MicroRNA Expression in KRAS- and BRAF-mutated Colorectal Cancers

An Exosomal miRNA Biomarker for the Detection of Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) remains a difficult tumor to diagnose and treat. To date, PDAC lacks routine screening with no markers available for early detection. Exosomes are 40-150 nm-sized extracellular vesicles that contain DNA, RNA, and proteins. These exosomes are released by all cell types into circulation and thus can be harvested from patient body fluids, thereby facilitating a non-invasive method for PDAC detection. A bioinformatics analysis was conducted utilizing publicly available miRNA pancreatic cancer expression and genome databases. Through this analysis, we identified 18 miRNA with strong potential for PDAC detection. From this analysis, 10 (MIR31, MIR93, MIR133A1, MIR210, MIR330, MIR339, MIR425, MIR429, MIR1208, and MIR3620) were chosen due to high copy number variation as well as their potential to differentiate patients with chronic pancreatitis, neoplasms, and PDAC. These 10 were examined for their mature miRNA expression patterns, giving rise to 18 mature miRs for further analysis. Exosomal RNA from cell culture media was analyzed via RTqPCR and seven mature miRs exhibited statistical significance (miR-31-5p, miR-31-3p, miR-210-3p, miR-339-5p, miR-425-5p, miR-425-3p, and miR-429). These identified biomarkers can potentially be used for early detection of PDAC.

Differential expression analysis of genes and long non-coding RNAs associated with KRAS mutation in colorectal cancer cells

KRAS mutation is responsible for 40–50% of colorectal cancers (CRCs). RNA-seq data and bioinformatics methods were used to analyze the transcriptional profiles of KRAS mutant (mtKRAS) in comparison with the wild-type (wtKRAS) cell lines, followed by in-silico and quantitative real-time PCR (qPCR) validations. Gene set enrichment analysis showed overrepresentation of KRAS signaling as an oncogenic signature in mtKRAS. Gene ontology and pathway analyses on 600 differentially-expressed genes (DEGs) indicated their major involvement in the cancer-associated signal transduction pathways. Significant hub genes were identified through analyzing PPI network, with the highest node degree for PTPRC. The evaluation of the interaction between co-expressed DEGs and lncRNAs revealed 12 differentially-expressed lncRNAs which potentially regulate the genes majorly enriched in Rap1 and RAS signaling pathways. The results of the qPCR showed the overexpression of PPARG and PTGS2, and downregulation of PTPRC in mtKRAS cells compared to the wtKRAS one, which confirming the outputs of RNA-seq analysis. Further, significant upregualtion of miR-23b was observed in wtKRAS cells. The comparison between the expression level of hub genes and TFs with expression data of CRC tissue samples deposited in TCGA databank confirmed them as distinct biomarkers for the discrimination of normal and tumor patient samples. Survival analysis revealed the significant prognostic value for some of the hub genes, TFs, and lncRNAs. The results of the present study can extend the vision on the molecular mechanisms involved in KRAS-driven CRC pathogenesis.

MicroRNAs Are Key Molecules Involved in the Gene Regulation Network of Colorectal Cancer

Colorectal cancer (CRC) is one of the most common types of cancer and one of the leading causes of mortality worldwide. MicroRNAs (miRNAs) play central roles in normal cell maintenance, development, and other physiological processes. Growing evidence has illustrated that dysregulated miRNAs can participate in the initiation, progression, metastasis, and therapeutic resistance that confer miRNAs to serve as clinical biomarkers and therapeutic targets for CRC. Through binding to the 3′-untranslated region (3′-UTR) of target genes, miRNAs can lead to target mRNA degradation or inhibition at a post-transcriptional level. During the last decade, studies have found numerous miRNAs and their potential targets, but the complex network of miRNA/Targets in CRC remains unclear. In this review, we sought to summarize the complicated roles of the miRNA-target regulation network (Wnt, TGF-β, PI3K-AKT, MAPK, and EMT related pathways) in CRC with up-to-date, high-quality published data. In particular, we aimed to discuss the downstream miRNAs of specific pathways. We hope these data can be a potent supplement for the canonical miRNA-target regulation network.

