MicroRNAs in colorectal cancer: Role in metastasis and clinical perspectives

Epigenetically Regulating Non-coding RNAs in Colorectal Cancer: Promises and Potentials

Colorectal cancer (CRC) is a common malignancy with high mortality. Despite advancements in understanding its molecular causes and improved drug therapies, patient survival rates remain low. The main reasons for the high mortality rate are cancer metastasis and the emergence of drug-resistant cancer cell populations. While genetic changes are recognized as the main driver of CRC occurrence and progression, recent studies suggest that epigenetic regulation is a crucial marker in cancer, influencing the interplay between genetics and the environment. Research has shown the significant regulatory roles of non-coding RNAs (ncRNAs) in CRC development. This review explores epigenetically regulated ncRNAs and their functions, aiming to understand key regulatory mechanisms that impact CRC development. Additionally, it discusses the potential use of these ncRNAs in CRC diagnosis, prognosis, and targeted treatments.

Bringing to Light the Importance of the miRNA Methylome in Colorectal Cancer Prognosis Through Electrochemical Bioplatforms

This work reports the first electrochemical bioplatforms developed for the determination of the total contents of either target miRNA or methylated target miRNA. The bioplatforms are based on the hybridization of the target miRNA with a synthetic biotinylated DNA probe, the capture of the formed DNA/miRNA heterohybrids on the surface of magnetic microcarriers, and their recognition with an antibody selective to these heterohybrids or to the N6-methyladenosine (m6A) epimark. The determination of the total or methylated target miRNA was accomplished by labeling such secondary antibodies with the horseradish peroxidase (HRP) enzyme. In both cases, amperometric transduction was performed on the surface of disposable electrodes after capturing the resulting HRP-tagged magnetic bioconjugates. Because of their increasing relevance in colorectal cancer (CRC) diagnosis and prognosis, miRNA let-7a and m6A methylation were selected. The proposed electrochemical bioplatforms showed attractive analytical and operational characteristics for the determination of the total and m6A-methylated target miRNA in less than 75 min. These bioplatforms, innovative in design and application, were applied to the analysis of total RNA samples extracted from cultured cancer cells with different metastatic profiles and from paired healthy and tumor tissues of patients diagnosed with CRC at different stages. The obtained results demonstrated, for the first time using electrochemical platforms, the potential of interrogating the target miRNA methylation level to discriminate the metastatic capacities of cancer cells and to identify tumor tissues and, in a pioneering way, the potential of the m6A methylation in miRNA let-7a to serve as a prognostic biomarker for CRC.

Role of Post-Translational Modifications in Colorectal Cancer Metastasis

Colorectal cancer (CRC) is one of the most common malignant tumors of the digestive tract. CRC metastasis is a multi-step process with various factors involved, including genetic and epigenetic regulations, which turn out to be a serious threat to CRC patients. Post-translational modifications (PTMs) of proteins involve the addition of chemical groups, sugars, or proteins to specific residues, which fine-tunes a protein's stability, localization, or interactions to orchestrate complicated biological processes. An increasing number of recent studies suggest that dysregulation of PTMs, such as phosphorylation, ubiquitination, and glycosylation, play pivotal roles in the CRC metastasis cascade. Here, we summarized recent advances in the role of post-translational modifications in diverse aspects of CRC metastasis and its detailed molecular mechanisms. Moreover, advances in drugs targeting PTMs and their cooperation with other anti-cancer drugs, which might provide novel targets for CRC treatment and improve therapeutic efficacy, were also discussed.

Novel insights on perils and promises of miRNA in understanding colon cancer metastasis and progression

Colorectal cancer (CRC) is the third highest frequent malignancy and ultimate critical source of cancer-associated mortality around the world. Regardless of latest advances in molecular and surgical targeted medicines that have increased remedial effects in CRC patients, the 5-year mortality rate for CRC patients remains dismally low. Evidence suggests that microRNAs (miRNAs) execute an essential part in the development and spread of CRC. The miRNAs are a type of short non-coding RNA that exhibited to control the appearance of tumor suppressor genes and oncogenes. miRNA expression profiling is already being utilized in clinical practice as analytical and prognostic biomarkers to evaluate cancer patients' tumor genesis, advancement, and counteraction to drugs. By modulating their target genes, dysregulated miRNAs are linked to malignant characteristics (e.g., improved proliferative and invasive capabilities, cell cycle aberration, evasion of apoptosis, and promotion of angiogenesis). This review presents an updated summary of circulatory miRNAs, tumor-suppressive and oncogenic miRNAs, and the potential reasons for dysregulated miRNAs in CRC. Further we will explore the critical role of miRNAs in CRC drug resistance.

MicroRNA‑153 may act as a potential biomarker and prognostic indicator of patients with gastric cancer

MicroRNA (miR/miRNA)-153, as a novel tumor-related miRNA, has been found to be aberrantly expressed in different types of cancer; however, to the best of our knowledge, the role of miR-153 in gastric cancer (GC) remains unclear. The present study demonstrated that miR-153 expression was markedly decreased in GC, including GC cell lines and culture medium, GC tissues, and serum samples, based on reverse transcription-quantitative PCR, and this was further confirmed by fluorescence in situ hybridization. Transfection with miR-153 mimics inhibited proliferation and migration, and promoted apoptosis in GC cells. The serum expression levels of miR-153 were decreased in 59 patients with GC compared with those of 9 healthy controls, and more decreased in advanced GC compared with early-stage GC, suggesting that miR-153 was associated with tumor progression. Furthermore, serum miR-153 was expressed at significantly lower levels in patients with GC with larger tumor size (≥4 cm; P=0.013), poor differentiation and signet histology (P=0.013), lymph node metastasis (P=0.025) and advanced tumor stage (TNM stage III and IV; P=0.048) compared with patients with a smaller tumor size (<4 cm), well and moderate differentiation, no lymph node metastasis, and TNM stage I and II, respectively. In conclusion, the present study revealed that low miR-153 expression was associated with poor prognosis in GC and miR-153 may potentially act as a tumor biomarker and therapeutic target in GC.

Recent advances in the diagnostic and therapeutic roles of microRNAs in colorectal cancer progression and metastasis

Colorectal cancer (CRC) is the third most common malignancy in the world and one of the leading causes of cancer death; its incidence is still increasing in most countries. The early diagnostic accuracy of CRC is low, and the metastasis rate is high, resulting in a low survival rate of advanced patients. MicroRNAs (miRNAs) are a small class of noncoding RNAs that can inhibit mRNA translation and trigger mRNA degradation, and can affect a variety of cellular and molecular targets. Numerous studies have shown that miRNAs are related to tumour progression, immune system activity, anticancer drug resistance, and the tumour microenvironment. Dysregulation of miRNAs occurs in a variety of malignancies, including CRC. In this review, we summarize the recent research progress of miRNAs, their roles in tumour progression and metastasis, and their clinical value as potential biomarkers or therapeutic targets for CRC. Furthermore, we combined the roles of miRNAs in tumorigenesis and development with the therapeutic strategies of CRC patients, which will provide new ideas for the diagnosis and treatment of CRC.

