Induction of epithelial-mesenchymal transition and down-regulation of miR-200c and miR-141 in oxaliplatin-resistant colorectal cancer cells

RNA biomarkers in cancer therapeutics: The promise of personalized oncology

Cancer therapy is a rapidly evolving and constantly expanding field. Current approaches include surgery, conventional chemotherapy and novel biologic agents as in immunotherapy, that together compose a wide armamentarium. The plethora of choices can, however, be clinically challenging in prescribing the most suitable treatment for any given patient. Fortunately, biomarkers can greatly facilitate the most appropriate selection. In recent years, RNA-based biomarkers have proven most promising. These molecules that range from small noncoding RNAs to protein coding gene transcripts can be valuable in cancer management and especially in cancer therapeutics. Compared to their DNA counterparts which are stable throughout treatment, RNA-biomarkers are dynamic. This allows prediction of success prior to treatment start and can identify alterations in expression that could reflect response. Moreover, improved nucleic acid technology allows RNA to be extracted from practically every biofluid/matrix and evaluated with exceedingly high analytic sensitivity. In addition, samples are largely obtained by minimally invasive procedures and as such can be used serially to assess treatment response real-time. This chapter provides the reader insight on currently known RNA biomarkers, the latest research employing Artificial Intelligence in the identification of such molecules and in clinical decisions driving forward the era of personalized oncology.

Interactions between circRNAs and miR-141 in Cancer: From Pathogenesis to Diagnosis and Therapy

The function of non-coding RNAs (ncRNAs) in the pathogenesis and development of cancer is indisputable. Molecular mechanisms underlying carcinogenesis involve the aberrant expression of ncRNAs, including circular RNAs (circRNAs), and microRNAs (miRNAs). CircRNAs are a class of single-stranded, covalently closed RNAs responsible for maintaining cellular homeostasis through their diverse functions. As a part of the competing endogenous RNA (ceRNAs) network, they play a central role in the regulation of accessibility of miRNAs to their mRNA targets. The interplay between these molecular players is based on the primary role of circRNAs that act as miRNAs sponges, and the circRNA/miRNA imbalance plays a central role in different pathologies including cancer. Herein, we present the latest state of knowledge about interactions between circRNAs and miR-141, a well-known member of the miR-200 family, in malignant transformation, with emphasis on the biological role of circRNA/miR-141/mRNA networks as a future target for novel anti-cancer therapies.

MicroRNAs as Predictive Biomarkers in Patients with Colorectal Cancer Receiving Chemotherapy or Chemoradiotherapy: A Narrative Literature Review

Colorectal cancer (CRC) is one of the most common malignancies and is associated with high mortality rates worldwide. The underlying mechanism of tumorigenesis in CRC is complex, involving genetic, lifestyle-related, and environmental factors. Although radical resection with adjuvant FOLFOX (5-fluorouracil, leucovorin, and oxaliplatin) chemotherapy and neoadjuvant chemoradiotherapy have remained mainstays of treatment for patients with stage III CRC and locally advanced rectal cancer, respectively, the oncological outcomes of these treatments are often unsatisfactory. To improve patients' chances of survival, researchers are actively searching for new biomarkers to facilitate the development of more effective treatment strategies for CRC and metastatic CRC (mCRC). MicroRNAs (miRs), small, single-stranded, noncoding RNAs, can post-transcriptionally regulate mRNA translation and trigger mRNA degradation. Recent studies have documented aberrant miR levels in patients with CRC or mCRC, and some miRs are reportedly associated with chemoresistance or radioresistance in CRC. Herein, we present a narrative review of the literature on the roles of oncogenic miRs (oncomiRs) and tumor suppressor miRs (anti-oncomiRs), some of which can be used to predict the responses of patients with CRC to chemotherapy or chemoradiotherapy. Moreover, miRs may serve as potential therapeutic targets because their functions can be manipulated using synthetic antagonists and miR mimics.

FOLFOXIRI Resistance Induction and Characterization in Human Colorectal Cancer Cells

FOLFOXIRI, i.e., the combination of folinic acid, 5-fluorouracil, oxaliplatin, and irinotecan, is a first-line treatment for colorectal carcinoma (CRC), yet non-personalized and aggressive. In this study, to mimic the clinical situation of patients diagnosed with advanced CRC and exposed to a chronic treatment with FOLFOXIRI, we have generated the CRC cell clones chronically treated with FOLFOXIRI. A significant loss in sensitivity to FOLFOXIRI was obtained in all four cell lines, compared to their treatment-naïve calls, as shown in 2D cultures and heterotypic 3D co-cultures. Acquired drug resistance induction was observed through morphometric changes in terms of the organization of the actin filament. Bulk RNA sequencing revealed important upregulation of glucose transporter family 5 (GLUT5) in SW620 resistant cell line, while in the LS174T-resistant cell line, a significant downregulation of protein tyrosine phosphatase receptor S (PTPRS) and oxoglutarate dehydrogenase-like gene (OGDHL). This acquired resistance to FOLFOXIRI was overcome with optimized low-dose synergistic drug combinations (ODCs) acting via the Ras-Raf-MEK-ERK pathway. The ODCs inhibited the cell metabolic activity in SW620 and LS174T 3Dcc, respectively by up to 82%.

The Role and Interactions of Programmed Cell Death 4 and its Regulation by microRNA in Transformed Cells of the Gastrointestinal Tract

Data from GLOBOCAN 2020 estimates that there were 19.3 million new cases of cancer and 10.0 million cancer-related deaths in 2020 and that this is predicted to increase by 47% in 2040. The combined burden of cancers of the gastrointestinal (GI) tract, including oesophageal-, gastric- and colorectal cancers, resulted in 22.6% of the cancer-related deaths in 2020 and 18.7% of new diagnosed cases. Understanding the aetiology of GI tract cancers should have a major impact on future therapies and lessen this substantial burden of disease. Many cancers of the GI tract have suppression of the tumour suppressor Programmed Cell Death 4 (PDCD4) and this has been linked to the expression of microRNAs which bind to the untranslated region of PDCD4 mRNA and either inhibit translation or target the mRNA for degradation. This review highlights the properties of PDCD4 and documents the evidence for the regulation of PDCD4 expression by microRNAs in cancers of the GI tract.

Tumor-Originated Exosomal hsa-miR-3937 as a Minimally Invasive Early Biomarker for Liquid Biopsy of Colorectal Cancer

Background

Exosomal microRNAs (miRNAs) have been linked to the genesis and progression of certain cancers. The role and regulation mechanism of cancer-derived exosomal miRNAs in CRC, however, remain unknown.

Methods

To address this, we first used miRNA sequencing to describe the miRNA profiles of circulating exosomes in order to identify miRNAs that were differently expressed between patients with CRC and healthy controls. Transmission electron microscopy, nanoparticle tracking analysis (NTA), and western blot were used to analyze exosomes generated from CRC cells. CCK-8, wound healing, and Transwell tests were used to see whether exosomes affected CRC cell proliferation, metastasis, and apoptosis, respectively. We chose and identified hsa-miR-3937, which was abundant in tumor-generated exosomes, based on earlier RNA sequencing data of exosomes obtained and extracted from seven matched specimens of tumor tissues and surrounding normal tissues of CRC patients.