Emerging role of non-coding RNAs in the regulation of KRAS

The Kirsten ras oncogene KRAS is a member of the small GTPase superfamily participating in the RAS/MAPK pathway. A single amino acid substitution in KRAS gene has been shown to activate the encoded protein resulting in cell transformation. This oncogene is involved in the malignant transformation in several tissues. Notably, numerous non-coding RNAs have been found to interact with KRAS protein. Such interaction results in a wide array of human disorders, particularly cancers. Orilnc1, KIMAT1, SLCO4A1-AS1, LINC01420, KRAS1P, YWHAE, PART1, MALAT1, PCAT-1, lncRNA-NUTF2P3-001 and TP53TG1 are long non-coding RNAs (lncRNAs) whose interactions with KRAS have been verified in the context of cancer. miR-143, miR-96, miR-134 and miR-126 have also been shown to interact with KRAS in different tissues. Finally, circITGA7, circ_GLG1, circFNTA and circ-MEMO1 are examples of circular RNAs (circRNAs) that interact with KRAS. In this review, we describe the interaction between KRAS and lncRNAs, miRNAs and circRNAs, particularly in the context of cancer.

The Specific Gravity-Free Method for the Isolation of Circulating Tumor KRAS Mutant DNA and Exosome in Colorectal Cancer

Background: Circulating tumor DNA (ctDNA) and exosome have been widely researched in the field of medical technology and diagnosis platforms. The purpose of our study was to improve the capturing properties of ctDNA and exosome, which involved combining two beads using approaches that may provide a new method for cancer diagnoses. Methods: We present a dual isolation system including a polydopamine (PDA)–silica-coated alginate bead for circulating tumor DNA (ctDNA) capture and an anti-CD63 immobilized bead for exosome capture. We examined the ctDNA mutation in pre-operative plasma samples obtained from 91 colorectal cancer (CRC) patients using a droplet digital PCR (ddPCR). Results: The area under the curve (AUROC) of ctKRAS G12D mutation in the buffy coat was 0.718 (95% CI: 0.598−0.838; p = 0.001). Patients with CRC that had unmethylation of MLH1 and MSH2 showed significantly higher buffy coat ctKRAS G12D mutations, ascites ctKRAS G12D mutations, miR-31-5, and mixed scores than the patients with a methylation of MLH1 and MSH2. Conclusion: Our proposed alginate bead using the specific gravity-free method suggests that the screening of mutated ctKRAS DNA and miR-31-5 by liquid biopsy aids in identifying the patients, predicting a primary tumor, and monitoring in the early detection of a tumor.

Tumor suppressor miR-193a-3p enhances efficacy of BRAF/MEK inhibitors in BRAF-mutated colorectal cancer

Patients with BRAF‐mutated colorectal cancer (CRC) have a poor prognosis despite recent therapeutic advances such as combination therapy with BRAF, MEK, and epidermal growth factor receptor (EGFR) inhibitors. To identify microRNAs (miRNAs) that can improve the efficacy of BRAF inhibitor dabrafenib (DAB) and MEK inhibitor trametinib (TRA), we screened 240 miRNAs in BRAF‐mutated CRC cells and identified five candidate miRNAs. Overexpression of miR‐193a‐3p, one of the five screened miRNAs, in CRC cells inhibited cell proliferation by inducing apoptosis. Reverse‐phase protein array analysis revealed that proteins with altered phosphorylation induced by miR‐193a‐3p were involved in several oncogenic pathways including MAPK‐related pathways. Furthermore, overexpression of miR‐193a‐3p in BRAF‐mutated cells enhanced the efficacy of DAB and TRA through inhibiting reactivation of MAPK signaling and inducing inhibition of Mcl1. Inhibition of Mcl1 by siRNA or by Mcl1 inhibitor increased the antiproliferative effect of combination therapy with DAB, TRA, and anti‐EGFR antibody cetuximab. Collectively, our study demonstrated the possibility that miR‐193a‐3p acts as a tumor suppressor through regulating multiple proteins involved in oncogenesis and affects cellular sensitivity to MAPK‐related pathway inhibitors such as BRAF inhibitors, MEK inhibitors, and/or anti‐EGFR antibodies. Addition of miR‐193a‐3p and/or modulation of proteins involved in the miR‐193a‐3p–mediated pathway, such as Mcl1, to EGFR/BRAF/MEK inhibition may be a potential therapeutic strategy against BRAF‐mutated CRC.