Predictive Efficacy of Circulating Tumor Cells in First Drainage Vein Blood from Patients with Colorectal Cancer liver Metastasis

Circulating tumor cells (CTCs) are associated with metastasis. However, the low rate of detection of CTCs in peripheral vein blood (PVB) limits their clinical application. In this study, we observed higher positive rates of CTC in first drainage vein blood (FDVB) relative to peripheral venous blood (P < 0.001). Moreover, the CTC content was related to liver metastasis, T stage and CA19-9 levels. Our collective data suggest that CTCs in FDVB have good predictive utility for risk of liver metastasis of colorectal cancer (CRC), in particular, metachronous liver metastasis.

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.

Molecular Landscape of Small Bowel Adenocarcinoma

Small bowel adenocarcinoma (SBA) is a rare malignancy, with lower incidence, later stage at diagnosis, and poor overall prognosis compared to other cancers of the gastrointestinal tract. Owing to the rarity of the disease along with the paucity of high-quality tissue samples and preclinical models, little is known about the molecular alterations characteristic of SBA. This is reflected by the fact that the clinical management of SBA is primarily extrapolated from colorectal cancer (CRC). Recent advances in genomic profiling have highlighted key differences between these tumors, establishing SBA as a molecularly unique intestinal cancer. Moreover, comprehensive molecular analysis has identified a relatively high incidence of potentially targetable genomic alterations in SBA, predictive of response to targeted and immunotherapies. Further advances in our knowledge of the mutational and transcriptomic landscape of SBA, guided by an increased understanding of the molecular drivers of SBA, will provide opportunities to develop novel diagnostic tools and personalized therapeutic strategies.

Targeting of MAD2L1 by miR-515-5p involves the regulation of cell cycle arrest and apoptosis of colorectal cancer cells

Although many previous studies have found that the mitotic arrest deficient 2-like 1 (MAD2L1) protein contributes to the proliferation of colorectal cancer (CRC) cells, but the upstream mechanism of MAD2L1 is still largely elusive. This study aimed to explore the miRNAs upstream of MAD2L1 to improve our understanding of the mechanism of the MAD2L1 gene in CRC. The upstream target miRNAs (miR-515-5p) of MAD2L1 were predicted by the online databases miRWalk, miRDIP and TargetScan. Quantitative real-time PCR (qRT-PCR) was used to detect the expression level of miR-515-5p in human CRC tissues. The targeting relationship between miR-515-5p and MAD2L1 was tested by dual luciferase reporter gene assays. The effects of miR-515-5p on the biological behaviors of CRC cells by regulating MAD2L1 expression were verified by qRT-PCR, western blot, CCK-8, and flow cytometry. The results showed that miR-515-5p was a highly reliable upstream miRNA of the MAD2L1 gene. As an upstream target miRNA of MAD2L1, miR-515-5p was lowly expression in CRC tissues. The overexpression of miR-515-5p could inhibit the proliferation of CRC cells and induce cell cycle arrest at the G1 phase leading to cell apoptosis. However, MAD2L1 gene overexpression could reverse the effects of miR-515-5p overexpression on the biological behaviors of CRC cells above. This study illustrated that miR-515-5p can inhibit proliferation and induce G1 phase arrest leading to apoptosis in CRC cells. The mechanism underlying this phenomenon may be related to the negative targeted regulation of MAD2L1. This article is protected by copyright. All rights reserved.

Chemosensitivity analysis and study of gene resistance on tumors and cancer stem cell isolates from patients with colorectal cancer

Colorectal cancer (CRC) is one of the main causes of mortality. Recent studies suggest that cancer stem cells (CSCs) can survive after chemotherapy and promote tumor invasiveness and aggression. According to a higher hierarchy complexity of CSC, different protocols for isolation, expansion, and characterization have been used; however, there are no available resistance biomarkers that allow predicting the clinical response of treatment 5‑fluorouracil (5FU) and oxaliplatin. Therefore, the primary aim of the present study was to analyze the expression of gene resistance on tumors and CSC‑derived isolates from patients CRC. In the present study, adenocarcinomas of the colon and rectum (CRAC) were classified based on an in vitro adenosine triphosphate‑based chemotherapy response assay, as sensitive and resistant and the percentage of CD24 and CD44 markers are evaluated by immunohistochemistry. To isolate resistant colon‑CSC, adenocarcinoma tissues resistant to 5FU and oxaliplatin were evaluated. Finally, all samples were sequenced using a custom assay with chemoresistance‑associated genes to find a candidate gene on resistance colon‑CSC. Results showed that 59% of the CRC tissue analyzed was resistant and had a higher percentage of CD44 and CD24 markers. An association was found in the expression of some genes between the tumor‑resistant tissue and CSC. Overall, isolates of the CSC population CD44+ resistant to 5FU and oxaliplatin demonstrated different expression profiles; however, the present study was able to identify overexpression of the KRT‑18 gene, in most of the isolates. In conclusion, the results of the present study showed overexpression of KRT‑18 in CD44+ cells is associated with chemoresistance to 5FU and oxaliplatin in CRAC.

The association of immunosurveillance and distant metastases in colorectal cancer

Background

Colorectal cancer (CRC) is the third most common malignancy worldwide, but the key driver to distant metastases is still unknown. This study aimed to elucidate the link between immunosurveillance and organotropism of metastases in CRC by evaluating different gene signatures and pathways.

Material and methods

CRC patients undergoing surgery at the Department of General, Visceral and Transplantation Surgery at the Ludwig-Maximilian University Hospital Munich (Munich, Germany) were screened and categorized into M0 (no distant metastases), HEP (liver metastases) and PER (peritoneal carcinomatosis) after a 5-year follow-up. Six patients of each group were randomly selected to conduct a NanoString analysis, which includes 770 genes. Subsequently, all genes were further analyzed by gene set enrichment analysis (GSEA) based on seven main cancer-associated databases.

Results

Comparing HEP vs. M0, the gene set associated with the Toll-like receptor (TLR) cascade defined by the Reactome database was significantly overrepresented in HEP. HSP90B1, MAPKAPK3, PPP2CB, PPP2R1A were identified as the core enrichment genes. The immunologic signature pathway GSE6875_TCONV_VS_FOXP3_KO_TREG_DN with FOXP3 as downstream target was significantly overexpressed in M0. RB1, TMEM 100, CFP, ZKSCAN5, DDX50 were the core enrichment genes. Comparing PER vs. M0 no significantly differentially expressed gene signatures were identified.

Conclusion

Chronic inflammation might enhance local tumor growth. This is the first study identifying immune related gene sets differentially expressed between patients with either liver or peritoneal metastases. The present findings suggest that the formation of liver metastases might be associated with TLR-associated pathways. In M0, a high expression of FOXP3 + tumor infiltrating lymphocytes (TILs) seemed to prevent at least in part metastases. Thus, these correlative findings lay the cornerstone to further studies elucidating the underlying mechanisms of organotropism of metastases.

