miR-141 and miR-429, five evolutionarily conserved miRNAs that are encoded in two clusters of hairpin precursors located on human chromosome 1 (miR-200b, miR-200a and miR-429) and chromosome 12 (miR-200c and miR-141). The mature -3p products of the precursors are abundantly expressed in epithelial cells, where they contribute to maintaining the epithelial phenotype by repressing expression of factors that favor the process of epithelial-to-mesenchymal transition (EMT), a key hallmark of oncogenic transformation. Extensive studies of the expression and interactions of these miRNAs with cell signaling pathways indicate that they can exert both tumor suppressor- and pro-metastatic functions, and may serve as biomarkers of epithelial cancers. This review provides a summary of the role of miR-200 family members in EMT, factors that regulate their expression, and important targets for miR-200-mediated repression that are involved in EMT. The second part of the review discusses the potential utility of circulating miR-200 family members as diagnostic/prognostic biomarkers for breast, colorectal, lung, ovarian, prostate and bladder cancers.

Evaluation and Predictive Factors of Complete Response in Rectal Cancer after Neoadjuvant Chemoradiation Therapy

The response to neoadjuvant chemoradiation therapy is an important prognostic factor for locally advanced rectal cancer. Although the majority of the patients after neoadjuvant therapy are referred to following surgery, the clinical data show that complete clinical or pathological response is found in a significant proportion of the patients. Diagnostic accuracy of confirming the complete response has a crucial role in further management of a rectal cancer patient. As the rate of clinical complete response, unfortunately, is not always consistent with pathological complete response, accurate diagnostic parameters and predictive markers of tumor response may help to guide more personalized treatment strategies and identify potential candidates for nonoperative management more safely. The management of complete response demands interdisciplinary collaboration including oncologists, radiotherapists, radiologists, pathologists, endoscopists and surgeons, because the absence of a multidisciplinary approach may compromise the oncological outcome. Prediction and improvement of rectal cancer response to neoadjuvant therapy is still an active and challenging field of further research. This literature review is summarizing the main, currently known clinical information about the complete response that could be useful in case if encountering such condition in rectal cancer patients after neoadjuvant chemoradiation therapy, using as a source PubMed publications from 2010–2021 matching the search terms “rectal cancer”, “neoadjuvant therapy” and “response”.

MiR-200c promotes papillary thyroid cancer cell proliferation, migration, and invasion by downregulating PTEN

MiR-200c has been reported in several types of human cancer. Nevertheless, the expression profile and biological functions of miR-200c remain uncovered papillary thyroid cancer (PTC). The expression level of miR-200c was evaluated in PTC tissues using RT-qPCR. Survival analysis was performed in a cohort of 88 PTC patients. The effects of miR-200c on cell proliferation, migration, and invasion capacities were analyzed using CCK-8 and transwell assays. Target genes of miR-200c were assessed using luciferase reporter assay, RT-qPCR, Western blot and rescue experiments. MiR-200c was found to be upregulated in human PTC tissues and closely associated with pN stage and distant metastasis. High expression of miR-200c was associated with poor clinical prognosis in PTC patients. Whilst overexpression of miR-200c was demonstrated to promote the proliferation, migration, and invasion of PTC cells; knockdown of miR-200c showed an opposite inhibitory effect. Bioinformatics analysis and luciferase reporter assays confirmed that PTEN is a downstream target of miR-200c. Functional assays demonstrated that PTC cell proliferation, migration, and invasion were promoted by miR-200c via negative regulation of PTEN. Finally, overexpression of PTEN was shown to partially reverse the tumor promoting effect of miR-200c. In conclusion, this study indicates that miR-200c is a crucial prognostic biomarker of PTC, and that targeting of miR-200c/ PTEN axis may be of therapeutic significance in PTC patients.

Prognostic value of low microRNA-34a expression in human gastrointestinal cancer: a systematic review and meta-analysis

Background

Mounting evidence shows that microRNA-34a (miR-34a) is involved in cancer prognosis. Therefore, we summarize the predictive role of miR-34a for survival in patients with gastrointestinal cancers (GICs).

Methods

All eligible studies were found by searching PubMed, Web of Science and EMBASE, and survival results were extracted. Then, the hazard ratio (HR) with the corresponding 95% confidence interval (CI) was calculated to evaluate the prognostic role of miR-34a in GICs. The association between miR-34a expression and clinicopathological characteristics was estimated by odds ratios (ORs) and 95% CIs.

Results

A total of 20 studies were included in this meta-analysis. For overall survival (OS), lower miR-34a expression could probably predict poorer outcome in GICs, with a pooled HR of 1.86 (95% CI: 1.52–2.28, P < 0.01). For disease-free survival (DFS), progression-free survival (PFS), and recurrence-free survival (RFS), lower miR-34a expression was related to worse DFS/PFS/RFS with a pooled HR of 1.86 (95% CI: 1.31–2.63, P  <  0.01). A significant relation of differentiation/TNM stage/lymphatic metastasis and the expression level of miR-34a was identified.

Conclusion

This meta-analysis revealed that lower miR-34a expression is significantly connected with worse OS and DFS/PFS/RFS in GIC patients. In addition, the miR-34a expression level is relatively lower in patients with lymph node metastasis than in patients without lymph node metastasis, and decreased miR-34a expression levels are linked to poor tumour differentiation and late TNM stage. MiR-34a may become a new factor for the prognosis prediction and progression of GICs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-020-07751-y.

MicroRNA: Another Pharmacological Avenue for Colorectal Cancer?

MicroRNAs (miR) are single-stranded RNA of 21-23 nucleotides in length that repress mRNA translation and induces mRNA degradation. miR acts as an endogenous factor of gene expression and plays a crucial part in cancer biology such as cell development, proliferation, differentiation, and apoptosis. Numerous research has indicated that dysregulation of miR associates with colorectal carcinogenesis. In this review article, we firstly introduce the background of miR and colorectal cancer, and the mechanisms of miR in colorectal cancer, such as the proliferation, apoptosis, and progression. Then, we summarize the theranostic value of miR in colorectal cancer. Eventually, we discuss the potential directions and perspectives of miR. This article serves as a guide for further studies and implicate miR as a potent theranostic target for colorectal cancer.

Identification of MicroRNA-Target Gene-Transcription Factor Regulatory Networks in Colorectal Adenoma Using Microarray Expression Data

Objective

The aim of the study was to find the key genes, microRNAs (miRNAs) and transcription factors (TFs) and construct miRNA-target gene-TF regulatory networks to investigate the underlying molecular mechanism in colorectal adenoma (CRA).