Unveiling role of sphingosine-1-phosphate receptor 2 as a brake of epithelial stem cell proliferation and a tumor suppressor in colorectal cancer

Background

Sphingosine-1-phosphate receptor 2 (S1PR2) mediates pleiotropic functions encompassing cell proliferation, survival, and migration, which become collectively de-regulated in cancer. Information on whether S1PR2 participates in colorectal carcinogenesis/cancer is scanty, and we set out to fill the gap.

Methods

We screened expression changes of S1PR2 in human CRC and matched normal mucosa specimens [N = 76]. We compared CRC arising in inflammation-driven and genetically engineered models in wild-type (S1PR2^+/+) and S1PR2 deficient (S1PR2^−/−) mice. We reconstituted S1PR2 expression in RKO cells and assessed their growth in xenografts. Functionally, we mimicked the ablation of S1PR2 in normal mucosa by treating S1PR2^+/+ organoids with JTE013 and characterized intestinal epithelial stem cells isolated from S1PR2^−/−Lgr5-EGFP- mice.

Results

S1PR2 expression was lost in 33% of CRC; in 55%, it was significantly decreased, only 12% retaining expression comparable to normal mucosa. Both colitis-induced and genetic Apc^+/min mouse models of CRC showed a higher incidence in size and number of carcinomas and/or high-grade adenomas, with increased cell proliferation in S1PR2^−/− mice compared to S1PR2^+/+ controls. Loss of S1PR2 impaired mucosal regeneration, ultimately promoting the expansion of intestinal stem cells. Whereas its overexpression attenuated cell cycle progression, it reduced the phosphorylation of AKT and augmented the levels of PTEN.

Conclusions

In normal colonic crypts, S1PR2 gains expression along with intestinal epithelial cells differentiation, but not in intestinal stem cells, and contrasts intestinal tumorigenesis by promoting epithelial differentiation, preventing the expansion of stem cells and braking their malignant transformation. Targeting of S1PR2 may be of therapeutic benefit for CRC expressing high Lgr5.

Graphical Abstract. Schematic drawing of the role of S1PR2 in normal mucosa and colorectal cancer. In the normal mucosa, S1PR2 is highly expressed by differentiated cells at the upper region of both colon and intestinal crypts (S1PR2 ON), but not by the undifferentiated stem cell at the base of the crypts (S1PR2 OFF), in which acts as a negative proliferative regulator promoting epithelial differentiation. Its loss leads to the expansion of stem cells and reduced levels of PTEN and Axin-2, two negative regulators respectively of PI3K/AKT and Wnt signaling that control β-catenin signaling. The translocation of β-catenin into the nucleus promotes the transcription of target genes involved in the proliferation and malignant transformation. Thereby, S1PR2 works in the intestine as a tumor suppressor

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-020-01740-6.

Significance of miR-27a and miR-31 in early diagnosis and prognosis of colorectal cancer