Biological Implications and Clinical Potential of Metastasis-Related miRNA in Colorectal Cancer

Colorectal cancer (CRC), ranking as the third commonest cancer, leads to extremely high rates of mortality. Metastasis is the major cause of poor outcome in CRC. When metastasis occurs, 5-year survival rates of patients decrease sharply, and strategies to enhance a patient's lifetime seem limited. MicroRNAs (miRNAs) are evolutionarily conserved small non-coding RNAs that are significantly involved in manipulation of CRC malignant phenotypes, including proliferation, invasion, and metastasis. To date, accumulating studies have revealed the mechanisms and functions of certain miRNAs in CRC metastasis. However, there is no systematic discussion about the biological implications and clinical potential (diagnostic role, prognostic role, and targeted therapy potential) of metastasis-related miRNAs in CRC. This review mainly summarizes the recent advances of miRNA-mediated metastasis in CRC. We also discuss the clinical values of metastasis-related miRNAs as potential biomarkers or therapeutic targets in CRC. Moreover, we envisage the future orientation and challenges in translating these findings into clinical applications.

Upregulated miR-410 is linked to poor prognosis in colorectal cancer

BACKGROUND

Although miR-410 acts as a cancer inducer in colorectal cancer, there is limited data on the clinical implications of miR-410 expression levels in patients. We hypothesized a link between miR-410 expression and its potential clinical values in patients with colorectal cancer.

MATERIAL AND METHODS

120 colorectal cancer tissue specimens and 120 adjacent non-tumour tissues were obtained. Quantification of miR-410 expression levels was determined by, quantitative RT-PCR. Expression was analysed by clinical features.

RESULTS

miR-410 was up-regulated in malignant tissues compared with corresponding normal tissues (P < 0.01), with TNM stage and lymph node metastasis (P = 0.03, P = 0.004, respectively), and with worse overall survival (P = 0.002). Multivariate survival analysis identified it as an independent risk factor for outcome (P = 0.021, HR = 2.19; 95% CI = 1.12-4.25).

CONCLUSION

Compared to normal non-cancerous tissues, miR-410 was overexpressed in tumour tissues and is independently associated with the unfavourable outcome. Levels of MiR-410 might a useful laboratory tool in managing and predicting the prognosis of colorectal cancer.

Identification of microRNAs and their Endonucleolytic Cleavaged target mRNAs in colorectal cancer

Background

Colorectal cancer (CRC) ranks the third among the most common malignancies globally. It is well known that microRNAs (miRNAs) play vital roles in destabilizing mRNAs and repressing their translations in this disease. However, the mechanism of miRNA-induced mRNA cleavage remains to be investigated.

Method

In this study, high-throughput small RNA (sRNA) sequencing was utilized to identify and profile miRNAs from six pairs of colorectal cancer tissues (CTs) and adjacent tissues (CNs). Degradome sequencing (DS) was employed to detect the cleaved target genes. The Database for Annotation, Visualization and Integrated Discovery (DAVID) software was used for GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analysis.

Results

In total, 1278 known miRNAs (clustered into 337 families) and 131 novel miRNAs were characterized in the CT and CN libraries, respectively. Of those, 420 known and eight novel miRNAs were defined as differentially expressed miRNAs (DEmiRNAs) by comparing the expression levels observed in the CT and CN libraries. Furthermore, through DS, 9685 and 202 potential target transcripts were characterized as target genes for 268 known and 33 novel miRNAs, respectively. It was further predicted that a total of 264 targeted genes for the 85 DEmiRNAs are involved in proteoglycans in cancer and the AMP-activated protein kinase signaling pathway. After systemic analysis of prognosis-related miRNA targets in those cancer-related signal pathways, we found that two targets ezrin (EZR) and hematopoietic cell-specific Lyn substrate 1 (HCLS1) had the potential prognostic characteristics with CRC regarding over survival (OS) or recurrence.

Conclusion

In total, we found that endonucleolytic miRNA-directed mRNA cleavage occurs in CRC. A number of potential genes targeted by CRC-related miRNAs were identified and some may have the potential as prognosis markers of CRC. The present findings may lead to an improved better appreciation of the novel interaction mode between miRNAs and target genes in CRC.

MicroRNA-145 Inhibits Cell Migration and Invasion in Colorectal Cancer by Targeting TWIST

INTRODUCTION

MicroRNAs function as oncogenes or tumor suppressors in the development of various human cancers. We investigated the effect of microRNA-145 (miR-145) on colorectal cancer (CRC) cell invasion and migration.

METHODS

The levels of miR-145 in CRC cells were examined by quantitative PCR; Western blotting was used to detect TWIST1 (twist family bHLH transcription factor 1) protein and the epithelial-mesenchymal transition (EMT)-related proteins (E-cadherin, vimentin). Then, we transfected miR-145 mimics or inhibitor into CRC cells and used the wound healing and Transwell invasion assays to investigate their migration and invasive capability, respectively.

RESULTS

The miR-145 mimics suppressed CRC cell invasion and migration significantly; in contrast, miR-145 downregulation had the opposite effect. Furthermore, miR-145 regulated TWIST1 levels negatively at transcriptional level. TWIST1 knockdown significantly inhibited the CRC cell migration ability and the number of CRC cells that crossed the Transwell membrane. There was no significant difference in terms of migration and invasive capability after the cells had been transfected with miR-145 mimics or inhibitor plus TWIST1 small interfering RNA (siRNA) as compared to the TWIST1 siRNA-only group. Furthermore, we demonstrate that the inhibition of miR-145 could enhance the capability for lung metastasis in vivo.

CONCLUSION

Taken together, these findings indicate that miR-145 acts as a new tumor suppressor by regulating TWIST1 and plays a vital role in the invasive and migration ability of CRC cells.

Small non-coding RNA and colorectal cancer

Colorectal cancer (CRC) is the third most common malignance. Although great efforts have been made to understand the pathogenesis of CRC, the underlying mechanisms are still unclear. It is now clear that more than 90% of the total genome is actively transcribed, but lack of protein-coding potential. The massive amount of RNA can be classified as housekeeping RNAs (such as ribosomal RNAs, transfer RNAs) and regulatory RNAs (such as microRNAs [miRNAs], PIWI-interacting RNA [piRNAs], tRNA-derived stress-induced RNA, tRNA-derived small RNA [tRFs] and long non-coding RNAs [lncRNAs]). Small non-coding RNAs are a group of ncRNAs with the length no more than 200 nt and they have been found to exert important regulatory functions under many pathological conditions. In this review, we summarize the biogenesis and functions of regulatory sncRNAs, such as miRNAs, piRNA and tRFs, and highlight their involvements in cancers, particularly in CRC.

microRNA-193a-5p inhibits migration of human HT-29 colon cancer cells via suppression of metastasis pathway

PURPOSE

Altered expression of microRNAs (miRNAs) is indicated strongly in colorectal cancer (CRC). This study aims to evaluate the inhibitory role of miR-193a-5p on epithelial-mesenchymal transition markers in CRC lines. The cellular effects and potential mechanisms of miR-193a-5p were also examined.