Results

The role of hsa-miR-3937 in CRC cells was found, and silencing of hsa-miR-3937 decreased CRC cell invasion and migration in a Transwell experiment. Furthermore, we discovered that there was no link between hsa-miR-3937 expression and CRC cell apoptosis. Initially, it was discovered that BCL2L12 was the target gene of hsa-miR-3937, and the TCGA database highlighted the potential therapeutic relevance of BCL2L12. Furthermore, to identify hsa-miR-3937 as a biomarker of CRC, we used peripheral blood samples rather than patient tissues and extracted exosomes from plasma samples. To assess the expression levels and predictive usefulness of plasma exosomal hsa-miR-3937 in CRC, we performed RT-qPCR to identify hsa-miR-3937 levels in all samples. We also gathered clinicopathological information in order to look for links between aberrant hsa-miR-3937 expression and clinicopathological characteristics. The pathologic stage of CRC patients was linked to hsa-miR-3937 expression levels, and the same was true for the T stage. ROC curve study revealed that hsa-miR-3937 outperforms CEA and CA199. The combination of hsa-miR-3937, CEA, and CA199 exhibited the highest sensitivity for CRC diagnosis.

Conclusions

Our findings show that the tumor-originated exosomal hsa-miR-3937 is a potential and effective liquid biopsy marker for colorectal cancer detection and therapy.

MicroRNAs and drug resistance in colorectal cancer with special focus on 5-fluorouracil

Colorectal cancer is globally one of the most common cancers in all age groups. The current chemotherapy combinations for colorectal cancer treatment include 5-fluorouracil-based regimens; however, drug resistance remains one of the main reasons for chemotherapy failure and disease recurrence. Many studies have determined colorectal cancer chemoresistance mechanisms such as drug efflux, cell cycle arrest, DNA damage repair, apoptosis, autophagy, vital enzymes, epigenetic, epithelial-mesenchymal transition, stem cells, and immune system suppression. Several microRNAs affect drug resistance by regulating the drug resistance-related target genes in colorectal cancer. These drug resistance-related miRNAs may be used as promising biomarkers for predicting drug response or as potential therapeutic targets for treating patients with colorectal cancer. This work reviews and discuss the role of selected microRNAs in 5-fluorouracil resistance and their molecular mechanisms in colorectal cancer.

Comprehensive analysis of ceRNA network of ERCC4 in colorectal cancer

Objective

ERCC4 is one of the most significant molecules of Nucleotide Excision Repair (NER), which has been researched due to its high expression in colorectal cancer (CRC). This study aimed to find out the ceRNA (competitive endogenous RNA) network of ERCC4 in CRC.

Methods and Materials

Pan cancer mRNA expression of ERCC4 was evaluated using TCGA database. The protein expression of ERCC4 was evaluated based on the Human Protein Atlas (HPA). We screened DElncRNAs and DEmiRNAs in two groups of ERCC4^high and ERCC4^low expression in CRC. Then a lncRNA-miRNA-ERCC4 regulatory network was constructed based on DElncRNAs and DEmiRNAs using Starbase database and visualized by Cytoscape software. Kaplan-Meier analysis was performed to evaluate the prognostic value of the ceRNA network. Further, RT-PCR was performed to validate the expression of the representative molecules in the ceRNA network in CRC and normal tissues. The relationship between drug sensitivity and these molecules were also evaluated using RNAactDrug database.

Results

ERCC4 was overexpressed in a variety of tumors at mRNA levels, including CRC. High expression of ERCC4 was also observed on protein level in CRC. A total of 1,885 DElncRNAs and 68 DEmiRNAs were identified from CRC samples in ERCC4^high and ERCC4^low expression groups. Predicted by the Starbase database, we got interacting miRNAs and lncRNAs of ERCC4 from the DEmiRNAs and DElncRNAs, and a lncRNA-miRNA-ERCC4 regulatory network was constructed. Kaplan-Meier survival curves results showed that miR-200c-3p (hazard ratio [HR] = 0.62, P = 0.032), MALAT1 (HR = 1.54, P = 0.016), and AC005520.2 (hazard ratio [HR] = 1.75, P = 0.002) were significantly associated with the prognosis of CRC. After validation by RT-PCR, we found that ERCC4 and MALAT1 were up-regulated in CRC compared with normal tissues, while miR-200c-3p was down-regulated. A strong negative correlation was observed between MALAT1 and miR-200c-3p. Drug sensitivity analysis showed that ERCC4, miR-200c and MALAT1 were all associated with Cisplatin.

Conclusion

We constructed a ceRNA network of ERCC4 in CRC, of which the MALAT1-miR-200c-3p-ERCC4 axis may be involved in the development, prognosis and chemotherapy sensitivity of CRC. These findings might provide novel clues and insights on the molecular mechanisms of ERCC4 and NER pathway in CRC.

Oxaliplatin resistance in colorectal cancer enhances TRAIL sensitivity via death receptor 4 upregulation and lipid raft localization

Colorectal cancer (CRC) remains a leading cause of cancer death, and its mortality is associated with metastasis and chemoresistance. We demonstrate that oxaliplatin-resistant CRC cells are sensitized to TRAIL-mediated apoptosis. Oxaliplatin-resistant cells exhibited transcriptional downregulation of caspase-10, but this had minimal effects on TRAIL sensitivity following CRISPR-Cas9 deletion of caspase-10 in parental cells. Sensitization effects in oxaliplatin-resistant cells were found to be a result of increased DR4, as well as significantly enhanced DR4 palmitoylation and translocation into lipid rafts. Raft perturbation via nystatin and resveratrol significantly altered DR4/raft colocalization and TRAIL sensitivity. Blood samples from metastatic CRC patients were treated with TRAIL liposomes, and a 57% reduction of viable circulating tumor cells (CTCs) was observed. Increased DR4/lipid raft colocalization in CTCs was found to correspond with increased oxaliplatin resistance and increased efficacy of TRAIL liposomes. To our knowledge, this is the first study to investigate the role of lipid rafts in primary CTCs.

Silencing of E-cadherin expression leads to increased chemosensitivity to irinotecan and oxaliplatin in colorectal cancer cell lines

Colorectal carcinoma (CRC) is a leading malignant disease in most developed countries. In advanced stages it presents with metastatic dissemination and significant chemoresistance. Despite intensive studies, no convincing evidence has been published concerning the association of cadherins and epithelial-mesenchymal transition (EMT) as a direct cause of acquired chemoresistance in CRC. The present study was designed to investigate the role of E-cadherin in EMT and its associated chemosensitivity/chemoresistance in four immortalized CRC cell lines representing various stages of CRC development (i.e. HT29 and Caco-2-early, SW480 and SW620 late). The expression of E-cadherin gene CDH1 was downregulated by the specific siRNA. Cell proliferation and chemosensitivity to irinotecan (IT) and oxaliplatin (OPT) were detected using WST-1 and x-CELLigence Real Time analysis. Expression of selected EMT markers were tested and compared using RT-PCR and western blot analysis in both variants (E-cadherin silenced and non-silenced) of each cell line. We have discovered that downregulation of E-cadherin expression has a diverse effect on both cell proliferation as well as the expression of EMT markers in individual tested CRC cell lines, with Caco-2 cells being the most responsive. On the other hand, reduced E-cadherin expression resulted in increased sensitivity of all cell lines to IT and mostly to OPT which might be related to changes in intracellular metabolism of these drugs. These results suggest dichotomy of E-cadherin involvement in the phenotypic EMT spectrum of CRC and warrants further mechanistic studies.

