microRNA-26a and -584 inhibit the colorectal cancer progression through inhibition of the binding of hnRNP A1-CDK6 mRNA

Readers of RNA Modification in Cancer and Their Anticancer Inhibitors

Cancer treatment has always been a challenge for humanity. The inadequacies of current technologies underscore the limitations of our efforts against this disease. Nevertheless, the advent of targeted therapy has introduced a promising avenue, furnishing us with more efficacious tools. Consequently, researchers have turned their attention toward epigenetics, offering a novel perspective in this realm. The investigation of epigenetics has brought RNA readers to the forefront, as they play pivotal roles in recognizing and regulating RNA functions. Recently, the development of inhibitors targeting these RNA readers has emerged as a focal point in research and holds promise for further strides in targeted therapy. In this review, we comprehensively summarize various types of inhibitors targeting RNA readers, including non-coding RNA (ncRNA) inhibitors, small-molecule inhibitors, and other potential inhibitors. We systematically elucidate their mechanisms in suppressing cancer progression by inhibiting readers, aiming to present inhibitors of readers at the current stage and provide more insights into the development of anticancer drugs.

Molecular detection of exosomal miRNAs of blood serum for prognosis of colorectal cancer

Colorectal cancer (CRC) is the third most common cancer affecting people. The discovery of new, non-invasive, specific, and sensitive molecular biomarkers for CRC may assist in the diagnosis and support therapeutic decision making. Exosomal miRNAs have been demonstrated in carcinogenesis and CRC development, which makes these miRNAs strong biomarkers for CRC. Deep sequencing allows a robust high-throughput informatics investigation of the types and abundance of exosomal miRNAs. Thus, exosomal miRNAs can be efficiently examined as diagnostic biomarkers for disease screening. In the present study, a number of 660 mature miRNAs were detected in patients diagnosed with CRC at different stages. Of which, 29 miRNAs were differentially expressed in CRC patients compared with healthy controls. Twenty-nine miRNAs with high abundance levels were further selected for subsequent analysis. These miRNAs were either highly up-regulated (e.g., let-7a-5p, let-7c-5p, let-7f-5p, let-7d-3p, miR-423-5p, miR-3184-5p, and miR-584) or down-regulated (e.g., miR-30a-5p, miR-99-5p, miR-150-5p, miR-26-5p and miR-204-5p). These miRNAs influence critical genes in CRC, leading to either tumor growth or suppression. Most of the reported diagnostic exosomal miRNAs were shown to be circulating in blood serum. The latter is a novel miRNA that was found in exosomal profile of blood serum. Some of the predicted target genes of highly expressed miRNAs participate in several cancer pathways, including CRC pathway. These target genes include tumor suppressor genes, oncogenes and DNA repair genes. Main focus was given to multiple critical signaling cross-talking pathways including transforming growth factor β (TGFβ) signaling pathways that are directly linked to CRC. In conclusion, we recommend further analysis in order to experimentally confirm exact relationships between selected differentially expressed miRNAs and their predicted target genes and downstream functional consequences.

miR-584-5p Inhibits Osteosarcoma Progression by Targeting Connective Tissue Growth Factor

Background: miR-584-5p is a critical regulator in the progression of multiple cancers. However, its specific role and downstream targets in osteosarcoma are unclear. This research investigated the roles and underlying mechanisms of miR-769-5p and the Hippo pathway in osteosarcoma cells. Materials and Methods: RT-qPCR, CCK-8 and EdU and colony formation, wound-healing and transwell chamber, flow cytometry, and Western blot assay detected the expression of miR-584-5p and CTGF, cell proliferation, migration, invasion apoptosis and protein expression. Result: Their study illuminated that miR-584-5p overexpression repressed osteosarcoma cell migration/invasion and proliferation and facilitated apoptosis. Mechanistically, miR-584-5p targets negatively regulated connective tissue growth factor (CTGF). miR-584-5p inhibited osteosarcoma cell metastasis by regulating CTGF. In addition, miR-584-5p inactivated the Hippo pathway through CTGF in osteosarcoma. Conclusion: miR-584-5p inhibits osteosarcoma cell proliferation, migration, and invasion and promotes apoptosis by targeting CTGF, indicating that miR-584-5p acts as a promising diagnostic and predictive biomarker for osteosarcoma.