METHODS

Quantitative reverse-transcription polymerase chain reaction (RT-PCR) was performed to determine the expression of miR-193a-5p in three CRC cell lines (HCT-116, SW-480, and HT-29) and its impact on metastasis-related genes ( vimentin and CXCR4) before and after mimic transfection. Of those, the cell line with the highest changes was selected for the next upcoming experiments such as wound-healing assay, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), and annexin-V staining tests.

RESULTS

Our results revealed that miR-193a-5p was significantly downregulated in three CRC cell lines and that HT-29 displayed the most decrease ( P < 0.0001). The restoration of miR-193a-5p in human HT-29 cell line inhibited cell migration. But, miR-193a-5p transfection did not affect cell viability and had no significant effect on apoptosis induction. Also, the quantitative RT-PCR analysis of miR-193a-5p mimic transfected cells revealed a significant increase in miR-193a-5p messenger RNA (mRNA) expression level ( P < 0.0001) with reduction of vimentin and CXCR4 mRNA expression levels in HT-29 cell line ( P < 0.01 and < 0.05, respectively).

CONCLUSION

Our results indicated that miR-193a-5p acts as a tumor suppressor miRNA and its downregulation plays an important role in metastasis via upregulation of metastasis-related genes in CRC. Therefore, it can be considered as a potential therapeutic target for applying in CRC management in the future.

DNA methylation and chromatin modifiers in colorectal cancer

Colorectal carcinogenesis is a multistep process involving the accumulation of genetic alterations over time that ultimately leads to disease progression and metastasis. Binding of transcription factors to gene promoter regions alone cannot explain the complex regulation pattern of gene expression during this process. It is the chromatin structure that allows for a high grade of regulatory flexibility for gene expression. Posttranslational modifications on histone proteins such as acetylation, methylation, or phosphorylation determine the accessibility of transcription factors to DNA. DNA methylation, a chemical modification of DNA that modulates chromatin structure and gene transcription acts in concert with these chromatin conformation alterations. Another epigenetic mechanism regulating gene expression is represented by small non-coding RNAs. Only very recently epigenetic alterations have been included in molecular subtype classification of colorectal cancer (CRC). In this chapter, we will provide examples of the different epigenetic players, focus on their role for epithelial-mesenchymal transition and metastatic processes and discuss their prognostic value in CRC.

Development of novel predictive miRNA/target gene pathways for colorectal cancer distance metastasis to the liver using a bioinformatic approach

Background

Liver metastases are the major cause of colorectal cancer (CRC)-related deaths. However, there is no reliable clinical predictor for CRC progression to liver metastasis. In this study, we investigated possible predictors (miRNAs and biomarkers) for clinical application.

Methodology

The Gene Expression Omnibus (GEO) datasets GSE49355, GSE41258 and GSE81558 for genes and GSE54088 and GSE56350 for miRNAs were used to identify common differentially expressed genes (DEGs) and miRNAs between primary CRC tissues and liver metastases. The identified miRNAs and their targets from the DEGs were verified in datasets comprising gene, miRNA and miRNA exosome profiles of CRC patients with no distant metastases (M0) and distant metastases (M1); the interaction networks and pathways were also mapped.

Results

There were 49 upregulated and 13 downregulated DEGs and 16 downregulated and 14 upregulated miRNAs; between the DEGs and miRNA targets, there were five upregulated and four downregulated genes. MiR-20a was strongly correlated with the status of liver metastasis. MiR-20a, miR499a, and miR-576-5p were highly correlated with the metastatic outcomes. MiR-20a was significantly highly expressed in the M1 group. In an analysis of the miRNA target genes, we found that CDH2, KNG1, and MMP2 were correlated with CRC metastasis. We demonstrated a new possible pathway for CRC metastasis: miR-576-5p/F9, miR20a/MMP2, CTSK, MMP3, and miR449a/P2RY14. The regulation of IGF transport and uptake by IGFBPs, extracellular matrix organization, signal transduction and the immune system were the enriched pathways.

Conclusion

This model can predict CRC to liver metastases and the pathways involved, which can be clinically applicable.

MicroRNA-3191 promotes migration and invasion by downregulating TGFBR2 in colorectal cancer

Mutations in transforming growth factor beta receptor II (TGFBR2) are detected in up to 30% of overall colorectal cancer (CRC). Dysregulation of some microRNAs participated in the CRC pathogenesis. In this study, we used the gene ontology analyses, the Kyoto Encyclopedia of Genes and Genomes pathway analyses and gene set enrichment analysis to indicate that miR-3191 was involved in the regulation of transforming growth factor beta (TGF-BETA) signal pathway in CRC. These bioinformatics results were supported by data obtained from CRC samples and experiments in vitro. The luciferase reporter assay was used to confirm that miR-3191 modulates TGF-BETA signal pathway by targeting TGFBR2. By transwell migration and invasion assays, we showed that miR-3191 promoted CRC cell migration and invasion by downregulating TGFBR2. And it may serve as a novel therapeutic strategy for treating CRC patients.

miR-196a-5p promotes metastasis of colorectal cancer via targeting IκBα

Background

MicroRNA-196a-5p (miR-196a-5p) has been reported to be involved in the metastatic process of several cancers. In present work, we aimed to investigate the effects of miR-196a-5p and its potential target IκBα on migration, invasion and epithelial-mesenchymal transition (EMT) of colorectal cancer (CRC) cells.

Methods

CCK-8 assay, wound healing assay and cell invasion assay were performed to evaluate the cell proliferation, migration and invasion. In vivo metastasis models were used to investigate the tumor metastasis ability. Real-time PCR, immunofluorescence staining or western blot were utilized to detect the expression of miR-196a-5p, IκBα, p-IκBα, nuclear p65 and EMT markers including E-cadherin, N-cadherin and fibronectin. Dual luciferase reporter assay was carried out to determine whether there is a direct interaction between miR-196a-5p and IκBα mRNA.

Results

Using SW480 cell with miR-196-5p over-expressed plus SW620 and HCT116 cells with miR-196a-5p knockdown, we found that miR-196a-5p promoted cell proliferation, migration and invasion in vitro and facilitated liver metastasis in vivo. We also observed that miR-196a-5p knockdown or NF-κB pathway inhibition up-regulated E-cadherin while down-regulated N-cadherin and fibronectin. By contrast, miR-196a-5p over-expression promoted EMT process of CRC. Data of dual luciferase reporter assay indicated that miR-196a-5p targeted the IκBα. Moreover, miR-196a-5p down-regulated IκBα expression while up-regulated nuclear p65 expression. Additionally, over-expression of IκBα in CRC cells attenuated the effects of miR-196a-5p on cell migration, invasion and EMT.

Conclusions

miR-196a-5p may play a key role in EMT, invasion and metastasis of CRC cells via targeting the IκBα.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-5245-1) contains supplementary material, which is available to authorized users.