MicroRNA-200c Prevents Progress of Cutaneous Squamous Cell Carcinoma by Targeting Tyrosine-Protein Kinase Fyn (FYN)

Cutaneous squamous cell carcinoma (cSCC), a malignant skin tumor, begins in the epidermis and the keratinocytes of the skin appendages. However, the cause remains unclear. MicroRNA-200c (miR-200c), a key modulator of epithelial-to-mesenchymal transition (EMT), has been reported to act as an anticancer gene in a variety of cancers. However, its role and partial mechanism in cSCC remain undetermined. The results of this study showed depleted levels of miR-200c in cSCC tissues. Its suppressive effects on cell proliferation, and motility, as well as its apoptosis-promoting effect, were observed in the A-431 cells. Additionally, immunofluorescence and qRT-PCR assays revealed that FYN acted as a direct target of miR-200c, and FYN knockdown exerted had similar impact as that of miR-200c overexpression, including increased cellular apoptosis and decreased cellular growth. These results emphasized the onco-suppressive nature of miR-200c, which was evident based on its interaction with FYN in cSCC. This finding could have potential benefits in developing cSCC therapy.

miR-33a-5p in small extracellular vesicles as non-invasive biomarker for oxaliplatin sensitivity in human colorectal cancer cells

microRNAs (miRNAs) contained in small extracellular vesicles (sEVs) are candidates for non-invasive biomarkers. Oxaliplatin (L-OHP) has been approved for advanced colorectal cancer (CRC) chemotherapy. However, the response to L-OHP differs among CRC patients. In addition, CRC cells often acquire the resistance to L-OHP. This study aimed at the prediction of L-OHP sensitivity by measuring extracellular miRNAs levels. Firstly, we compared intracellular miRNAs expressions in L-OHP-sensitive CRC cells (SW620 and HCT116 cells) with those in acquired and intrinsic L-OHP-resistant cells. In microarray and real-time RT-PCR analyses, the intracellular miR-33a-5p, miR-210–3p, and miR-224–5p expressions were lower in acquired and intrinsic L-OHP-resistant CRC cells than sensitive cells. Furthermore, in SW620 cells, L-OHP sensitivity was decreased by miR-33a-5p inhibitor. On the other hand, miR-210–3p or miR-224–5p inhibitor did not affect L-OHP sensitivity in SW620 cells. Secondly, the amount of miR-33a-5p, miR-210–3p, and miR-224–5p in sEVs was compared. The amount of miR-33a-5p and miR-210–3p in sEVs secreted from acquired and intrinsic L-OHP-resistant cells tended to be small. miR-224–5p was not detected in sEVs secreted from three types of CRC cells examined. To the best of our knowledge, this is the first study demonstrating that miR-33a-5p and/or miR-210–3p in sEVs would be candidates for biomarkers of L-OHP sensitivity. In particular, miR-33a-5p is a promising candidate because it would be directly involved in L-OHP sensitivity.

•

miR-33a-5p was down-regulated in oxaliplatin-resistant colorectal cancer cells.

•

Reduction of intracellular miR-33a-5p expression caused oxaliplatin resistance.

•

miR-33a-5p amount in small extracellular vesicles from resistant cells was small.

•

miR-33a-5p is a candidate for non-invasive biomarker of oxaliplatin sensitivity.

Molecular mechanisms and clinical implications of miRNAs in drug resistance of colorectal cancer

Systemic chemotherapy is identified as a curative approach to prolong the survival time of patients with colorectal cancer (CRC). Although great progress in therapeutic approaches has been achieved during the last decades, drug resistance still extensively persists and serves as a major hurdle to effective anticancer therapy for CRC. The mechanism of multidrug resistance remains unclear. Recently, mounting evidence suggests that a great number of microRNAs (miRNAs) may contribute to drug resistance in CRC. Certain of these miRNAs may thus be used as promising biomarkers for predicting drug response to chemotherapy or serve as potential targets to develop personalized therapy for patients with CRC. This review mainly summarizes recent advances in miRNAs and the molecular mechanisms underlying miRNA-mediated chemoresistance in CRC. We also discuss the potential role of drug resistance-related miRNAs as potential biomarkers (diagnostic and prognostic value) and envisage the future orientation and challenges in translating the findings on miRNA-mediated chemoresistance of CRC into clinical applications.

Long non-coding RNA (lncRNA) and epithelial-mesenchymal transition (EMT) in colorectal cancer: a systematic review

BACKGROUND

Colorectal cancer (CRC) is a leading cause of cancer-related death. Epithelial-mesenchymal transition (EMT) is a major process in tumor metastasis development. This systematic review aims to describe the role of long non-coding RNA (lncRNA) in EMT in CRC.

METHODS

The electronic databases, PubMed, Cochrane, and EMBASE, were searched from January1990 to June 2019 to identify studies examining lncRNA and their role in mediating EMT in CRC. Studies examining clinical specimens and/or in vitro experiments were included.

RESULTS

In 61 identified studies, 54 lncRNAs were increased in CRC compared to normal colorectal epithelium. Increased lncRNA expression was frequently associated with worse survival. Many lncRNAs mediate their effect through competitive endogenous RNA or transcription factor regulation. The ZEB1, 2/E-cadherin, Wnt/β-catenin signaling, and chromatin remodeling pathways are discussed in particular.

CONCLUSIONS

lncRNAs are major regulators of EMT and predictor adverse outcome in CRC patients. Future research must focus on delineating lncRNA function prior to potential clinical use.

The function of miR-200 family in oxidative stress response evoked in cancer chemotherapy and radiotherapy

Since the beginning of the discovery of microRNAs (miRs), these molecules have attracted highly progressive attention due to their powerful regulatory roles in a broad spectrum of biological processes, including proliferation, differentiation, apoptosis and carcinogenesis. With regard to carcinogenesis, the miRs regulatory potency has been associated with cancer onset, progression, metastasis, diagnosis and therapeutic response. In this review we discuss the impact of miR-200 family on drug resistance development during anti-cancer therapy. Developing resistance to chemotherapeutic drugs as well as radiotherapy are major clinical obstacles in the successful therapeutic strategies to cancer treatment. Acquired cancer chemoresistance is a multifactorial phenomenon involving such factors as tumor type, tumor stage, cellular reactive oxygen species (ROS) level or ROS-responsive miRs profile. ROS level could influence the miRs expression level, which changes the cellular profile of the content of miRs. Such significant changes in the cellular miRs profile generate subsequent biological effects through the regulation of their target genes. This review outlines the interactions between ROS and miR-200 family in different kinds of cancers in response to chemotherapy.

Oxaliplatin resistance is enhanced by saracatinib via upregulation Wnt-ABCG1 signaling in hepatocellular carcinoma

BACKGROUND

Chemo-resistance in hepatocellular carcinoma (HCC) is a major problem, and acquired drug resistance prevents cancer therapies from achieving complete responses. Molecular targeting therapy presents an opportunity to impede tumor through combination or sequential therapy, while the accurate effect is vague.