Methods

Four mRNA expression datasets and one miRNA expression dataset were downloaded from Gene Expression Omnibus (GEO) database. Differentially expressed miRNAs (DEMs) and differentially expressed genes (DEGs) were identified between CRA and normal samples. Moreover, functional enrichment analysis for DEGs was carried out utilizing the Cytoscape-plugin, known as ClueGO. These DEGs were mapped to STRING database to construct a protein-protein interaction (PPI) network. Then, a miRNA-target gene regulatory network was established to screen key DEMs. In addition, similar workflow of the analyses were also performed comparing the CRC samples with CRA ones to screen key DEMs. Finally, miRNA-target gene-TF regulatory networks were constructed for these key DEMs using iRegulon plug-in in Cytoscape.

Results

We identified 514 DEGs and 167 DEMs in CRA samples compared to healthy samples. Functional enrichment analysis revealed that these DEGs were significantly enriched in several terms and pathways, such as regulation of cell migration and bile secretion pathway. A PPI network was constructed including 325 nodes as well as 890 edges. A total of 59 DEGs and 65 DEMs were identified in CRC samples compared to CRA ones. In addition, Two key DEMs in CRA samples compared to healthy samples were identified, such as hsa-miR-34a and hsa-miR-96. One key DEM, hsa-miR-29c, which was identified when we compared the differentially expressed molecules found in the comparison CRA versus normal samples to the ones obtained in the comparison CRC versus CRA, was also identified in CRC samples compared to CRA ones. The miRNA-target gene-TF regulatory networks for these key miRNAs included two TFs, one TF and five TFs, respectively.

Conclusion

These identified key genes, miRNA, TFs and miRNA-target gene-TF regulatory networks associated with CRA, to a certain degree, may provide some hints to enable us to better understand the underlying pathogenesis of CRA.

A Systemic Review on the Regulatory Roles of miR-34a in Gastrointestinal Cancer

MicroRNAs (miRNAs) are a class of endogenous non-coding single-stranded small-molecule RNAs that regulate gene expression by repressing target messenger RNA (mRNA) translation or degrading mRNA. miR-34a is one of the most important miRNAs participating in various physiological and pathological processes. miR-34a is abnormally expressed in a variety of tumors. The roles of miR-34a in gastrointestinal cancer (GIC) draw lots of attention. Numerous studies have demonstrated that dysregulated miR-34a is closely related to the proliferation, differentiation, migration, and invasion of tumor cells, as well as the diagnosis, prognosis, treatment, and chemo-resistance of tumors. Thus, we systematically reviewed the abnormal expression and regulatory roles of miR-34a in GICs including esophageal cancer (EC), gastric cancer (GC), colorectal cancer (CRC), hepatocellular carcinoma (HCC), pancreatic cancer (PC), and gallbladder cancer (GBC). It may provide a profile of versatile roles of miR-34a in GICs.

Epigenetics of colorectal cancer: biomarker and therapeutic potential

Colorectal cancer (CRC), a leading cause of cancer-related death worldwide, evolves as a result of the stepwise accumulation of a series of genetic and epigenetic alterations in the normal colonic epithelium, leading to the development of colorectal adenomas and invasive adenocarcinomas. Although genetic alterations have a major role in a subset of CRCs, the pathophysiological contribution of epigenetic aberrations in this malignancy has attracted considerable attention. Data from the past couple of decades has unequivocally illustrated that epigenetic marks are important molecular hallmarks of cancer, as they occur very early in disease pathogenesis, involve virtually all key cancer-associated pathways and, most importantly, can be exploited as clinically relevant disease biomarkers for diagnosis, prognostication and prediction of treatment response. In this Review, we summarize the current knowledge on the best-studied epigenetic modifications in CRC, including DNA methylation and histone modifications, as well as the role of non-coding RNAs as epigenetic regulators. We focus on the emerging potential for the bench-to-bedside translation of some of these epigenetic alterations into clinical practice and discuss the burgeoning evidence supporting the potential of emerging epigenetic therapies in CRC as we usher in the era of precision medicine.

Molecular expression profiles of selected microRNAs in colorectal adenocarcinoma in patients from south-eastern part of Romania

MicroRNAs (miRNAs) are endogenous, non-coding class of RNAs with functions in the regulation of genes expressions. Dysregulated expressions of miRNAs play important roles in carcinogenesis and cancer progression by targeting various oncogenes and tumor-suppressor genes. miRNAs represent a new field for molecular diagnosis and prognosis of colorectal cancer (CRC) due to their high tissue specificity, their stability, and their dysregulated expression in tumor development.This study aimed to investigate using the qRT-PCR method the expression profile and prognostic value of 11 mature miRNAs in a cohort of 82 Romanian patients diagnosed with CRC. The relationship between the expression levels of selected miRNAs and clinicopathologic features were evaluated using ANOVA and Pearson test. In addition, the receiver operating characteristic (ROC) and area under the curve (AUC) were used to assess the diagnostic values of the miRNAs to discriminate cancerous from non-cancerous states of the samples.The expression levels of miR-30c, miR-144, miR-375, miR-214, and miR-195 in CRC tissue were significantly downregulated (all P < .05; Paired T-Test) than that in normal adjacent tissue sample (NATS), while the expression of miR-141, miR-182, miR-183, miR-21, and miR-370 in CRC tissue were significantly upregulated (all P < .001) than that in NATS. Moreover, the expression levels of miR-182, miR-183, miR-141, and miR-21 were demonstrated to be associated with a gradual increase in fold change expression with depth of tumor invasion (all P < .05), lymph node invasion (all P < .001), and maximal increase with distant metastasis (all P < .001). Moreover, the analysis of ROC curves revealed that AUC (95% CI) of miR-182, miR-183, miR-141, and miR-21 in diagnosis of CRC was 0.76 (0.66-0.87), 0.85 (0.78-0.94), 0.77 (0.62-0.92), 0.83 (0.73-0.90), respectively. The univariate and multivariate Cox-proportional hazard regression for all variables revealed that the nodal status, distant metastasis, miR-21, miR-141, miR-182, and miR-183 were independent prognostic markers of CRC.In conclusion, altered expressions of miR-21, miR-141, miR-182, and miR-183 in CRC varies at different stages of CRC development and may serve as potential diagnosis molecular biomarkers in Romanian patients with CRC. Further investigations are needed to confirm our findings.

miR-34b Alleviates High Glucose-Induced Inflammation and Apoptosis in Human HK-2 Cells via IL-6R/JAK2/STAT3 Signaling Pathway

Background

It is well established that inflammation and apoptosis of renal tubular epithelial cells caused by hyperglycemia contribute to the development of diabetic nephropathy (DN). Although microRNAs (miRNAs) are known to have roles in inflammation-related disorders, the exact role of miR-34b in DN has not been defined, and the regulatory mechanism has been unclear. This study aimed to clarify the role of miR-34b in DN pathogenesis.