MicroRNA-383 acts as a tumor suppressor in colorectal cancer by modulating CREPT/RPRD1B expression

CREPT (Cell-cycle-related and expression-elevated protein in tumor)/RPRD1B, a novel protein that enhances the transcription of Cyclin D1 to promote cell proliferation during tumorigenesis, was demonstrated highly expressed in most of tumors. However, it remains unclear how CREPT is regulated in colorectal cancers. In this study, we report that miR-383 negatively regulates CREPT expression. We observed that CREPT was up-regulated but the expression of miR-383 was down regulated in both colon cancer cell lines and colon tumor tissues. Intriguingly, we found that enforced expression of miR-383 inhibited the expression of CREPT at both the mRNA and protein level. Using a luciferase reporter, we showed that miR-383 targeted the 3'-UTR of CREPT mRNA directly. Consistently we observed that over expression of miR-383 shortened the half-life of CREPT mRNA in varieties of colorectal cancer cells. Furthermore, restoration of miR-383 inhibited cell growth and colony formation of colon cancer cells accompanied by inhibition of expression of CREPT and related downstream genes. Finally, we demonstrated that stable over expression of miR-383 in colon cancer cells decreased the growth of the tumors. Our results revealed that the abundant expression of CREPT in colorectal cancers is attributed to the decreased level of miR-383. This study shed a new light on the potential therapeutic therapy strategy for colorectal cancers using introduced miRNA.

Noninvasive Biomarkers of Colorectal Cancer: Role in Diagnosis and Personalised Treatment Perspectives

Colorectal cancer (CRC) is the third leading cause of cancer-related deaths worldwide. It has been estimated that more than one-third of patients are diagnosed when CRC has already spread to the lymph nodes. One out of five patients is diagnosed with metastatic CRC. The stage of diagnosis influences treatment outcome and survival. Notwithstanding the recent advances in multidisciplinary management and treatment of CRC, patients are still reluctant to undergo screening tests because of the associated invasiveness and discomfort (e.g., colonoscopy with biopsies). Moreover, the serological markers currently used for diagnosis are not reliable and, even if they were useful to detect disease recurrence after treatment, they are not always detected in patients with CRC (e.g., CEA). Recently, translational research in CRC has produced a wide spectrum of potential biomarkers that could be useful for diagnosis, treatment, and follow-up of these patients. The aim of this review is to provide an overview of the newer noninvasive or minimally invasive biomarkers of CRC. Here, we discuss imaging and biomolecular diagnostics ranging from their potential usefulness to obtain early and less-invasive diagnosis to their potential implementation in the development of a bespoke treatment of CRC.

Long noncoding RNA DANCR promotes colorectal cancer proliferation and metastasis via miR-577 sponging

Long non-coding RNAs (lncRNAs) play key roles in various malignant tumors, including colorectal cancer (CRC). Long non-coding RNA differentiation antagonizing non-protein coding RNA (DANCR) is overexpressed in CRC patients, but whether it affects CRC proliferation and metastasis via regulation of heat shock protein 27 (HSP27) remains unclear. In the present study, we found that DANCR was highly expressed and correlated with proliferation and metastasis in CRC. In addition, we demonstrated that DANCR and HSP27 were both targets of microRNA-577 (miR-577) and shared the same binding site. Furthermore, we revealed that DANCR promoted HSP27 expression and its mediation of proliferation/metastasis via miR-577 sponging. Finally, using an in vivo study, we confirmed that overexpression of DANCR promoted CRC tumor growth and liver metastasis. The present study demonstrated the function of DANCR in CRC and might provide a new target in the treatment of CRC.

Circulating Plasma Levels of miR-20b, miR-29b and miR-155 as Predictors of Bevacizumab Efficacy in Patients with Metastatic Colorectal Cancer

Targeting angiogenesis in the treatment of colorectal cancer (CRC) is a common strategy, for which potential predictive biomarkers have been studied. miRNAs are small non-coding RNAs involved in several processes including the angiogenic pathway. They are very stable in biological fluids, which turns them into potential circulating biomarkers. In this study, we considered a case series of patients with metastatic (m) CRC treated with a bevacizumab (B)-based treatment, enrolled in the prospective multicentric Italian Trial in Advanced Colorectal Cancer (ITACa). We then analyzed a panel of circulating miRNAs in relation to the patient outcome. In multivariate analysis, circulating basal levels of hsa-miR-20b-5p, hsa-miR-29b-3p and hsa-miR-155-5p resulted in being significantly associated with progression-free survival (PFS) (p = 0.027, p = 0.034 and p = 0.039, respectively) and overall survival (OS) (p = 0.044, p = 0.024 and p = 0.032, respectively). We also observed that an increase in hsa-miR-155-5p at the first clinical evaluation was significantly associated with shorter PFS (HR 3.03 (95% CI 1.06-9.09), p = 0.040) and OS (HR 3.45 (95% CI 1.18-10.00), p = 0.024), with PFS and OS of 9.5 (95% CI 6.8-18.7) and 15.9 (95% CI 8.4-not reached), respectively, in patients with an increase ≥30% of hsa-miR-155-5p and 22.3 (95% CI 10.2-25.5) and 42.9 (24.8-not reached) months, respectively, in patients without such increase. In conclusion, our results highlight the potential usefulness of circulating basal levels of hsa-miR-20b-5p, hsa-miR-29b-3p and hsa-miR-155-5p in predicting the outcome of patients with mCRC treated with B. In addition, the variation of circulating hsa-miR-155-5p could also be indicative of the patient survival.

Decoding colorectal cancer epigenomics

Colorectal cancer (CRC) is very heterogeneous and presents different types of epigenetic alterations including DNA methylation, histone modifications and microRNAs. These changes are considered as characteristics of various observed clinical phenotypes. Undoubtedly, the discovery of epigenetic pathways with novel epigenetic-related mechanisms constitutes a promising advance in cancer biomarker discovery. In this review, we provide an evidence-based discussing of the current understanding of CRC epigenomics and its role in initiation, epithelial-to-mesenchymal transition and metastasis. We also discuss the recent findings regarding the potential clinical perspectives of these alterations as potent biomarkers for CRC diagnosis, prognosis, and therapy in the era of liquid biopsy.

MicroRNAs in the etiology of colorectal cancer: pathways and clinical implications

MicroRNAs (miRNAs) are small single-stranded RNAs that repress mRNA translation and trigger mRNA degradation. Of the ∼1900 miRNA-encoding genes present in the human genome, ∼250 miRNAs are reported to have changes in abundance or altered functions in colorectal cancer. Thousands of studies have documented aberrant miRNA levels in colorectal cancer, with some miRNAs reported to actively regulate tumorigenesis. A recurrent phenomenon with miRNAs is their frequent participation in feedback loops, which probably serve to reinforce or magnify biological outcomes to manifest a particular cellular phenotype. Here, we review the roles of oncogenic miRNAs (oncomiRs), tumor suppressive miRNAs (anti-oncomiRs) and miRNA regulators in colorectal cancer. Given their stability in patient-derived samples and ease of detection with standard and novel techniques, we also discuss the potential use of miRNAs as biomarkers in the diagnosis of colorectal cancer and as prognostic indicators of this disease. MiRNAs also represent attractive candidates for targeted therapies because their function can be manipulated through the use of synthetic antagonists and miRNA mimics.