METHODS

The efficacy of combinations between oxaliplatin and anti-cancer molecular targeting drugs was screened. Strangely, the combined chemotherapy with oxaliplatin and saracatinib induced significantly antagonistic effects. Then the antitumor effects of combined treatment with saracatinib and oxaliplatin were confirmed in wide type HCC as well as in saracatinib- and oxaliplatin-resistant HCC. RNA sequencing was used to explore the resistance mechanism, and the roles of ATP-binding cassette transporter G1 (ABCG1) and Wnt signaling in oxaliplatin resistance were confirmed.

RESULTS

Chemotherapy with oxaliplatin and saracatinib individually induced strong anti-HCC effects, while combined or sequential treatment of HCC cells with these two drugs exhibited reduced efficacy compared to treatment with the single drugs. And it was saracatinib treatment caused oxaliplatin resistance. RNA sequencing revealed 458 genes that were altered by treatment with saracatinib and oxaliplatin. Of these, the gene encoding ABCG1 and Wnt-associated genes were significantly upregulated. Upregulation of ABCG1 and oxaliplatin resistance were associated with activation of Wnt signaling. Interference with ABCG1 expression or inhibition of Wnt signaling resulted in reversal of the saracatinib-induced oxaliplatin resistance in HCC.

CONCLUSIONS

These studies demonstrated that combined or sequential chemotherapy with oxaliplatin and saracatinib reduced antitumor efficacy, and this antagonism was attributed to the activation of Wnt signaling and upregulation of ABCG1 by saracatinib.

miR-200 affects tamoxifen resistance in breast cancer cells through regulation of MYB

Resistance to tamoxifen is a major clinical challenge. Research in recent years has identified epigenetic changes as mediated by dysregulated miRNAs that can possibly play a role in resistance to tamoxifen in breast cancer patients expressing estrogen receptor (ER). We report here elevated levels of EMT markers (vimentin and ZEB1/2) and reduced levels of EMT-regulating miR-200 (miR-200b and miR-200c) in ER-positive breast cancer cells, MCF-7, that were resistant to tamoxifen, in contrast with the naïve parental MCF-7 cells that were sensitive to tamoxifen. Further, we established regulation of c-MYB by miR-200 in our experimental model. C-MYB was up-regulated in tamoxifen resistant cells and its silencing significantly decreased resistance to tamoxifen and the EMT markers. Forced over-expression of miR-200b/c reduced c-MYB whereas reduced expression of miR-200b/c resulted in increased c-MYB We further confirmed the results in other ER-positive breast cancer cells T47D cells where forced over-expression of c-MYB resulted in induction of EMT and significantly increased resistance to tamoxifen. Thus, we identify a novel mechanism of tamoxifen resistance in breast tumor microenvironment that involves miR-200-MYB signaling.

pH-Responsive PEG-Shedding and Targeting Peptide-Modified Nanoparticles for Dual-Delivery of Irinotecan and microRNA to Enhance Tumor-Specific Therapy

Irinotecan is one of the main chemotherapeutic agents for colorectal cancer (CRC). MicroRNA-200 (miR-200) has been reported to inhibit metastasis in cancer cells. Herein, pH-sensitive and peptide-modified liposomes and solid lipid nanoparticles (SLN) are designed for encapsulation of irinotecan and miR-200, respectively. These peptides include one cell-penetrating peptide, one ligand targeted to tumor neovasculature undergoing angiogenesis, and one mitochondria-targeting peptide. The peptide-modified nanoparticles are further coated with a pH-sensitive PEG-lipid derivative with an imine bond. These specially-designed nanoparticles exhibit pH-responsive release, internalization, and intracellular distribution in acidic pH of colon cancer HCT116 cells. These nanoparticles display low toxicity to blood and noncancerous intestinal cells. Delivery of miR-200 by SLN further increases the cytotoxicity of irinotecan-loaded liposomes against CRC cells by triggering apoptosis and suppressing RAS/β-catenin/ZEB/multiple drug resistance (MDR) pathways. Using CRC-bearing mice, the in vivo results further indicate that irinotecan and miR-200 in pH-responsive targeting nanoparticles exhibit positive therapeutic outcomes by inhibiting colorectal tumor growth and reducing systemic toxicity. Overall, successful delivery of miR and chemotherapy by multifunctional nanoparticles may modulate β-catenin/MDR/apoptosis/metastasis signaling pathways and induce programmed cancer cell death. Thus, these pH-responsive targeting nanoparticles may provide a potential regimen for effective treatment of colorectal cancer.

MicroRNAs as potential therapeutic targets to predict responses to oxaliplatin in colorectal cancer: From basic evidence to therapeutic implication

Colorectal cancer (CRC) is one of the most common malignancies with poor prognosis. Oxaliplatin-based chemotherapy is an important treatment for CRC; however, the cells develop resistance to therapy. The mechanisms underlying oxaliplatin resistance are complex and unclear. There is increasing evidence that microRNAs (miRNAs) (i.e., miR-34a, miR-143, miR-153, miR-27a, miR-218, and miR-520) play an essential role in tumorigenesis and chemotherapy resistance, by targeting various cellular and molecular pathways (i.e., PI3K/Akt/Wnt, EMT, p53, p21, and ATM) that are involved in the pathogenesis of CRC. Identifying the miRNAs that are involved in chemo-resistance, and their function, may help as a potential therapeutic option for treatment of CRC or as potential prognostic biomarker. Here, we summarized the clinical impact of miRNAs that have critical roles in the development of resistance to oxaliplatin in CRC.

Crosstalk between autophagy and epithelial-mesenchymal transition and its application in cancer therapy

Autophagy is a highly conserved catabolic process that mediates degradation of pernicious or dysfunctional cellular components, such as invasive pathogens, senescent proteins, and organelles. It can promote or suppress tumor development, so it is a “double-edged sword” in tumors that depends on the cell and tissue types and the stages of tumor. The epithelial-mesenchymal transition (EMT) is a complex biological trans-differentiation process that allows epithelial cells to transiently obtain mesenchymal features, including motility and metastatic potential. EMT is considered as an important contributor to the invasion and metastasis of cancers. Thus, clarifying the crosstalk between autophagy and EMT will provide novel targets for cancer therapy. It was reported that EMT-related signal pathways have an impact on autophagy; conversely, autophagy activation can suppress or strengthen EMT by regulating various signaling pathways. On one hand, autophagy activation provides energy and basic nutrients for EMT during metastatic spreading, which assists cells to survive in stressful environmental and intracellular conditions. On the other hand, autophagy, acting as a cancer-suppressive function, is inclined to hinder metastasis by selectively down-regulating critical transcription factors of EMT in the early phases. Therefore, the inhibition of EMT by autophagy inhibitors or activators might be a novel strategy that provides thought and enlightenment for the treatment of cancer. In this article, we discuss in detail the role of autophagy and EMT in the development of cancers, the regulatory mechanisms between autophagy and EMT, the effects of autophagy inhibition or activation on EMT, and the potential applications in anticancer therapy.