Decaying kidney function during cirrhosis correlates with remodeling of distal colon aldosterone target gene expression

Liver cirrhosis is associated to circulatory abnormalities leading to hypovolemia and stimulation of the renin-angiotensin-aldosterone system (RAAS). Advanced stages of the disease cause renal failure, impairing K+ and Na+ homeostasis. It has been proposed that the distal colon undergoes functional remodeling during renal failure, in particular by aldosterone-driven increased K+ excretion. In this study, we compared the transcriptional response of aldosterone target genes in the rat distal colon under two models of increased circulating aldosterone (one with concomitant RAAS activation) and in a model of secondary hyperaldosteronism induced by cirrhosis. The expression of a subset of these genes was also tested in distal colon biopsies from control subjects or patients with cirrhosis with varying levels of disease progression and treated or not with mineralocorticoid receptor inhibitor spironolactone. We examined known aldosterone-regulated transcripts involved in corticosteroid signaling and transepithelial ion transport. In addition, we included aldosterone-regulated genes related to cell proliferation. Our comparison revealed multiple aldosterone target genes upregulated in the rat distal colon during decompensated cirrhosis. Epithelial Na+ channel β and γ subunit expression correlated positively with plasma aldosterone concentration and negatively with glomerular filtration rate. Patients with cirrhosis showed increased expression of 11-β-hydroxysteroid-dehydrogenase 2 (11βHSD2), which was reverted by spironolactone treatment, suggesting a sensitization of the distal colon to aldosterone action. In summary, our data show that decaying kidney function during cirrhosis progression toward a decompensated state with hypovolemia correlates with remodeling of distal colon ion transporter expression, supporting a role for aldosterone in the process.NEW & NOTEWORTHY Liver cirrhosis progression significantly alters ion transporter subunit expression in the rat distal colon, a change that correlated well with declining kidney function and the severity of the disease. Our data suggest that the steroid hormone aldosterone participates in this homeostatic response to maintain electrolyte balance.

Heterogeneous nuclear ribonucleoprotein A/B: an emerging group of cancer biomarkers and therapeutic targets

Heterogeneous nuclear ribonucleoprotein A/B (hnRNPA/B) is one of the core members of the RNA binding protein (RBP) hnRNPs family, including four main subtypes, A0, A1, A2/B1 and A3, which share the similar structure and functions. With the advance in understanding the molecular biology of hnRNPA/B, it has been gradually revealed that hnRNPA/B plays a critical role in almost the entire steps of RNA life cycle and its aberrant expression and mutation have important effects on the occurrence and progression of various cancers. This review focuses on the clinical significance of hnRNPA/B in various cancers and systematically summarizes its biological function and molecular mechanisms.

HNRNPA2B1 as a trigger of RNA switch modulates the miRNA-mediated regulation of CDK6

The functional inactivation of tumor suppressor microRNA (miRNA) is closely related to the tumorigenesis of cancer. There are instances where the miRNA and the corresponding target both exist in a cell, but the target gene silencing do not occur as expected. Herein, we found that both miR-506 and its target CDK6 are highly co-expressed in lung cancer cells. Sequence analyses suggested that a miR-506 binding site (1648–1654) and a cis-element (1785–1795) for binding by heterogeneous nuclear ribonucleoprotein A2/B1 (HNRNPA2B1) are evolutionarily conserved and forms a stem structure in the 3′ untranslated region (3′UTR) of CDK6. Furthermore, HNRNPA2B1 can bind to the stem structure to denature it and recruit the RNA helicase DExH-box helicase 9 (DHX9) to the 3′UTR, which ultimately facilitates miRNAs-mediated CDK6 silencing. These results indicate that the cis-element of the 3′UTR of CDK6, where HNRNPA2B1 binds, serves as an RNA switch to regulate miRNAs’ function in cancer cells.