Summary: This Review provides an overview of some important microRNAs and their roles in colorectal cancer.

miR-422a inhibits cell proliferation in colorectal cancer by targeting AKT1 and MAPK1

BACKGROUND

miRNAs are regarded as molecular biomarkers and therapeutic targets for colorectal cancer (CRC), a series of miRNAs have been proven to involve into CRC carcinogenesis, invasion and metastasis. Aberrant miR-422a expression and its roles have been reported in some cancers. However, the function and underlying mechanism of miR-422a in the progression of CRC remain largely unknown.

METHODS

Real-time PCR were used to quantify miR-422a expression in CRC tissues. Both vivo and vitro functional assays showed miR-422a inhibits CRC cell proliferation. Target prediction program (miRBase) and luciferase reporter assays were conducted to confirm the target genes AKT1 and MAPK1 of miR-422a. Specimens from 50 patients with CRC were analyzed for the correlation between the expression of miR-422a and the expression of the target genes AKT1 and MAPK1 by real-time PCR.

RESULTS

MiR-422a was down‑regulated in CRC tissues and cell lines. Ectopic expression of miR-422a inhibited cell proliferation and tumor growth ability; inhibition of endogenous miR-422a, by contrast, promoted cell proliferation and tumor growth ability of CRC cells. MiR-422a directly targets 3'-UTR of the AKT1 and MAPK1, down-regulation of miR-422a led to the activation of Raf/MEK/ERK and PI3K/AKT signaling pathways to promote cell proliferation in CRC. In addition, miR-422a expression was negatively correlated with the expressions of AKT1 and MAPK1 in CRC tissues.

CONCLUSION

miR-422a inhibits cell proliferation in colorectal cancer by targeting AKT1 and MAPK1.

microRNA-219-5p inhibits epithelial-mesenchymal transition and metastasis of colorectal cancer by targeting lymphoid enhancer-binding factor 1

Aberrant expression of microRNAs (miRs) has been shown to play a critical role in the pathogenesis and progression of tumors. microRNA‐219‐5p (miR‐219‐5p) has been reported to be abnormally expressed in some types of human tumors. However, the mechanism between miR‐219‐5p and colorectal cancer (CRC) metastasis remains unclear. In the present study, miR‐219‐5p was found to be downregulated in CRC tissue compared with matched normal tissue. Through luciferase reporter assay, we demonstrated lymphoid enhancer‐binding factor 1 (LEF1) as a direct target of miR‐219‐5p. Overexpression of miR‐219‐5p could inhibit motility, migration and invasion of CRC cells, and inhibit epithelial‐mesenchymal transition (EMT). Furthermore, silencing LEF1 phenocopied this metastasis‐suppressive function. The recovery experiment showed that re‐expression of LEF1 rescued this suppressive effect on tumor metastasis and reversed the expression of EMT markers caused by miR‐219‐5p. Additionally, we demonstrated that miR‐219‐5p exerted this tumor‐suppressive function by blocking activation of the AKT and ERK pathways. Finally, a nude mice experiment showed that miR‐219‐5p reduced the lung metastasis ability of CRC cells. Taken together, our findings indicate that miR‐219‐5p inhibits metastasis and EMT of CRC by targeting LEF1 and suppressing the AKT and ERK pathways, which may provide a new antitumor strategy to delay CRC metastasis.

Involvement of Non-coding RNAs in the Signaling Pathways of Colorectal Cancer

Colorectal cancer (CRC) is one of the most common diagnosed cancers worldwide. The metastasis and development of resistance to anti-cancer treatment are major challenges in the treatment of CRC. Understanding mechanisms underpinning the pathogenesis is therefore critical in developing novel agents for CRC treatments. A large number of evidence has demonstrated that non-coding RNAs (ncRNAs), including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs have functional roles in both the physiological and pathological processes by regulating the expression of their target genes. These molecules are engaged in the pathobiology of neoplastic diseases and are targets for the diagnosis, prognosis and therapy of a variety of cancers, including CRC. In this regard, ncRNAs have emerged as one of the hallmarks of CRC pathogenesis and they also play key roles in metastasis, drug resistance and the stemness of CRC stem cell by regulating various signaling networks. Therefore, a better understanding the ncRNAs involved in the signaling pathways of CRC may lead to the development of novel strategy for diagnosis, prognosis and treatment of CRC. In this chapter, we summarize the latest findings on ncRNAs, with a focus on miRNAs and lncRNAs involving in signaling networks and in the regulation of pathogenic signaling pathways in CRC.

A tumor-suppressive microRNA, miRNA-485-5p, inhibits glioma cell proliferation and invasion by down-regulating TPD52L2

Glioblastoma multiforme is the most deadly primary brain tumor and has no effective treatment. Therefore, it is important to identify novel and effective therapies that impede glioma tumorigenesis. MicroRNAs (miRNAs) are helpful analytical biomarkers and may be useful targets for treating multiple human cancers. Previous reports suggest that miRNA-485-5p is dysregulated and contributes to tumorigenesis in some cancer types. Nevertheless, the biological role of miRNA-485-5p in glioma is not well understood. In this study, we demonstrated that miRNA-485-5p expression was reduced in gliomat issues and cell lines. In addition, miRNA-485-5p overexpression inhibited cell proliferation, migration, and invasion in glioma cell lines. Additionally, we identified Tumor Protein D52 Like 2 (TPD52L2) as a direct target of miRNA-485-5p. Moreover, we showed that miRNA-485-5p regulated glioma tumorigenesis by down-regulating TPD52L2 expression in vitro and in vivo. Our results suggest that miRNA-485-5p is a suppressor of glioma tumorigenesis and could serve as a novel candidate for therapeutic applications in glioma treatment.

Silencing protein kinase C ζ by microRNA-25-5p activates AMPK signaling and inhibits colorectal cancer cell proliferation

Developing novel strategies against human colorectal cancer (CRC) cells is needed. Activation of AMP-activated protein kinase (AMPK) could possibly inhibit CRC cells. Protein kinase C ζ (PKCζ) is an AMPK negative regulator. Here we found that PKCζ expression was significantly elevated in human colon cancer tissues and CRC cells. PKCζ upregulation was correlated with AMPK in-activation and mTOR complex 1 (mTORC1) over-activation. Reversely, PKCζ shRNA knockdown activated AMPK signaling and inhibited HT-29 cell proliferation. Significantly, downregulation of microRNA-25-5p (miR-25-5p), a PKCζ-targeting miRNA, could be the cause of PKCζ upregulation. Exogenous expression of miR-25-5p silenced PKCζ to activate AMPK signaling, which inhibited HT-29 cell proliferation. In vivo studies showed that HT-29 xenograft growth in mice was inhibited after expressing PKCζ shRNA or miR-25-5p. Collectively, PKCζ could be a novel oncogenic protein of human CRC. PKCζ silence, by targeted-shRNA or miR-25-5p expression, activates AMPK and inhibits HT-29 cell proliferation.