MicroRNA-552 deficiency mediates 5-fluorouracil resistance by targeting SMAD2 signaling in DNA-mismatch-repair-deficient colorectal cancer

OBJECTIVE

Although DNA-mismatch-repair-deficient (dMMR) status and aberrant expression of miRNAs are both critically implicated in the pathogenesis of resistance to 5-fluorouracil (5-FU) in colorectal cancer (CRC), whether these two factors regulate tumor response to 5-FU in a coordinated manner remains unknown. This study is designed to elucidate whether changes in miR-552 expression levels correlate to 5-FU-based chemoresistance in CRC, and to further identify the putative targets of miR-552 using multiple approaches.

METHODS

miR-552 expression was assessed in 5-FU-resistant CRC tissues and cells using real-time PCR. Effects of miR-552 dysregulation on 5-FU resistance in CRC cells were determined by measuring cell viability, apoptosis and in vivo oncogenic capacity. Finally, we studied the posttranscriptional regulation of SMAD2 by miR-552 using multiple approaches including luciferase reporter assay, site-directed mutagenesis and transient/stable transfection, at molecular and functional levels.

RESULTS

Expression of miR-552 was significantly downregulated in 5-FU-resistant CRC tissues and cells, and this downregulation, regulated by dMMR, was associated with poor postchemotherapy prognosis. Functionally, forced expression of miR-552 exhibited a proapoptotic effect and attenuated 5-FU resistance, whereas inhibition of miR-552 expression potentiated 5-FU resistance in CRC cells. Mechanically, miR-552 directly targeted the 3'-UTR of SMAD2, and stable ablation of SMAD2 neutralized the promoting effects of miR-552 deficiency-induced 5-FU resistance.

CONCLUSIONS

Overall, our findings have revealed a critical role of miR-552/SMAD2 cascade in modulating cellular response to 5-FU chemotherapy. miR-552 may act as an efficient mechanistic link synchronizing dMMR and 5-FU resistance in CRC.

The Developing Story of Predictive Biomarkers in Colorectal Cancer

Colorectal cancer (CRC) is the third most common malignancy worldwide. Surgery remains the most important treatment for non-metastatic CRC, and the administration of adjuvant chemotherapy depends mainly on the disease stage, which is still the strongest prognostic factor. A refined understanding of the genomics of CRC has recently been achieved thanks to the widespread use of next generation sequencing with potential future therapeutic implications. Microsatellite instability (MSI) has been suggested as a predictive marker for response to anti-programmed-cell-death protein 1 (PD-1) therapy in solid tumors, including CRC. It should be noted that not all cancers with MSI phenotype respond to anti-PD-1 immunotherapy, highlighting the urgent need for even better predictive biomarkers. Mitogen-Activated Protein Kinase (MAPK) pathway genes KRAS, NRAS, and BRAF represent important molecular targets and could serve as independent prognostic biomarkers in CRC, and identify those who potentially benefit from anti-epidermal growth factor receptor (EGFR) treatment. Emerging evidence has attributed a significant role to inflammatory markers including blood cell ratios in the prognosis and survival of CRC patients; these biomarkers can be easily assessed in routine blood exams and be used to identify high-risk patients or those more likely to benefit from chemotherapy, targeted therapies and potentially immunotherapy. Analysis of cell-free DNA (cfDNA), circulating tumor cells (CTC) and/or micro RNAs (miRNAs) could provide useful information for the early diagnosis of CRC, the identification of minimal residual disease and, the evaluation of the risk of recurrence in early CRC patients. Even the selection of patients suitable for the new targeted therapy is becoming possible with the use of predictive miRNA biomarkers. Finally, the development of treatment resistance with the emergence of chemo-resistance clones after treatment remains the most important challenge in the clinical practice. In this context it is crucial to identify potential biomarkers and therapeutic targets which could lead to development of new and more effective treatments.

Chemotherapy-induced miR-141/MAP4K4 signaling suppresses progression of colorectal cancer

One of the treatment failures for colorectal cancer (CRC) is resistance to chemotherapy drugs. miRNAs have been demonstrated to be a new regulator of pathobiological processes in various tumors. While few studies have explored the specific role of miR-141 in mediating 5-fluorouracil (5-FU) sensitivity of CRC cells, the present study aimed to detect the contribution of miR-141 in 5-FU sensitivity. The CRC cells viability was measured by MTS assay and cell colony forming. The expression of miR-141 and its downstream targets were assessed by reverse transcription quantitative PCR, Western blotting, and immunohistochemistry. The functional assays were conducted using CRC cells and nude mice. At the present study, we found overexpression of miR-141 could inhibit proliferation, migration, tumor-forming and invasive potential of CRC cells in vitro and mitogen-activated protein kinase kinase kinase kinase 4 (MAP4K4) was verified as a directed target of miR-141 The combination treatment of miR-141 with 5-FU, directly targetting MAP4K4, could better inhibit invasion and metastasis of CRC cells colony than either one alone. Furthermore, overexpression of miR-141, targetting MAP4K4, enhanced the effected of 5-FU and suppressed the malignant biological behaviors, in vivo Our findings showed that 5-FU inhibited malignant behavior of human CRC cells in vitro and in vivo by enhancing the efficiency of miR-141 Our data suggested that targetting the miR-141/MAP4K4 signaling pathway could be a potential molecular target that may enhance chemotherapeutic efficacy in the treatment of CRC.

MiR-141-3p Suppresses Tumor Growth and Metastasis in Papillary Thyroid Cancer via Targeting Yin Yang 1

MicroR-141-3p has been found to be downregulated in papillary thyroid carcinoma (PTC), while little is known about the cellular functions and precise signals elicited by miR-141-3p in PTC. The results of this study indicated that the expression of miR-141-3p was aberrantly down-regulated in PTC tissues and cell lines, compared with the adjacent normal tissues and normal thyroid epithelial cells. Furthermore, the miR-141-3p expression level was negatively associated with TNM stage and lymph node metastasis in PTC. Expression of miR-141-3p effectively inhibited cell growth, promoted apoptosis, and suppressed invasion in PTC cells. Meanwhile, miR-141-3p knockdown with miR-141-3p inhibitor reversed these effects. Consistent with the in vitro study, miR-141-3p also exhibited anti-neoplastic activity in vivo. Moreover, the results revealed that miR-141-3p directly recognized the 3' untranslated region (3'UTR) of Yin Yang 1 (YY1) and negatively regulated the expression of YY1 at both protein and mRNA levels. Ectopic expression of YY1 could effectively abrogate the anti-metastatic and proapoptotic effects of miR-141-3p. In summary, the findings suggested that miR-141-3p can act as a tumor suppressor in PTC and may be a potential therapeutic target for PTC treatment. Anat Rec, 302:258-268, 2019. © 2018 Wiley Periodicals, Inc.

Characterization of microRNA expression in primary human colon adenocarcinoma cells (SW480) and their lymph node metastatic derivatives (SW620)

Background and objective

Metastasis is the major cause of cancer-related deaths in patients with colon cancer, however, the exact molecular mechanism is unclear. MicroRNAs (miRNAs) play an important role in the pathogenesis and progression of cancer. Therefore, in this study, we aimed to identify differentially expressed miRNAs in two colon carcinoma cell lines: SW480, derived from primary colon carcinoma and SW620, derived from lymph node metastasis, which were obtained from the same patient.