Material/Methods

Expression of miR-34b, IL-6R, and other key factors of inflammation, apoptosis (TNF-α, IL-1β, IL-6, caspase-3) in high glucose (HG)-induced HK-2 cells were measured by real-time PCR, Western blot, and flow cytometric cell apoptosis assays. We used luciferase reporter assay to detect the target of miR-34b. Moreover, the targeting gene of miR-34b and its downstream JAK2/STAT3 signaling pathway were explored.

Results

It was demonstrated that miR-34b overexpression inhibited apoptosis and expression levels of TNF-α, IL-1β, IL-6, and caspase-3 in HG-treated HK-2 cells. We also found that IL-6R is a direct target of miR-34b, which could rescue inflammation and apoptosis in HG-treated HK-2 cells transfected with miR-34b mimic. Furthermore, we showed that overexpression of miR-34b inhibited the IL-6R/JAK2/STAT3 signaling pathway in HG-treated HK-2 cells.

Conclusions

Our data suggest that overexpression of miR-34b improves inflammation and ameliorates apoptosis in HG-induced HK-2 cells via the IL-6R/JAK2/STAT3 pathway, indicating that miR-34b could be a promising therapeutic target in DN.

Expression of miR-34a-5p is up-regulated in human colorectal cancer and correlates with survival and clock gene PER2 expression

Colorectal cancer represents a leading cause of cancer death. MicroRNAs (miRNAs) are small non-coding RNA molecules that have been extensively studied in tumours, since changes in their levels can reveal patient prognosis. Cancer progression is also influenced by the circadian system whose functioning is based on the rhythmic expression of clock genes. Therefore, we performed macroarray screening of tumour and adjacent tissues in patients undergoing surgery for colorectal carcinoma. We identified 17 miRNAs showing expression that was more than 100 times higher in tumour tissue compared to adjacent tissue. From in silico analysis, miR-34a-5p was selected as showing a computer-predicted interaction with PER2. Real-time PCR revealed a negative correlation between expression of PER2 mRNA and miR-34a in patients with more advanced cancer stage. Expression of miR-34a was up-regulated in cancer tissue compared to adjacent tissue. High miR-34a expression was associated with better survival of patients. miR-34a showed lower expression levels in male patients with lymph node involvement, and a trend towards decreased expression in male patients with distant metastases. Male patients, but not female patients, with high expression of miR-34a and who were free of distant metastases and/or lymph node involvement showed better survival. Therefore, we proposed that expression of miR-34a was regulated in a sex-dependent manner and could be considered a marker of prognosis in earlier cancer stages in male patients.

Epithelial-Mesenchymal Transition-Related MicroRNAs and Their Target Genes in Colorectal Cancerogenesis

MicroRNAs of the miR-200 family have been shown experimentally to regulate epithelial-mesenchymal transition (EMT). Although EMT is the postulated mechanism of development and progression of colorectal cancer (CRC), there are still limited and controversial data on expression of miR-200 family and their target genes during CRC cancerogenesis. Our study included formalin-fixed paraffin-embedded biopsy samples of 40 patients (10 adenomas and 30 cases of CRC with corresponding normal mucosa). Expression of miR-141, miR-200a/b/c and miR-429 and their target genes (CDKN1B, ONECUT2, PTPN13, RND3, SOX2, TGFB2 and ZEB2) was analysed using quantitative real-time PCR. Expression of E-cadherin was analysed using immunohistochemistry. All miRNAs were down-regulated and their target genes showed the opposite expression in CRC compared to adenoma. Down-regulation of the miR-200 family at the invasive front in comparison to the central part of tumour was observed as well as a correlation of expression of miR-200b, CDKN1B, ONECUT2 and ZEB2 expression to nodal metastases. Expression of the miR-200 family and SOX2 also correlated with E-cadherin staining. These results suggest that the miR-200 family and their target genes contribute to progression of adenoma to CRC, invasive properties and development of metastases. Our results strongly support the postulated hypotheses of partial EMT and intra-tumour heterogeneity during CRC cancerogenesis.

MicroRNA-34 family: a potential tumor suppressor and therapeutic candidate in cancer

MicroRNA-34 (miR-34) has been reported to be dysregulated in various human cancers and regarded as a tumor suppressive microRNA because of its synergistic effect with the well-known tumor suppressor p53. Along with the application of MRX34, the first tumor-targeted microRNA drug which based on miR-34a mimics, on phase I clinical trial (NCT01829971), the significance of miR-34 is increasingly recognized. miR-34 plays a crucial role on repressing tumor progression by involving in epithelial-mesenchymal transition (EMT) via EMT- transcription factors, p53 and some important signal pathways. Not only that, numerous preclinical researches revealed the giant potential of miR-34a on cancer therapy through diversiform nano-scaled delivery systems. Here, we provide an overview about the function of miR-34 in various cancers and the mechanism of miR-34 in tumor-associated EMT. Furthermore, its potential role as a microRNA therapeutic candidate is also discussed. Notwithstanding some obstacles existed, the extensive application prospect of miR-34 on oncotherapy cannot be neglected.

One step ahead: miRNA-34 in colon cancer-future diagnostic and therapeutic tool?

The discovery that microRNAs (miRNAs) - short, non-coding RNA molecules which regulate gene expression - are implicated in many types of cancer has revolutionised cancer research, giving hope for a new perspective in diagnostics and treatment. Dysregulation of miRNAs occurs in various malignancies, including colorectal cancer (CRC). CRC is one of the leading causes of cancer-related death and in most countries its incidence is still rising. Among several miRNAs which have been linked to CRC, miR-34 has attracted particular attention. This miRNA is involved in the regulation of cell cycle and apoptosis through multiple signaling pathways such as p53, Ra and Wnt signaling. Understanding its role in CRC may facilitate its future use as a diagnostic tool and therapeutic target.

KIF14 promotes cell proliferation via activation of Akt and is directly targeted by miR-200c in colorectal cancer

As a mitotic kinesin, kinesin family member 14 (KIF14) has been reported to serve oncogenic roles in a variety of malignancies; however, its functional role and regulatory mechanisms in colorectal cancer (CRC) remain unclear. In the present study, KIF14 was observed to be markedly overexpressed in CRC, and this upregulation was associated with tumor size and marker of proliferation Ki-67 immunostaining scores. Gain- and loss-of-function experiments were applied to identify the function of KIF14 in CRC progression. In vitro and in vivo assays revealed that KIF14 promoted CRC cell proliferation and accelerated the cell cycle via activation of protein kinase B. In addition, the present study investigated the potential mechanisms underlying KIF14 overexpression in CRC. Bioinformatics analyses and validation experiments, including reverse transcription-quantitative polymerase chain reaction, western blotting and a Dual-Luciferase reporter assay, demonstrated that, in addition to genomic amplification and transcriptional activation, KIF14 was regulated by microRNA (miR)-200c at the post-transcriptional level. Rescue experiments further demonstrated that decreased miR-200c expression could facilitate KIF14 to exert its pro-proliferative role. The expression of miR-200c was negatively correlated with KIF14 in CRC specimens. Collectively, the findings of the present study demonstrated the oncogenic role of KIF14 in colorectal tumorigenesis, and also revealed a complexity of regulatory mechanisms mediating KIF14 overexpression, which may provide insight for developing novel treatments for patients with CRC.