Genetic and epigenetic markers in colorectal cancer screening: recent advances

INTRODUCTION

Colorectal cancer (CRC) is a heterogenous disease which develops from benign intraepithelial lesions known as adenomas to malignant carcinomas. Acquired alterations in Wnt signaling, TGFβ, MAPK pathway genes and clonal propagation of altered cells are responsible for this transformation. Detection of adenomas or early stage cancer in asymptomatic patients and better prognostic and predictive markers is important for improving the clinical management of CRC. Area covered: In this review, the authors have evaluated the potential of genetic and epigenetic alterations as markers for early detection, prognosis and therapeutic predictive potential in the context of CRC. We have discussed molecular heterogeneity present in CRC and its correlation to prognosis and response to therapy. Expert commentary: Molecular marker based CRC screening methods still fail to gain trust of clinicians. Invasive screening methods, molecular heterogeneity, chemoresistance and low quality test samples are some key challenges which need to be addressed in the present context. New sequencing technologies and integrated omics data analysis of individual or population cohort results in GWAS. MPE studies following a GWAS could be future line of research to establish accurate correlations between CRC and its risk factors. This strategy would identify most reliable biomarkers for CRC screening and management.

miR-944 inhibits cell migration and invasion by targeting MACC1 in colorectal cancer

Dysfunction of microRNAs (miRNAs) is strongly proved to participate in the pathogenesis and tumorigenicity of colorectal cancer (CRC). miR-944 was reported to play either oncogenic or tumor suppressive roles in human cancers. A recent study reported that the levels of miR-944 in recurrent CRC patients were evidently lower than that in non-recurrent cases, suggesting that miR-944 may function as a tumor suppressive miRNA in CRC. Yet, the clinical value and biological function of miR-944 remain rarely known in CRC. In the present study, we present that miR-944 level in CRC tissues is notably reduced compared to matched non-cancerous specimens. Its decreased level is evidently correlated with malignant clinical parameters and poor prognosis of CRC patients. Accordingly, the levels of miR-944 were obviously downregulated in CRC cells. Ectopic expression of miR-944 in CRC cells prominently inhibits the migration and invasion of tumor cells, while miR-944 knockdown increased these effects of CRC cells. Mechanically, miR-944 negatively regulated the metastasis-associated in colon cancer-1 (MACC1) abundance in CRC cells. Herein, MACC1 was found to be a downstream molecule of miR-944 in CRC. An inversely correlation between miR-944 and MACC1 was confirmed in CRC specimens. Furthermore, restoration of MACC1 expression could abrogate the anti-metastatic effects of miR-944 on CRC cells with enhanced cell migration and invasion. MACC1/Met/AKT signaling may be implicated with the function of miR-944 in CRC cells. Altogether, miR-944 potentially act as a prognostic predictor and a drug-target for CRC patients.

Overexpression of miR-10b in colorectal cancer patients: Correlation with TWIST-1 and E-cadherin expression

MicroRNAs are emergent players of epigenetics that function as oncogenes or tumor suppressors and that have been implicated in regulating diverse cellular pathways. MiR-10b is an oncogenic microRNA involved in tumor invasion and metastasis in various cancers. Our data have shown that miR-10b is overexpressed in colorectal cancer samples in comparison with non-tumorous adjacent mucosa (p = 0.0025) and that it is associated with severe features such as tumor size >5 cm (p = 0.023), distant metastasis (p = 0.0022), non-differentiated tumors (p = 0.016), and vascular invasion (p = 0.01). Regarding the regulation of its expression, positive correlation between the loss of miR-10b and aberrant DNA methylation (p = 0.02) as well as a loss of TWIST-1 messenger RNA (p = 0.018) have been observed. Furthermore, expression analysis of the downstream miR-10b targets has shown that there are associations between low HOXD10 messenger RNA and E-cadherin protein levels (p < 0.0001, p = 0.0008, respectively) and overexpression of miR-10b. Our data suggests that overexpression of miR-10b results from high levels of TWIST-1 and may induce a decrease of E-cadherin membranous protein levels, thus contributing to the acquisition of metastatic phenotypes in colorectal cancer.

The Role of Bioactive Dietary Components in Modulating miRNA Expression in Colorectal Cancer

Colorectal cancer is the third most common cancer in the world and considered to be one of the most diet-related types of cancer. Extensive research has been conducted but still the link between diet and colorectal cancer is complex. Recent studies have highlight microRNAs (miRNAs) as key players in cancer-related pathways in the context of dietary modulation. MicroRNAs are involved in most biological processes related to tumor development and progression; therefore, it is of great interest to understand the underlying mechanisms by which dietary patterns and components influence the expression of these powerful molecules in colorectal cancer. In this review, we discuss relevant dietary patterns in terms of miRNAs modulation in colorectal cancer, as well as bioactive dietary components able to modify gene expression through changes in miRNA expression. Furthermore, we emphasize on protective components such as resveratrol, curcumin, quercetin, α-mangostin, omega-3 fatty acids, vitamin D and dietary fiber, with a focus on the molecular mechanisms in the context of prevention and even treatment. In addition, several bioactive dietary components that have the ability to re-sensitize treatment resistant cells are described.

Asymmetric exponential amplification reaction on a toehold/biotin featured template: an ultrasensitive and specific strategy for isothermal microRNAs analysis

The sensitive and specific analysis of microRNAs (miRNAs) without using a thermal cycler instrument is significant and would greatly facilitate biological research and disease diagnostics. Although exponential amplification reaction (EXPAR) is the most attractive strategy for the isothermal analysis of miRNAs, its intrinsic limitations of detection efficiency and inevitable non-specific amplification critically restrict its use in analytical sensitivity and specificity. Here, we present a novel asymmetric EXPAR based on a new biotin/toehold featured template. A biotin tag was used to reduce the melting temperature of the primer/template duplex at the 5′ terminus of the template, and a toehold exchange structure acted as a filter to suppress the non-specific trigger of EXPAR. The asymmetric EXPAR exhibited great improvements in amplification efficiency and specificity as well as a dramatic extension of dynamic range. The limit of detection for the let-7a analysis was decreased to 6.02 copies (0.01 zmol), and the dynamic range was extended to 10 orders of magnitude. The strategy enabled the sensitive and accurate analysis of let-7a miRNA in human cancer tissues with clearly better precision than both standard EXPAR and RT-qPCR. Asymmetric EXPAR is expected to have an important impact on the development of simple and rapid molecular diagnostic applications for short oligonucleotides.

miR-517a is an independent prognostic marker and contributes to cell migration and invasion in human colorectal cancer