Materials and methods

Three independent samples of cancer cells were collected from SW480 and SW620 cells, respectively. An miRNA microarray platform, miRCURY LNA™ microRNA array with 1,223 probes containing 3,000 capture probes, was used to determine the miRNA expression profiles of these two cell lines. Differentially expressed miRNAs were validated by quantitative reverse transcription-polymerase chain reaction (qRT-PCR).

Results

The raw data were submitted to the Gene Expression Omnibus database (GSE72412). Thirteen miRNAs were differentially expressed between SW480 and SW620 cells, of which, seven miRNAs (hsa-miR-920, hsa-miR-636, hsa-miR-766-3p, hsa-miR-545-5p, hsa-miR-195-3p, hsa-miR-125a-3p, and hsa-miR-196b-3p) were found to be upregulated and six miRNAs (hsa-miR-3613-3p, hsa-miR-29b-3p, hsa-miR-1297, hsa-miR-141-5p, hsa-miR-200c-3p, and hsa-miR-141-3p) were found to be downregulated. Target analysis of the predicted miRNAs showed that these genes were primarily involved in protein binding, cell adhesion, and cancer metastasis. Furthermore, qRT-PCR validated the results of miRNA microarray.

Conclusion

This is the first systematic analysis of the differences of miRNAs between SW480 and SW620 cells. The results provide useful information to explore potential biomarkers of miRNAs for predicting colon cancer metastasis.

MicroRNAs in the prognosis and therapy of colorectal cancer: From bench to bedside

MicroRNAs (miRNAs) are small, single-stranded, noncoding RNAs that can post-transcriptionally regulate the expression of various oncogenes and tumor suppressor genes. Dysregulated expression of many miRNAs have been shown to mediate the signaling pathways critical in the multistep carcinogenesis of colorectal cancer (CRC). MiRNAs are stable and protected from RNase-mediated degradation, thereby enabling its detection in biological fluids and archival tissues for biomarker studies. This review focuses on the role and application of miRNAs in the prognosis and therapy of CRC. While stage II CRC is potentially curable by surgical resection, a significant percentage of stage II CRC patients do develop recurrence. MiRNA biomarkers may be used to stratify such high-risk population for adjuvant chemotherapy to provide better prognoses. Growing evidence also suggests that miRNAs are involved in the metastatic process of CRC. Certain of these miRNAs may thus be used as prognostic biomarkers to identify patients more likely to have micro-metastasis, who could be monitored more closely after surgery and/or given more aggressive adjuvant chemotherapy. Intrinsic and acquired resistance to chemotherapy severely hinders successful chemotherapy in CRC treatment. Predictive miRNA biomarkers for response to chemotherapy may identify patients who will benefit the most from a particular regimen and also spare the patients from unnecessary side effects. Selection of patients to receive the new targeted therapy is becoming possible with the use of predictive miRNA biomarkers. Lastly, forced expression of tumor suppressor miRNA or silencing of oncogenic miRNA in tumors by gene therapy can also be adopted to treat CRC alone or in combination with other chemotherapeutic drugs.

The role of Her2-Nrf2 axis in induction of oxaliplatin resistance in colon cancer cells

Nuclear factor erythroid 2-related factor 2 (Nrf2) plays a pivotal role in promoting chemoresistance by regulation of antioxidants and detoxification enzymes. Her2 is a member of tyrosine kinase receptor family with a key function in resistance of cancer cells to chemotherapeutics. The aim of this study was to investigate the possible cross talk between Nrf2 and Her2 mediated signaling pathways in development of oxaliplatin resistance in colon cancer cells. We first generated oxaliplatin-resistant LS174T and SW480 colon cancer cells with different Her2 expression levels by employing IC50 concentrations followed by a resting period. We evaluated the viability and apoptosis of the cells by MTT and flow cytometry assays, respectively. Nrf2 and Her2 gene expression levels were examined by qRT-PCR. The morphology analysis and combination index calculation were performed using the ImagJ and CompuSyn softwares, respectively. Development of resistant cells revealed a marked increase in half maximal inhibitory concentration (IC50) value from 3.95 ± 0.92 μM to 29.27 ± 3.13 μM in SW480 cells and 377 ± 46 nM to 9.59 ± 0.76 μM in LS174T cells with a significant change in morphology of the cells from elongated to small round shape (p < 0.05). Her2 expression level was increased in both types of resistant cells, but the Nrf2 expression was increased in LS174T resistant (LS174T/Res) cells and decreased in SW480/Res cells which were consistent with the level of resistance in these cells (25 fold increase in IC50 value in LS174T/Res cells versus 7 fold increase in this value in SW480/Res cells). Inhibition of either Nrf2 or Her2 alone and in combination caused a significant increase in oxaliplatin-induced cytotoxicity and apoptosis with maximum effects in SW480/Res cells with low Her2 and Nrf2 expression levels. Altogether, our results suggest that inhibition of Nrf2 signaling in colon cancer patients with Her2 overexpression can be considered as an important strategy to overcome oxaliplatin resistance.

USP14 de-ubiquitinates vimentin and miR-320a modulates USP14 and vimentin to contribute to malignancy in gastric cancer cells

Vimentin plays important roles in the epithelial-to-mesenchymal transition (EMT). In this study, we found that vimentin was highly expressed in human gastric cancer (GC) tissues and cell lines and significantly promoted cell growth, migration and invasion. Ubiquitin-specific protease 14 (USP14) interacted with the vimentin protein, which led to its de-ubiquitination. miR-320a was found to bind to the 3′UTR of both vimentin and USP14 transcripts and downregulate the expression of both proteins. The downregulation of miR-320a upregulates vimentin expression by directly binding to the 3′UTR of vimentin to derepress expression and indirectly by augmenting USP14 to increase vimentin stability in GC cells. Taken together, these results provide new insight into malignancy in gastric cancers.

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.

Different Schedule-Dependent Effects of Epigenetic Modifiers on Cytotoxicity by Anticancer Drugs in Colorectal Cancer Cells

Limited information is currently available on how to apply epigenetic modifiers to current colorectal cancer (CRC) chemotherapy. The purpose of this study is to clarify the schedule-dependent effects of combined treatment with conventional anticancer drugs and epigenetic modifiers in human CRC cells. Cytotoxicity in 4 CRC cell lines (SW480, HT29, SW48, and HCT116) was measured using the WST-8 assay. As epigenetic modifiers, 3 DNA methyltransferase (DNMT) inhibitors such as decitabine (DAC), azacytidine (AC), and zebularine (Zeb), and 3 histone deacetylase (HDAC) inhibitors including trichostatin A (TSA), suberoylanilide hydroxamic acid (SAHA), and valproic acid (VPA) were used. Combination effects were analyzed by the isobologram method. SW480 cells showed the lowest sensitivity to the anticancer drugs 5-fluorouracil, SN-38 (the active form of irinotecan), and oxaliplatin. In SW480 cells, epigenetic modifiers other than VPA showed the most significant synergistic effects when used before anticancer drugs, while VPA showed synergistic effects in co- or post-treatment. In the 3 other CRC cells, synergistic effects were less frequent and weaker. The dose of anticancer drugs may be reduced by combining epigenetic modifiers in SW480 cells, which are less sensitive to anticancer drugs, unlike the more sensitive HT29, SW48, and HCT116 cell lines. These results provide useful information for understanding how to incorporate epigenetic modifiers into current CRC chemotherapy.