Expression of miR-200c and its clinicopathological significance in patients with colorectal cancer

MicroRNA-200c (miR-200c) is known to play a pivotal role in the regulation of epithelial-to-mesenchymal and mesenchymal-to-epithelial transition processes. However, the biological function of miR-200c in human carcinogenesis remains controversial. We examined the association of miR-200c expression with various clinicopathological factors, including KRAS mutation status and survival, in patients with colorectal cancer (CRC). The expression level of miR-200c was evaluated in 109 paired CRC and normal tissue samples using quantitative reverse transcription polymerase chain reaction. The KRAS mutation status of the CRC samples was determined using the PNAClamp™ KRAS Mutation Detection kit. Compared with the normal tissue group, miR-200c expression was significantly upregulated in the CRCs (P < .001). The expression of miR-200c was increased in CRCs with higher grade (P = .009), advanced stage (P = .042), and lymphovascular invasion (P = .003). Thirty-one CRCs (28.4%) had KRAS mutations in codon 12 or 13. CRCs with KRAS mutations had significantly higher miR-200c expression than CRCs with wild-type KRAS (P = .003). In survival analysis, high miR-200c expression was correlated with worse overall survival (P = .017) and recurrence-free survival (P = .048). Our results indicate that miR-200c is involved in tumor progression and aggressiveness in CRCs, and this oncogenic role of miR-200c may be triggered by activation of the KRAS signaling pathway.

MicroRNA-155 increases colon cancer chemoresistance to cisplatin by targeting forkhead box O3

To investigate the effect of microRNA (miR)-155 on colon cancer chemoresistance to cisplatine and its mechanism. Reverse transcription quantitative polymerase chain reaction was used to measure the levels of miR-155 and forkhead box O3 (FOXO3) in colon cancer specimens and cell lines. Overexpression of miR-155 and miR-155 inhibitor were transfected into colon cancer cell lines to investigate its role of chemoresistance to cisplatin in colon cancer. MTS assays were used to analyse cell viability in vitro. In vivo tumor formation assays were performed in C57BL/6 wild type and miR-155 knockout mice (miR-155-/-). A luciferase reporter assay was used to measure the translation of FOXO3. Additionally, the expression of FOXO3 was detected by western blot analysis. It was identified that miR-155 was markedly upregulated in colon cancer tissue and cell lines. Overexpression of miR-155 enhanced colon cancer cell chemoresistance to cisplatin in vitro and tumorigenesis in vivo. In addition, overexpression of miR-155 was associated with decreased levels of FOXO3, primarily through inhibiting the expression of FOXO3 to increase colon cancer resistanec to cisplatin. The present study demonstrated that miR-155 increased colon cancer drug resistance and decreased FOXO3 expression in vivo and in vitro. This may provide a novel method for the treatment of drug-resistant colon cancer.

MicroRNA-34a: A Versatile Regulator of Myriads of Targets in Different Cancers

MicroRNA-34a (miR-34a) is a tumor suppressor that has attracted considerable attention in recent years. It modulates cancer cell invasion, metastasis, and drug resistance, and has also been evaluated as a diagnostic and/or prognostic biomarker. A number of targets of miR-34a have been identified, including some other non-coding RNAs, and it is believed that the modulation of these myriads of targets underlines the versatile role of miR-34a in cancer progression and pathogenesis. Seemingly appealing results from preclinical studies have advocated the testing of miR-34a in clinical trials. However, the results obtained are not very encouraging and there is a need to re-interpret how miR-34a behaves in a context dependent manner in different cancers. In this review, we have attempted to summarize the most recent evidence related to the regulation of different genes and non-coding RNAs by miR-34a and the advances in the field of nanotechnology for the targeted delivery of miR-34a-based therapeutics and mimics. With the emergence of data that contradicts miR-34a’s tumor suppressive function, it is important to understand miR-34a’s precise functioning, with the aim to establish its role in personalized medicine and to apply this knowledge for the identification of individual patients that are likely to benefit from miR-34a-based therapy.

Non-coding RNAs Enabling Prognostic Stratification and Prediction of Therapeutic Response in Colorectal Cancer Patients

Colorectal cancer (CRC) is a heterogeneous disease and current treatment options for patients are associated with a wide range of outcomes and tumor responses. Although the traditional TNM staging system continues to serve as a crucial tool for estimating CRC prognosis and for stratification of treatment choices and long-term survival, it remains limited as it relies on macroscopic features and cases of surgical resection, fails to incorporate new molecular data and information, and cannot perfectly predict the variety of outcomes and responses to treatment associated with tumors of the same stage. Although additional histopathologic features have recently been applied in order to better classify individual tumors, the future might incorporate the use of novel molecular and genetic markers in order to maximize therapeutic outcome and to provide accurate prognosis. Such novel biomarkers, in addition to individual patient tumor phenotyping and other validated genetic markers, could facilitate the prediction of risk of progression in CRC patients and help assess overall survival. Recent findings point to the emerging role of non-protein-coding regions of the genome in their contribution to the progression of cancer and tumor formation. Two major subclasses of non-coding RNAs (ncRNAs), microRNAs and long non-coding RNAs, are often dysregulated in CRC and have demonstrated their diagnostic and prognostic potential as biomarkers. These ncRNAs are promising molecular classifiers and could assist in the stratification of patients into appropriate risk groups to guide therapeutic decisions and their expression patterns could help determine prognosis and predict therapeutic options in CRC.

miR-34a overexpression predicts poor prognostic outcome in colorectal adenocarcinoma, independently of clinicopathological factors with established prognostic value

OBJECTIVES

MicroRNA-34a (miR-34a) is regulated by TP53 and, in response, downregulates the expression of a gamut of protein-coding genes, including apoptosis regulators, transcription factors, cyclins, and cyclin-dependent kinases. Its upregulation initiates a reprogramming of gene expression and promotes apoptosis. The purpose of this study was the investigation of the potential clinical significance of miR-34a as a molecular prognostic biomarker in colorectal adenocarcinoma using an in-house real-time quantitative PCR (qPCR) methodology.

DESIGN AND METHODS

Total RNA was extracted from 113 primary colorectal adenocarcinoma specimens and 61 paired non-cancerous colorectal tissue samples. After polyadenylation and reverse transcription, miR-34a molecules were determined using qPCR based on SYBR Green chemistry. Calculations were performed using the comparative C_T method. Finally, extensive biostatistical analysis was performed.