Colorectal cancer (CRC) is a highly invasive tumor that is frequently associated with distant metastasis, which is the primary cause of poor prognosis. However, the mechanisms of metastasis remain poorly understood. MicroRNAs (miRNAs/miRs) have been considered to be implicated in CRC progression. In particular, miR-517a is proposed as a novel tumor-associated miRNA and has a potential role in tumor metastasis. The expression of miR-517a in CRC specimens was detected by reverse transcription-quantitative polymerase chain reaction. Transwell assays were performed to determine the migration and invasion of CRC cells. The putative target genes of miR-517a were disclosed using publicly available databases and western blot analysis. The present study identified that the expression of miR-517a was significantly higher in CRC tissues as compared with adjacent non-tumor tissues. Clinical analysis indicated that increased expression of miR-517a was correlated with poor prognostic features and poor long-term survival of CRC patients. In vitro evidences demonstrated that downregulation of miR-517a inhibited cell migration and invasion in HCT-116 cells. By contrast, upregulation of miR-517a increased the number of migrated and invaded SW480 cells. Notably, miR-517a expression was inversely regulated by forkhead box J3 (FOXJ3) abundance in CRC cells. Furthermore, an inverse correlation between miR-517a and FOXJ3 expression was observed in CRC tissues. In conclusion, miR-517a appears to be an independent prognostic marker for predicting survival of CRC patients, and may promote cell migration and invasion by inhibiting FOXJ3.

Molecular biomarkers in colorectal carcinoma

Colorectal cancer is a tumor with increasing incidence which represents one of the first leading causes of death worldwide. Gene alterations described for colorectal cancer include genome instability (microsatellite and chromosomal instability), CpG islands methylator phenotype, microRNA, histone modification, protein biomarkers, gene mutations (RAS, BRAF, PI3K, TP53, PTEN) and polymorphisms (APC, CTNNB1, DCC). In this article, biomarkers with prognostic value commonly found in colorectal cancer will be reviewed.

MicroRNA-101 down-regulates sphingosine kinase 1 in colorectal cancer cells

MicroRNAs (miRs) dysregulation is a general feature of colorectal cancer (CRC) and other solid tumors, and is associated cancer progression. In the current study, we demonstrate that microRNA-101 (miR-101) inhibits CRC cells probably through down-regulating sphingosine kinase 1 (SphK1). Our results showed that exogenously expressing miR-101 inhibited CRC cell (HT-29 and HCT-116 lines) growth in vitro. At the molecular level, miR-101 dramatically down-regulated SphK1 mRNA and protein expression, causing pro-apoptotic ceramide production in above CRC cells. On the other hand, inhibition of miR-101 through expressing antagomiR-101 increased SphK1 expression to down-regulate ceramide level in HT-29 cells. miR-101 expression increased the in vitro anti-CRC activity of conventional chemo-agents: paclitaxel and doxorubicin. CRC cells with SphK1-shRNA knockdown showed similar phenotypes as the miR-101-expressed CRC cells, presenting with elevated level of ceramide and high sensitivity to paclitaxel or doxorubicin. In vivo, HCT-116 xenograft growth in severe combined immuno-deficient (SCID) mice was dramatically inhibited by over-expressing miR-101. Further, miR-101 enhanced paclitaxel-induced anti-HCT-116 activity in vivo. Together, these results indicate that miR-101 exerts its anti-CRC activities probably through down-regulating SphK1.

MicroRNAs as Regulator of Signaling Networks in Metastatic Colon Cancer

MicroRNAs (miRNAs) are a class of small, noncoding RNA molecules capable of regulating gene expression translationally and/or transcriptionally. A large number of evidence have demonstrated that miRNAs have a functional role in both physiological and pathological processes by regulating the expression of their target genes. Recently, the functionalities of miRNAs in the initiation, progression, angiogenesis, metastasis, and chemoresistance of tumors have gained increasing attentions. Particularly, the alteration of miRNA profiles has been correlated with the transformation and metastasis of various cancers, including colon cancer. This paper reports the latest findings on miRNAs involved in different signaling networks leading to colon cancer metastasis, mainly focusing on miRNA profiling and their roles in PTEN/PI3K, EGFR, TGFβ, and p53 signaling pathways of metastatic colon cancer. The potential of miRNAs used as biomarkers in the diagnosis, prognosis, and therapeutic targets in colon cancer is also discussed.

MicroRNA-153 acts as a prognostic marker in gastric cancer and its role in cell migration and invasion

MicroRNA (miRNA)-153 (miR-153) has been considered as a novel tumor-related miRNA and is found to be significantly deregulated in human cancers. In this study, we found that the expression levels of miR-153 were obviously lower in gastric cancer tissues than those in matched adjacent nontumor tissues. Otherwise, miR-153 was expressed at significantly lower levels in aggressive tumor tissues. Clinical association analysis indicated that low expression of miR-153 was prominently correlated with poor prognostic features in gastric cancer. Furthermore, we demonstrated that the low expression of miR-153 was correlated with short 5-year survival of gastric cancer patients. Multivariate Cox regression analysis indicated that miR-153 was an independent prognostic marker in gastric cancer. Our in vitro studies showed that upregulation of miR-153 reduced cell migration and invasion in MKN-45 cells. Meanwhile, downregulation of miR-153 promoted SGC-7901 cell migration and invasion. An inverse correlation between miR-153 and SNAI1 expression was observed in gastric cancer tissues. In addition, upregulation of miR-153 reduced SNAI1 expression and subsequently suppressed epithelial–mesenchymal transition (EMT) with elevated expression of E-cadherin and reduced expression of vimentin in MKN-45 cells. Furthermore, downregulation of miR-153 increased SNAI1 expression and promoted EMT in SGC-7901 cells. In conclusion, miR-153 is an independent prognostic marker for predicting survival of gastric cancer patients and may promote gastric cancer cell migration and invasion, by inhibiting SNAI1-induced EMT.

microRNAs and Colorectal Cancer

Colorectal cancer (CRC) is one of the most common types of human cancer with high cancer-related morbidity and mortality rates. The development and clinical validation of novel therapeutic avenues have improved the clinical outcome, but metastatic CRC still remains an incurable disease in most cases. The interest in discovering novel pathophysiological drivers in CRC is intensively ongoing and the search for novel biomarkers for early diagnosis, for patient's stratification for prognostic purposes or for predicting treatment response are warranted. microRNAs are small RNA molecules that regulate the expression of larger messenger RNA species by different mechanisms with the final consequence to provide a fine tuning tool for global gene expression patterns. First discovered in worms, around 15 years ago it became clear that microRNAs are also existing in humans and that they are widely involved in human carcinogenesis. Within the last years, tremendous progress in the understanding of microRNAs and their role in CRC carcinogenesis has been developed. In this book chapter, several examples of previously identified microRNAs and how they influence colorectal carcinogenesis will be discussed. The information starting at the underlying molecular mechanisms towards clinical applications will be depicted and an overview what great potential these small molecules might carry in future colorectal cancer medicine, will be discussed.