MicroRNA-141-3p promotes glioma cell growth and temozolomide resistance by directly targeting p53

Glioblastoma multiforme is the most common primary malignancy in the brain and confers a uniformly poor prognosis. MicroRNAs have been shown to activate or inhibit tumorigenesis. Abnormalities in the p53 signaling pathway are found in various cancers and correlate with tumor formation. We examined the expression of microRNA-141-3p (miR-141-3p) in glioma of different grades by analysis of expression profiling databases and clinical specimens. Cell proliferation and flow cytometry assays were performed to evaluate the promotion of miR-141-3p in proliferation, cell cycle, apoptosis, and temozolomide resistance of glioblastoma cells in vitro. Bioinformatics analyses, luciferase reporter assays, and immunoblotting showed that p53 is a target gene of miR-141-3p. A significant inverse correlation was observed between expression of miR-141-3p and p53 in glioma and normal brain tissues (R²=0.506, P<0.0001). Rescue experiments indicated that overexpression of p53 significantly reversed the alterations in proliferation, cell cycle distribution, and temozolomide resistance measured by cell apoptosis induced by miR-141-3p overexpression. In an orthotopic mouse model of human glioma, inhibition of miRNA-141-3p reduced the proliferation and growth of glioma cells in the brain and significantly prolonged the survival of glioma-bearing mice. We suggest that miR-141-3p promotes glioblastoma progression and temozolomide resistance by altering p53 expression and therefore may serve as a new diagnostic marker and therapeutic target for glioma in the future.

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.

Catalpol promotes cellular apoptosis in human HCT116 colorectal cancer cells via microRNA-200 and the downregulation of PI3K-Akt signaling pathway

Catalpol is an effective active ingredient that functions as a diuretic and laxative, and exhibits blood sugar-lowering, liver protective, anti-aging and anticancer effects. In traditional Chinese medicine, catalpol is believed to be Yin nourishing. The anticancer effect of catalpol on human HCT116 colorectal cancer cells were investigated and the mechanism of action was evaluated. Cellular viability was detected using an MTT assay. Caspase-3 and caspase-9 activity, cellular apoptosis and nucleic morphology were analyzed using caspase-3 and caspase-9 activity assay kits, flow cytometric assays and DAPI staining assay, respectively. Western blot analysis was used to measure the protein expressions of phosphatidylinositol 3-kinase (PI3K), phosphorylated-protein kinase B (p-Akt) and Akt. Expression of microRNA-200 was detected using the reverse transcription-quantitative polymerase chain reaction. HCT116 cells were incubated with PI3K inhibitors in order to analyze the effect of catalpol on cell proliferation. Catalpol was able to inhibit HCT116 cell proliferation. Furthermore, catalpol induced apoptosis in HCT116 cells, which depended on the increased activities of caspase-3 and -9. In addition, catalpol reduced the expression of PI3K, p-Akt and Akt in HCT116 cells. However, downregulation of PI3K/Akt decreased the viability of HCT116 cells following treatment with catalpol and enhanced microRNA-200 expression. Catalpol promoted cellular apoptosis in human HCT116 colorectal cancer cells through upregulation of microRNA-200 expression, which depended on a downregulation of the phosphatase and tensin homolog/PI3K-Akt signaling pathway.

Effects of Zebularine on Invasion Activity and Intracellular Expression Level of let-7b in Colorectal Cancer Cells

The effects of zebularine, a DNA methyltransferase inhibitor, on the invasion activity as well as intracellular expression level of let-7b, tumor suppressor microRNA, were examined in three human colorectal cancer (CRC) cell lines: SW480, SW620, and oxaliplatin-resistant SW620 (SW620/OxR). Zebularine suppressed the invasion activity of SW620 and SW620/OxR cells. The intracellular expression level of let-7b was up-regulated by zebularine in SW620 and SW620/OxR cells. The overexpression of let-7b by the transfection of let-7b mimic suppressed invasion activity in SW620 and SW620/OxR cells. These results suggest that zebularine may inhibit invasion activity by up-regulating the intracellular expression level of let-7b in high-invasive CRC cells.

Colorectal Cancer: From the Genetic Model to Posttranscriptional Regulation by Noncoding RNAs

Colorectal cancer is the third most common form of cancer in developed countries and, despite the improvements achieved in its treatment options, remains as one of the main causes of cancer-related death. In this review, we first focus on colorectal carcinogenesis and on the genetic and epigenetic alterations involved. In addition, noncoding RNAs have been shown to be important regulators of gene expression. We present a general overview of what is known about these molecules and their role and dysregulation in cancer, with a special focus on the biogenesis, characteristics, and function of microRNAs. These molecules are important regulators of carcinogenesis, progression, invasion, angiogenesis, and metastases in cancer, including colorectal cancer. For this reason, miRNAs can be used as potential biomarkers for diagnosis, prognosis, and efficacy of chemotherapeutic treatments, or even as therapeutic agents, or as targets by themselves. Thus, this review highlights the importance of miRNAs in the development, progression, diagnosis, and therapy of colorectal cancer and summarizes current therapeutic approaches for the treatment of colorectal cancer.

The microRNA-200 family: still much to discover

In the last decade, microRNAs (miRs or miRNAs) became of great interest in cancer research due to their multifunctional and active regulation in a variety of vital cellular processes. In this review, we discuss the miR-200 family, which is composed of five members (miR-141, miR-200a/200b/200c and miR-429). Although being among the best investigated miRNAs in the field, there are still many open issues. Here, we describe the potential role of miR-200 as prognostic and/or predictive biomarker, its influence on motility and cell migration as well as its role in epithelial to mesenchymal transition (EMT) and metastasis formation in different tumour types. Recent studies also demonstrated the influence of miR-200 on drug resistance and described a correlation between miR-200 expression levels and overall survival of patients. Despite intense research in this field, the full role of the miR-200 family in cancer progression and metastasis is not completely understood and seems to differ between different tumour types and different cellular backgrounds. To elucidate these differences further, a finer characterisation of the role of the individual miRNA-200 family members is currently under investigation.

Plasma miR-122 and miR-200 family are prognostic markers in colorectal cancer

Circulating microRNAs (miRNAs) have been proposed as minimally invasive prognostic markers for various types of cancers, including colorectal cancer (CRC), the third most diagnosed cancer worldwide. We aimed to evaluate the levels of circulating miRNAs that might serve as markers for CRC prognosis and survival. We included plasma samples of 543 CRC patients with stage I-IV disease from a population-based study carried out in Germany. After comprehensive evaluation of current literature, 95 miRNAs were selected and measured with Custom TaqMan® Array MicroRNA Cards. Plasma samples of non-metastatic and metastatic colon cancer patients, each group consisting of ten patients with 'good' and ten patients with 'bad' prognosis were screened. Identified candidate miRNAs were further validated by RT-qPCR in the whole study cohort. The association of the miRNA levels with patients' survival and the prognostic subtypes was analyzed with uni- and multivariate logistic regression and Cox proportional hazards regression models. Increased miR-122 levels were associated with a 'bad' prognostic subtype in metastatic CRC (Odds ratio: 1.563, 95% confidence interval (CI): 1.038-2.347) and a shorter relapse-free survival and overall survival for non-metastatic (Hazard ratio (HR): 1.370, 95% CI: 1.028-1.825; HR: 1.353, 95% CI: 1.002-1.828) and metastatic (HR: 1.264, 95% CI: 1.050-1.520; HR: 1.292, 95% CI: 1.078-1.548) CRC patients. Additionally, several members of the miR-200 family showed associations with patients' prognosis and correlations to clinicopathological characteristics. The here identified miRNA markers, miR-122 and the miR-200 family members, could be of use in the development of a multi-marker blood test for CRC prognosis.