RESULTS

miR-34a expression does not significantly differ between colorectal adenocarcinoma tissue specimens and adjacent non-cancerous mucosae. However, miR-34a expression increases progressively as colorectal adenocarcinoma loses its differentiation, being highest in grade III tumors (P=0.010). Moreover, miR-34a expression is a potential unfavorable prognostic biomarker in colorectal adenocarcinoma, predicting poor disease-free and overall survival (P=0.002 and P=0.019, respectively), independently of classical clinicopathological parameters. Most importantly, miR-34a expression stratifies patients without local (N0) and/or distant metastasis (M0) at the time of diagnosis into two groups with substantially different prognosis (P=0.013 and P=0.002, respectively).

CONCLUSIONS

High miR-34a levels in colorectal adenocarcinoma predict a rather increased risk for disease recurrence and poor overall survival, particularly in patients at an early TNM stage. The unfavorable prognostic potential of miR-34a expression is independent of established prognostic features of colorectal adenocarcinoma.

miRNA-200c and miRNA-141 as potential prognostic biomarkers and regulators of epithelial-mesenchymal transition in eyelid sebaceous gland carcinoma

BACKGROUND

MicroRNA (miRNA)-200c and miRNA-141 are tumour suppressors, which regulate epithelial-mesenchymal transition (EMT), leading to tumour invasion and metastasis in various malignancies. miRNA-200c and miRNA-141 maintain the epithelial phenotype by post-transcriptionally inhibiting the E-cadherin repressors, zinc finger E-box binding homeobox (ZEB)1 and ZEB2. The present study was performed to determine the prognostic significance of miRNA-200c and miRNA-141, and their association with EMT markers ZEB1, ZEB2 and E-cadherin in eyelid sebaceous gland carcinoma (SGC).

METHODS

Expression levels of miRNA-200c and miRNA-141 were determined in 42 eyelid SGC cases by quantitative real-time PCR (qPCR). Their association with ZEB1, ZEB2 and E-cadherin was determined by qPCR and immunohistochemistry. Kaplan-Meier plots and Spearman's rank correlation tests were applied to analyse the data. Patients were followed up for 7-44 months.

RESULTS

Low expression levels of miRNA-200c and miRNA-141 were seen in 36/42 (86%) and 28/42 (67%) cases, respectively. Low miRNA-200c correlated significantly with large tumour size (p=0.03) and poor differentiation (p=0.03). Low miRNA-141 correlated significantly with large tumour size (p=0.02) and lymph node metastasis (p=0.04). Survival analysis revealed that patients with low miRNA-200c (p<0.05) and miRNA-141 expression (p=0.07) had shorter disease-free survival. There was a significant association of both miRNA-200c and miRNA-141 with E-cadherin and ZEB2 expression.

CONCLUSIONS

Low levels of miRNA-200c and miRNA-141 in patients with eyelid SGC facilitates tumour progression by promoting EMT and miRNA-200c has emerged as a novel potential predictor of survival.

MicroRNA-34a promotes genomic instability by a broad suppression of genome maintenance mechanisms downstream of the oncogene KSHV-vGPCR

The Kaposi's sarcoma-associated herpesvirus (KSHV)-encoded chemokine receptor vGPCR acts as an oncogene in Kaposi's sarcomagenesis. Until now, the molecular mechanisms by which the vGPCR contributes to tumor development remain incompletely understood. Here, we show that the KSHV-vGPCR contributes to tumor progression through microRNA (miR)-34a-mediated induction of genomic instability. Large-scale analyses on the DNA, gene and protein level of cell lines derived from a mouse model of vGPCR-driven tumorigenesis revealed that a vGPCR–induced upregulation of miR-34a resulted in a broad suppression of genome maintenance genes. A knockdown of either the vGPCR or miR-34a largely restored the expression of these genes and confirmed miR-34a as a downstream effector of the KSHV-vGPCR that compromises genome maintenance mechanisms. This novel, protumorigenic role of miR-34a questions the use of miR-34a mimetics in cancer therapy as they could impair genome stability.

MicroRNA in rectal cancer

In rectal cancer, one of the most common cancers worldwide, the proper staging of the disease determines the subsequent therapy. For those with locally advanced rectal cancer, a neoadjuvant chemoradiotherapy (CRT) is recommended before any surgery. However, response to CRT ranges from complete response (responders) to complete resistance (non-responders). To date we are not able to separate in advance the first group from the second, due to the absence of a valid biomarker. Therefore all patients receive the same therapy regardless of whether they reap benefits. On the other hand almost all patients receive a surgical resection after the CRT, although a watch-and-wait procedure or an endoscopic resection might be sufficient for those who responded well to the CRT. Being highly conserved regulators of gene expression, microRNAs (miRNAs) seem to be promising candidates for biomarkers. Many studies have been analyzing the miRNAs expressed in rectal cancer tissue to determine a specific miRNA profile for the ailment. Unfortunately, there is only a small overlap of identified miRNAs between different studies, posing the question as to whether different methods or differences in tissue storage may contribute to that fact or if the results simply are not reproducible, due to unknown factors with undetected influences on miRNA expression. Other studies sought to find miRNAs which correlate to clinical parameters (tumor grade, nodal stage, metastasis, survival) and therapy response. Although several miRNAs seem to have an impact on the response to CRT or might predict nodal stage, there is still only little overlap between different studies. We here aimed to summarize the current literature on rectal cancer and miRNA expression with respect to the different relevant clinical parameters.

Support Vector Machine Based on microRNA Expression Profiles to Predict Histological Origin of Ampullary Carcinoma: Case Report of a Patient Affected From Adenocarcinoma of the Papilla of Vater With Lynch Syndrome

Adenocarcinomas of Vater's papilla (PVAC) may originate from either the pancreatic duct or the intestinal epithelium. Conflicting data have been reported about the frequency of the 2 anatomical entities and their influence on patients' prognosis. To ascertain the anatomical origin of PVAC in a family member of a Lynch syndrome kindred, we searched for microRNA (miRNA) expression profiles on resected tumor specimens. The support vector machine was trained on our previous miRNAs expression data sets of pancreatic and colorectal tissue samples and used to classify the site of origin of the tumor in our patient. The support vector machine worked by contrasting the profiles of miRNAs in patients with pancreatic ductal and colorectal cancers to that of our patient, which was finally classified as pancreatic ductal adenocarcinoma accordingly to alterations of 55 miRNAs. The PVAC might be originated from ductal epithelium rather than from the intestinal mucosa of the papilla in the case at issue. Alteration of miR-548b-3p, miR-551a, miR-21, miR-92a, miR-let-7i, and miR-181a* emerged as potentially associated with cancer genetic susceptibility in PVAC.