Clinical significance of micro-ribonucleic acid (miR)-27a and miR-31 in the early diagnosis and prognosis of colorectal cancer were investigated. Forty patients with colorectal malignancy admitted to Xintai People's Hospital from February 2014 to April 2018 were enrolled as the observation group, of which 30 patients were diagnosed via pathological biopsy. Another 40 patients diagnosed with colorectal polyp and receiving surgical treatment were selected as the control group. The relative amount of miR-27a and miR-31 was measured. The relative expression levels of miR-27a and miR-31 in patients were analyzed. The diagnostic sensitivity, specificity and accordance rates of positive miR-27a and miR-31 expression in colorectal cancer were recorded. The correlation of the relative expression levels of miR-27a and miR-31 with the survival time of patients were analyzed. In the observation group, the relative expression levels of miR-27a and miR-31 in patients with lymph node metastasis and distant metastasis were higher than those in patients without lymph node metastasis and distant metastasis (P<0.05). Histological type of patients with non-mucinous carcinoma had increased relative expression levels of miR-27a and miR-31 in comparison with those with mucinous carcinoma (P<0.05). In terms of Duke's grade, the relative expression levels of miR-27a and miR-31 in patients with grade C and D were higher than those in patients with grade A and B (P<0.05). The diagnostic sensitivity, specificity and accordance rate of positive miR-27a expression were lower than those of positive miR-31 expression. The relative expression levels of miR-27a and miR-31 were positively correlated with the survival time of patients (P<0.05). The expression levels of miR-27a and miR-31 are related to distant metastasis and tumor grade of patients with colorectal cancer, and positively associated with the survival time of patients, having high diagnostic value.

Emerging microRNA biomarkers for colorectal cancer diagnosis and prognosis

MicroRNAs (miRNAs) are one abundant class of small, endogenous non-coding RNAs, which regulate various biological processes by inhibiting expression of target genes. miRNAs have important functional roles in carcinogenesis and development of colorectal cancer (CRC), and emerging evidence has indicated the feasibility of miRNAs as robust cancer biomarkers. This review summarizes the progress in miRNA-related research, including study of its oncogene or tumour-suppressor roles and the advantages of miRNA biomarkers for CRC diagnosis, treatment and recurrence prediction. Along with analytical technique improvements in miRNA research, use of the emerging extracellular miRNAs is feasible for CRC diagnosis and prognosis.

MiR-769 Inhibits Colorectal Cancer Cell Proliferation and Invasion by Targeting HEY1

BACKGROUND MicroRNAs (miRNAs) have been widely recognized as essential regulators in human cancers, including colorectal cancer (CRC). Whether miR-769 is implicated in CRC progression remains elusive. The present study aimed to determine the function of miR-769 in CRC. MATERIAL AND METHODS MiR-769 expression in CRC tissues and adjacent normal tissues were measured by quantitative real-time polymerase chain reaction (qRT-PCR) and in situ hybridization. Kaplan-Meier curve analysis was utilized to determine the association between miR-769 expression and prognosis in CRC patients. The effects of miR-769 overexpression on CRC cell proliferation, cell cycle and invasion were analyzed using Cell Counting Kit-8 (CCK8), fluorescence activated cell sorting (FACS), and Transwell assays. Western blot was utilized to assess the effect of miR-769 on HEY1 expression. RESULTS MiR-769 expression was decreased in CRC tissues. MiR-769 level was negatively correlated with the prognosis of CRC patients. Additionally, miR-769 overexpression remarkably inhibited cell proliferation, arrested CRC cells in G0 stage, and reduced cellular invasion. As to the mechanism, HEY1 was a direct target of miR-769; HEY1 level was inversely correlated with that of miR-769 in CRC tissues. Finally, overexpression of HEY1 reversed the effects of miR-769 on cell proliferation and invasion in CRC. CONCLUSIONS Our findings demonstrated that miR-769 suppressed the proliferation and invasion of CRC cells through targeting HEY1, which implied that miR-769 might be a novel therapeutic target for CRC treatment.

A comprehensive look at the role of hyperlipidemia in promoting colorectal cancer liver metastasis

Colorectal cancer (CRC) is one of the most malignant cancers, and it tends to migrate to the liver and has a high mortality rate. Several mechanisms behind the metastasis of CRC have been identified, including hyperlipidemia. For example, hyperlipidemia can lead to enhanced stemness and neutrophil infiltration, which increases CRC metastasis. There are three primary aspects to the relationship between hyperlipidemia and CRC metastasis: hyperlipidemia (1) promotes the initial metastatic properties of CRC, (2) stimulates CRC cells to leave the vasculature, and (3) facilitates the development of CRC metastasis. In this study, we provide a comprehensive overview of the role that hyperlipidemia played in CRC metastasis to help reduce the mortality associated with CRC metastasis from the standpoint of metabolic. We also review cancer metastasis.