Involvement of microRNA-141-3p in 5-fluorouracil and oxaliplatin chemo-resistance in esophageal cancer cells via regulation of PTEN

microRNAs (miRNAs) act as a major regulator of acquired chemo-resistance in various types of cancer therapeutics. This study investigated the contribution of miRNAs in influencing multiple drug resistance in esophageal squamous cell carcinoma (ESCC). The sensitivity of four ESCC cell lines (EC109, EC9706, TE-1 and KYSE-150) to 5-fluorouracil (5-FU) and oxaliplatin (OX) was determined by MTT assay. A 5-FU and OX-resistant subline, EC9706R, was established by continuous exposure to stepwise increasing concentration of 5-FU and OX. Microarray technology was used to compare the differential expression of miRNAs between resistant cells and parental cells. Chemo-sensitivity assay was performed to evaluate drug response in EC9706R cells transfected with miRNA mimic or inhibitor. The direct targets of miRNA were identified by employing pathway analysis and then confirmed with luciferase assay. Sixty ESCC tissue samples and their paired adjacent normal tissues were collected to validate the expression of identified miRNA. Mouse models were further utilized to investigate the function of miRNA on acquired chemo-resistance. MicroRNA panel results indicated that a total of 12 miRNAs were differentially expressed and miR-141-3p was highly over expressed in resistant cells. Inhibition of miR-141-3p reversed acquired chemo-resistance in EC9706R cells by stimulating apoptosis. The expression of miR-141-3p was significantly increased in ESCC tissue samples compared to their matched distant normal tissues. In addition, the elevated miR-141-3p expression was found to be associated with ESCC differentiation status and TNM stage. Moreover, Phosphatase and tensin homolog (PTEN) was identified as direct target of miR-141-3p. Western blot exhibited altered protein levels of PTEN, Akt, and PI3k with miR-141-3p inhibitor. An inverse correlation between PTEN expression and miR-141-3p expression was also observed in tissue samples. EC9706R xenograft mouse model became sensitized to 5-FU and OX treatment following miR-141-3p inhibitor transfection in vivo. Our study demonstrated that miR-141-3p contributed to an acquired chemo-resistance through PTEN modulation both in vitro and in vivo.

Effects of mutations in Wnt/β-catenin, hedgehog, Notch and PI3K pathways on GSK-3 activity-Diverse effects on cell growth, metabolism and cancer

Glycogen synthase kinase-3 (GSK-3) is a serine/threonine kinase that participates in an array of critical cellular processes. GSK-3 was first characterized as an enzyme that phosphorylated and inactivated glycogen synthase. However, subsequent studies have revealed that this moon-lighting protein is involved in numerous signaling pathways that regulate not only metabolism but also have roles in: apoptosis, cell cycle progression, cell renewal, differentiation, embryogenesis, migration, regulation of gene transcription, stem cell biology and survival. In this review, we will discuss the roles that GSK-3 plays in various diseases as well as how this pivotal kinase interacts with multiple signaling pathways such as: PI3K/PTEN/Akt/mTOR, Ras/Raf/MEK/ERK, Wnt/beta-catenin, hedgehog, Notch and TP53. Mutations that occur in these and other pathways can alter the effects that natural GSK-3 activity has on regulating these signaling circuits that can lead to cancer as well as other diseases. The novel roles that microRNAs play in regulation of the effects of GSK-3 will also be evaluated. Targeting GSK-3 and these other pathways may improve therapy and overcome therapeutic resistance.

Systematic review of the old and new concepts in the epithelial-mesenchymal transition of colorectal cancer

Epithelial-to-mesenchymal transition (EMT) is defined as the transformation of an epithelial cell into a spindle cell with the loss of membrane E-cadherin expression and the gain of mesenchymal markers positivity. In the field of colorectal cancer (CRC), first data about EMT was published in 1995 and more than 400 papers had been written up to March 2016. Most of them are focused on the molecular pathways and experimentally-proved chemoresistance. In the present article, an update in the field of EMT in CRC based on the review of the literature and personal experience of the authors is presented. The information about the molecular and immunohistochemical (IHC) particularities of these processes and their possible role in the prognosis of CRC were also up-dated. This article focuses on the IHC quantification of the EMT, the immunoprofile of tumor buds and on the relation between EMT, angiogenesis, and stem cells activation. The EMT-induced chemoresistance vs chemotherapy- or radiotherapy-induced EMT and cellular senescence was also synthesized for both conventional and targeted therapy. As a future perspective, the EMT-angiogenesis-stemness link could be used as a possible valuable parameter for clinical follow-up and targeted therapeutic oncologic management of patients with CRC. Association of dexamethasone and angiotensin converting enzyme inhibitors combined with conventional chemotherapies could have clinical benefits in patients with CRC. The main conclusion is that, although many studies have been published, the EMT features are still incompletely elucidated and newly discovered EMT markers provide confusing data in understanding this complicated process, which might have significant clinical impact.

Exosome-derived microRNAs contribute to prostate cancer chemoresistance

Certain microRNAs (miRNAs) play a key role in cancer cell chemoresistance. However, the pleiotropic functions of exosome-derived miRNAs on developing chemoresistance remain unknown. In the present study, we aimed to construct potential networks of miRNAs, which derived from the exosome of chemoresistant prostate cancer (PCa) cells, with their known target genes using miRNA expression profiling and bioinformatic tools. Global miRNA expression profiles were measured by microarray. Twelve miRNAs were initially selected and validated by qRT-PCR. Known targets of deregulated miRNAs were utilized using DIANA-TarBase database v6.0. The incorporation of deregulated miRNAs and target genes into KEGG pathways were utilized using DIANA-mirPath software. To construct potential miRNA regulatory networks, the overlapping parts of miRNAs and their targer genes from the selected KEGG pathway 'PCa progression (hsa05215)' were visualized by Cytoscape software. We identified 29 deregulated miRNAs, including 19 upregulated and 10 downregulated, in exosome samples derived from two kinds of paclitaxel resistance PCa cells (PC3-TXR and DU145-TXR) compared with their parental cells (PC3 and DU145). The enrichment results of deregulated miRNAs and known target genes showed that a few pathways were correlated with several critical cell signaling pathways. We found that hub hsa-miR3176, -141-3p, -5004-5p, -16-5p, -3915, -488‑3p, -23c, -3673 and -3654 were potential targets to hub gene androgen receptor (AR) and phosphatase and tensin homolog (PTEN). Hub gene T-cell factors/lymphoid enhancer-binding factors 4 (TCF4) target genes were mainly regulated by hub hsa-miR-32-5, -141-3p, -606, -381 and -429. These results may provide a linkage between PCa chemoresistance and exosome regulatory networks and thus lead us to propose that AR, PTEN and TCF4 genes may be the important genes which are regulated by exosome miRNAs in chemoresistance cancer cells.