MicroRNA-155 deletion promotes tumorigenesis in the azoxymethane-dextran sulfate sodium model of colon cancer

Clinical studies have linked microRNA-155 (miR-155) expression in the tumor microenvironment to poor prognosis. However, whether miR-155 upregulation is predictive of a pro- or antitumorigenic response is unclear, as the limited preclinical data available remain controversial. We examined miR-155 expression in tumor tissue from colon cancer patients. Furthermore, we investigated the role of this microRNA in proliferation and apoptosis, inflammatory processes, immune cell populations, and transforming growth factor-β/SMAD signaling in a chemically induced (azoxymethane-dextran sulfate sodium) mouse model of colitis-associated colon cancer. We found a higher expression of miR-155 in the tumor region than in nontumor colon tissue of patients with colon cancer. Deletion of miR-155 in mice resulted in a greater number of polyps/adenomas, an increased symptom severity score, a higher grade of epithelial dysplasia, and a decrease in survival. Surprisingly, these findings were associated with an increase in apoptosis in the normal mucosa, but there was no change in proliferation. The protumorigenic effects of miR-155 deletion do not appear to be driven solely by dysregulation of inflammation, as both genotypes had relatively similar levels of inflammatory mediators. The enhanced tumorigenic response in miR-155(-/-) mice was associated with alterations in macrophages and neutrophils, as markers for these populations were decreased and increased, respectively. Furthermore, we demonstrated a greater activation of the transforming growth factor-β/SMAD pathway in miR-155(-/-) mice, which was correlated with the increased tumorigenesis. Given the multiple targets of miR-155, careful evaluation of its role in tumorigenesis is necessary prior to any consideration of its potential as a biomarker and/or therapeutic target in colon cancer.

miRNA-21 and miRNA-34a Are Potential Minimally Invasive Biomarkers for the Diagnosis of Pancreatic Ductal Adenocarcinoma

OBJECTIVES

Pancreatic ductal adenocarcinoma (PDAC) is one of the most deadly cancers, and its diagnosis often requires invasive procedures. Deregulated miRNA expression has been described in patients with PDAC. In this study, we analyzed the expression levels of 6 miRNAs (miR-21, -34a, -155, -196a, -200b, and -376a involved in PDAC tumorigenesis) in serum and salivary samples to assess their potential role as circulating diagnostics biomarkers.

METHODS

Serum and salivary samples were collected from patients with PDAC and healthy controls, and miRNA levels were quantified using qRT-PCR. Twenty-four patients with PDAC and 10 healthy controls were recruited.

RESULTS

A significant difference between PDAC and healthy groups was observed for the expression of miR-21 and miR-34a (P < 0.001 and P = 0.001) in serum samples. Both miRNAs accurately discriminated between the 2 groups, with an area under the curve for miR-21 and miR-34a of 0.889 (P = 0.001) and 0.865 (P = 0.002), respectively. In general, the expression of miRNAs between salivary samples did not differ.

CONCLUSIONS

Serum miR-21 and miR-34a are potentially useful diagnostic biomarkers of PDAC. In addition, our results suggest that these miRNAs are not differentially expressed in saliva, making them unsuitable for use as noninvasive biomarkers for diagnostic purposes.

MicroRNAs and Inflammation in Colorectal Cancer

Colorectal cancers (CRC) are known to be related to inflammatory conditions, and inflammatory bowel diseases increase the relative risk for developing CRC. The use of anti-inflammatory drugs prevents the development of colorectal cancer.Several molecular mediators are connecting the pathways that are involved in inflammatory conditions and in carcinogenesis. By the way these pathways are tightly interwoven, with the consequence that a deregulation at the level of any of these molecular mediators can affect the others.MiRNAs are demonstrated to be deregulated in inflammatory bowel diseases and in colorectal cancer. Moreover, they target several molecular mediators that connect inflammation to cancer, and they are thus implicated in the route from inflammation to colorectal cancer.This chapter will focus on the miRNAs that are jointly deregulated in inflammatory bowel disease and in colorectal cancer. Their role on the regulation of the molecular mediators and pathways that link inflammation to cancer will be described.

The tumor-suppressive and potential therapeutic functions of miR-34a in epithelial carcinomas

INTRODUCTION

Many RNA species have been identified as important players in the development of chronic diseases including cancer. Certain classes of regulatory RNAs such as microRNAs (miRNAs) have been investigated in such detail that bona fide tumor suppressive and oncogenic miRNAs have been identified. Because of this, there has been a major effort to therapeutically target these small RNAs. One in particular, a liposomal formulation of miR-34a (MRX34), has entered Phase I trials.

AREAS COVERED

This review aims to summarize miRNA biology, its regulation within normal versus disease states and how it can be targeted therapeutically, with a particular emphasis on miR-34a. Understanding the complexity of a single miRNA will aid in the development of future RNA-based therapeutics for a broader range of chronic diseases.

EXPERT OPINION

The potential of miRNAs to be developed into anti-cancer therapeutics has become an increasingly important area of research. miR-34a is a tumor suppressive miRNA across many tumor types through its ability to inhibit cellular proliferation, invasion and tumor sphere formation. miR-34a also shows promise within certain in vivo solid tumor models. Finally, as miR-34a moves into clinical trials it will be important to determine if it can further sensitize tumors to certain chemotherapeutic agents.

Non-coding landscapes of colorectal cancer

For two decades Vogelstein’s model has been the paradigm for describing the sequence of molecular changes within protein-coding genes that would lead to overt colorectal cancer (CRC). This model is now too simplistic in the light of recent studies, which have shown that our genome is pervasively transcribed in RNAs other than mRNAs, denominated non-coding RNAs (ncRNAs). The discovery that mutations in genes encoding these RNAs [i.e., microRNAs (miRNAs), long non-coding RNAs, and circular RNAs] are causally involved in cancer phenotypes has profoundly modified our vision of tumour molecular genetics and pathobiology. By exploiting a wide range of different mechanisms, ncRNAs control fundamental cellular processes, such as proliferation, differentiation, migration, angiogenesis and apoptosis: these data have also confirmed their role as oncogenes or tumor suppressors in cancer development and progression. The existence of a sophisticated RNA-based regulatory system, which dictates the correct functioning of protein-coding networks, has relevant biological and biomedical consequences. Different miRNAs involved in neoplastic and degenerative diseases exhibit potential predictive and prognostic properties. Furthermore, the key roles of ncRNAs make them very attractive targets for innovative therapeutic approaches. Several recent reports have shown that ncRNAs can be secreted by cells into the extracellular environment (i.e., blood and other body fluids): this suggests the existence of extracellular signalling mechanisms, which may be exploited by cells in physiology and pathology. In this review, we will summarize the most relevant issues on the involvement of cellular and extracellular ncRNAs in disease. We will then specifically describe their involvement in CRC pathobiology and their translational applications to CRC diagnosis, prognosis and therapy.

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.

Increased microRNA-34b and -34c predominantly expressed in stromal tissues is associated with poor prognosis in human colon cancer

The microRNA-34 family (miR-34a, -34b and -34c) have been reported to be tumor suppressor microRNAs (miRNAs) that are regulated by the TP53 and DNA hypermethylation. However, the expression, regulation, and prognostic value of the miR-34 family have not been systematically studied in colon cancer. To elucidate the roles of miR-34 family in colon carcinogenesis, miR-34a/b/c were measured in tumors and adjacent noncancerous tissues from 159 American and 113 Chinese colon cancer patients using quantitative RT-PCR, and we examined associations between miR-34a/b/c expression with TNM staging, cancer-specific mortality, TP53 mutation status and Affymetrix microarray data. All miR-34 family members were significantly increased in colon tumors, counter to the proposed tumor suppressor role for these miRNAs. Increased miR-34b/c were observed in more advanced tumors in two independent cohorts and increased expression of miR-34b/c was associated with poor cancer-specific mortality. While the expression of miR-34 family was not associated with TP53 mutation status, TP53 transcriptional activity was associated with miR-34a/b/c expression that is consistent with the proposed regulation of miR-34a/b/c by TP53. To examine where the miR-34 family is expressed, the expression of miR-34 family was compared between epitheliums and stromal tissues using laser microdissection technique. The expression of miR-34b/c was increased significantly in stromal tissues, especially in cancer stroma, compared with epithelial tissue. In conclusion, increased miR-34b/c predominantly expressed in stromal tissues is associated with poor prognosis in colon cancer. MiR-34 may contribute to cancer-stromal interaction associated with colon cancer progression.

An update on microRNAs as colorectal cancer biomarkers: where are we and what's next?

miRNAs are abundant classes of small, endogenous non-coding RNAs, which inhibit the expression of target gene via post-transcriptional regulation. In addition to an important functional role miRNAs play in carcinogenesis, emerging evidence has demonstrated their feasibility as robust cancer biomarkers. In particular, the recent discovery of miRNAs in the body fluids provides an attractive opportunity for the development of non-invasive biomarkers for the diagnosis, prognosis and predictive response to cancer therapy. Colorectal cancer (CRC) is one of the most common cancers worldwide, and accumulating data provides a compelling case for the potential exploitation of miRNAs as CRC-biomarkers. This review summarizes the current state of literature in the field, focusing on the clinical relevance of miRNAs as potential biomarkers for CRC treatment and discussing the forthcoming challenges to further advance this exciting field of 'academic research' into 'bedside clinical care' of patients suffering from CRC.

The analysis of microRNA-34 family expression in human cancer studies comparing cancer tissues with corresponding pericarcinous tissues

Recently many studies have focused on the microRNA-34 (miR-34) family expression in various cancers; nevertheless, the controversial results of these studies still exist in identifying miR-34 members as new biomarkers of cancers. Therefore, we carried out this comprehensive meta-analysis of published studies that compared the miR-34 family expression profiles between cancer tissues and paired neighboring noncancerous tissues to systemically evaluate the findings globally and address the inconsistencies of pertinent literatures. The data included in this article were collected from Embase, PubMed and Web of Science up to December 2013. To overcome the difficulties that many raw data were unavailable and study methods were different, a vote-counting strategy was adopted to identify consistent markers in our analysis. Ultimately, a total of 23 cancers were reported in the 61 eligible studies, of which 46 studies provided fold-change value information. In the consistently reported cancer types, non-small cell lung cancer (NSCLC), glioma and nasopharyngeal carcinoma (NPC) ranked at the top with down-regulated feature. Cervical neoplasm was consistently reported to be over-expressed in the panel of each member of miR-34s. Subgroup analysis of miR-34 family expression demonstrated that colorectal cancer (CRC), gastric cancer (GC), hepatocellular carcinoma (HCC) and prostate cancer (PCa) were most frequently reported with inconsistent regulations. Our meta-analysis showed that miR-34 family members could be expected to become potential diagnostic and prognostic biomarkers in some types of human cancers. Further well-designed and larger sample studies are surely warranted to identify the role of the miR-34 family in the occurrence and development of tumors.

miR200c attenuates P-gp-mediated MDR and metastasis by targeting JNK2/c-Jun signaling pathway in colorectal cancer

MicroRNA-200c (miR200c) recently emerged as an important regulator of tumorigenicity and cancer metastasis; however, its role in regulating multidrug resistance (MDR) remains unknown. In the current study, we found that the expression levels of miR200c in recurrent and metastatic colorectal cancers were significantly lower, whereas the JNK2 expression was higher compared with primary tumors. We showed that in MDR colorectal cancer cells, miR200c targeted the 3' untranslated region of the JNK2 gene. Overexpression of miR200c attenuated the levels of p-JNK, p-c-Jun, P-gp, and MMP-2/-9, the downstream factors of the JNK signaling pathway, resulting in increased sensitivity to chemotherapeutic drugs, which was accompanied by heightened apoptosis and decreased cell invasion and migration. Moreover, in an orthotopic MDR colorectal cancer mouse model, we demonstrated that overexpression of miR200c effectively inhibited the tumor growth and metastasis. At last, in the tumor samples from patients with locally advanced colorectal cancer with routine postsurgical chemotherapy, we observed an inverse correlation between the levels of mRNA expression of miR200c and JNK2, ABCB1, and MMP-9, thus predicting patient therapeutic outcomes. In summary, we found that miR200c negatively regulated the expression of JNK2 gene and increased the sensitivity of MDR colorectal cancer cells to chemotherapeutic drugs, via inhibiting the JNK2/p-JNK/p-c-Jun/ABCB1 signaling. Restoration of miR200c expression in MDR colorectal cancer may serve as a promising therapeutic approach in MDR-induced metastasis.

MicroRNAs in colorectal cancer as markers and targets: Recent advances

MicroRNAs are evolutionarily conserved small non-coding RNA molecules encoded by eukaryotic genomic DNA, and function in post-transcriptional regulation of gene expression via base-pairing with complementary sequences in target mRNAs, resulting in translational repression or degradation of target mRNAs. They represent one of the major types of epigenetic modification and play important roles in all aspects of cellular activities. Altered expression of microRNAs has been found in various human diseases including cancer. Many efforts have been made to discover the characteristic microRNA expression profiles, to understand the roles of aberrantly expressed microRNAs and underlying mechanisms in different cancers. With the application of DNA microarray, real-time quantitative polymerase chain reaction and other molecular biology techniques, increasing evidence has been accumulated which reveal that aberrant microRNAs can be detected not only intracellularly within the cancer cells, but also extracellularly in plasma of patients, postulating the potential of aberrant microRNAs as promising diagnostic/prognostic markers and attracting therapeutic targets. This review is intended to provide the most recent advances in microRNA studies in one of the most common cancers, colorectal cancer, especially the identification of those specifically altered microRNAs in colorectal cancer, validation for their relevance to clinical pathological parameters of patients, functional analyses and potential applications of these microRNAs.

The roles of miR-200c in colon cancer and associated molecular mechanisms

The expression of miR-200c has been widely reported to be elevated in tumor tissues and sera of patients with colorectal cancer (CRC) and has been found to correlate with poor prognosis. However, how miR-200c regulates the apoptosis, survival, invasion, metastasis, and tumor growth in colon cancer cells remains to be fully elucidated. This study seeks to further investigate the role of miR-200c in colon cancer development. The expression of miR-200c in tumor and peritumoral tissues of 101 colon cancer patients was measured by real-time PCR. miR-200c expression in HCT-116 and HT-29 colon cancer cells was silenced by adenovirus-carried expression of antisense mRNA against miR-200c. The protein levels of PTEN, p53 Ser(15), PP1, and activated caspase-3 in HCT-116 and HT-29 cells were measured by Western blot. This study demonstrated that the expression of miR-200c was significantly higher in tumor tissues than in peritumoral tissues of colon cancer patients. The elevated miR-200c expression significantly correlated with the TNM stage, lymph node metastasis, and invasion of colon cancer. Silencing miR-200c expression significantly induced cell apoptosis, inhibited long-term survival, invasion, and metastasis, and delayed xenograft tumor growth. Importantly, silencing miR-200c expression sensitized the therapeutic effect of Ara-C (Cytarabine). The effects of silencing miR-200c expression were associated with upregulation of PTEN protein and p53 Ser(15) phosphorylation levels in HCT-116 cells and PTEN protein expression in HT-29 cells. In conclusion, miR-200c functions as an oncogene in colon cancer cells through regulating tumor cell apoptosis, survival, invasion, and metastasis as well as xenograft tumor growth through inhibition of PTEN expression and p53 phosphorylation.

STAT5-mediated expression of oncogenic miR-155 in cutaneous T-cell lymphoma

The pathogenesis of cutaneous T-cell lymphoma (CTCL) remains elusive. Recent discoveries indicate that the oncogenic microRNA miR-155 is overexpressed in affected skin from CTCL patients. Here, we address what drives the expression of miR-155 and investigate its role in the pathogenesis of CTCL. We show that malignant T cells constitutively express high levels of miR-155 and its host gene BIC (B cell integration cluster). Using ChIP-seq, we identify BIC as a target of transcription factor STAT5, which is aberrantly activated in malignant T cells and induced by IL-2/IL-15 in non-malignant T cells. Incubation with JAK inhibitor or siRNA-mediated knockdown of STAT5 decreases BIC/miR-155 expression, whereas IL-2 and IL-15 increase their expression in cell lines and primary cells. In contrast, knockdown of STAT3 has no effect, and BIC is not a transcriptional target of STAT3, indicating that regulation of BIC/miR-155 expression by STAT5 is highly specific. Malignant proliferation is significantly inhibited by an antisense-miR-155 as well as by knockdown of STAT5 and BIC.   In conclusion, we provide the first evidence that STAT5 drives expression of oncogenic BIC/miR-155 in cancer. Moreover, our data indicate that the STAT5/BIC/miR-155 pathway promotes proliferation of malignant T cells, and therefore is a putative target for therapy in CTCL.

Genes involved in the transition from normal epithelium to intraepithelial neoplasia are associated with colorectal cancer patient survival

Whether the heterogeneity in tumor cell morphology and behavior is the consequence of a progressive accumulation of genetic alterations or an intrinsic property of cancer-initiating cells established at initiation remains controversial. The hypothesis of biological predetermination in human cancer was proposed many years ago and states that the biological potency of cancer cells is predestinated in the precancerous stage. The present study aimed to investigate whether the aberrant molecular events occurring in initial cancer stages could eventually influence colorectal cancer (CRC) progression. We analyzed the mRNA and miRNA expression profiles of colorectal normal mucosa, low-grade intraepithelial neoplasia (LIN), high-grade intraepithelial neoplasia (HIN), and adenocarcinoma tissues. Compared with the transitions from LIN to HIN to invasive carcinoma, the transition from normal epithelium to LIN appeared to be associated with greater changes in the number and expression levels of mRNAs and miRNAs, with a differential expression of 2322 mRNAs and 71 miRNAs detected. Utilizing these early molecular changes, a miRNA-hub network analysis showed that 166 genes were identified as targets regulated by 30 miRNAs. Among these genes, a 55-gene signature regulated by 5 miRNAs was shown to be associated with overall survival or disease-free survival in three independent sample sets. Thus, the molecular changes in the transcriptome associated with the transition from normal to intraepithelial neoplasm may influence CRC progression.

Identification of serum microRNA profiles in colon cancer

Background:

microRNAs (miRNAs) exist in blood in an apparently stable form. We have explored whether serum miRNAs can be used as non-invasive early biomarkers of colon cancer.

Methods:

Serum samples from 30 patients with colon cancer stage IV and 10 healthy controls were examined for the expression of 375 cancer-relevant miRNAs. Based on the miRNA profile in this study, 34 selected miRNAs were measured in serum from 40 patients with stage I–II colon cancer and from 10 additional controls.

Results:

Twenty miRNAs were differentially expressed in serum from stage IV patients compared with controls (P<0.01). Unsupervised clustering revealed four subgroups; one corresponding mostly to the control group and the three others to the patient groups. Of the 34 miRNAs measured in the follow-up study of stage I–II patients, 21 showed concordant expression between stage IV and stage I–II patient. Based on the profiles of these 21 miRNAs, a supervised linear regression analysis (Partial Least Squares Regression) was performed. Using this model we correctly assigned stage I–II colon cancer patients based on miRNA profiles of stage IV patients.

Conclusion:

Serum miRNA expression profiling may be utilised in early detection of colon cancer.

Adrenaline promotes cell proliferation and increases chemoresistance in colon cancer HT29 cells through induction of miR-155

Recently, catecholamines have been described as being involved in the regulation of cancer genesis and progression. Here, we reported that adrenaline increased the cell proliferation and decreased the cisplatin induced apoptosis in HT29 cells. Further study found that adrenaline increased miR-155 expression in an NFκB dependent manner. HT29 cells overexpressing miR-155 had a higher cell growth rate and more resistance to cisplatin induced apoptosis. In contrast, HT29 cells overexpressing miR-155 inhibitor displayed decreased cell proliferation and sensitivity to cisplatin induced cell death. In summary, our study here revealed that adrenaline-NFκB-miR-155 pathway at least partially contributes to the psychological stress induced proliferation and chemoresistance in HT29 cells, shedding light on increasing the therapeutic strategies of cancer chemotherapy.