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Both miR-506 and its target CDK6 are highly co-expressed in lung cancer

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HNRNPA2B1 facilitates miR-506-mediated CDK6 silence by switching structure in 3′UTR

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HNRNPA2B1 also recruits the DHX9 to the 3′UTR of its targets

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HNRNPA2B1 extensively regulates miRNAs-mediated gene silencing through binding to 3′UTR

Tumor-Progressive Mechanisms Mediating miRNA-Protein Interaction

MicroRNAs (miRNAs) are single-stranded short-chain RNAs that are endogenously expressed in vertebrates; they are considered the fine-tuners of cellular protein expression that act by modifying mRNA translation. miRNAs control tissue development and differentiation, cell growth, and apoptosis in cancer and non-cancer cells. Aberrant regulation of miRNAs is involved in the pathogenesis of various diseases including cancer. Numerous investigations have shown that the changes in cellular miRNA expression in cancerous tissues and extracellular miRNAs enclosed in exosomes are correlated with cancer prognosis. Therefore, miRNAs can be used as cancer biomarkers and therapeutic targets for cancer in clinical applications. In the previous decade, miRNAs have been shown to regulate cellular functions by directly binding to proteins and mRNAs, thereby controlling cancer progression. This regulatory system implies that cancer-associated miRNAs can be applied as molecular-targeted therapy. This review discusses the roles of miRNA-protein systems in cancer progression and its future applications in cancer treatment.

The Identification of RNA-Binding Proteins Functionally Associated with Tumor Progression in Gastrointestinal Cancer

Simple Summary

Previous investigations described bioinformatic analyses based on the mRNA expression and somatic mutation as useful strategies for identifying cancer-associated molecules that were potential candidates of therapeutic targets. However, these data included secondary changes and non-functional alterations that do not influence tumor progression. Investigations, including our own studies, have shown that some RBPs shuttle cytoplasm and nuclei, and their affinity to RNAs is regulated by posttranslational modifications, such as phosphorylation. Therefore, the functional assessment of individual molecules is the most suitable strategy for identifying cancer-associated genes with or without expressional changes and mutations. This report showed for the first time that a functional assessment using an siRNA library was useful for identifying therapeutic targets from molecular groups, including RBPs, that had not been identified by expressional and mutational analyses.

Abstract

Previous investigations have indicated that RNA-binding proteins (RBPs) are key molecules for the development of organs, differentiation, cell growth and apoptosis in cancer cells as well as normal cells. A bioinformatics analysis based on the mRNA expression and a somatic mutational database revealed the association between aberrant expression/mutations of RBPs and cancer progression. However, this method failed to detect functional alterations in RBPs without changes in the expression, thus leading to false negatives. To identify major tumor-associated RBPs, we constructed an siRNA library based on the database of RBPs and assessed the influence on the growth of colorectal, pancreatic and esophageal cancer cells. A comprehensive analysis of siRNA functional screening findings using 1198 siRNAs targeting 416 RBPs identified 41 RBPs in which 50% inhibition of cell growth was observed in cancer cells. Among these RBPs, 12 showed no change in the mRNA expression and no growth suppression in non-cancerous cells when downregulated by specific siRNAs. We herein report for the first time cancer-promotive RBPs identified by a novel functional assessment using an siRNA library of RBPs combined with expressional and mutational analyses.

The bioactivity of colostrum and milk exosomes of high, average, and low immune responder cows on human intestinal epithelial cells

Bovine milk contains bioactive components that are nutritionally and immunologically important to calves and humans. Dairy cows classified as high (H) immune responders using the patented high immune response technology have higher concentrations of immunoglobulin and specific antibodies in sera and milk compared with average (A) and low (L) responders. MicroRNA post-transcriptionally regulate expression of milk bioactive components and are enriched in extracellular vesicles known as exosomes, which protect them from degradation. The bioactivity of colostrum and milk exosomes at the human intestinal epithelial barrier remains to be explored, particularly in the context of the high immune response technology. Therefore, the purpose of this study was to evaluate the functional role of bovine milk exosomes compared with colostrum exosomes from H, A, and L responders at the intestinal interface using human colorectal adenocarcinoma epithelial (Caco-2) cells. Exosomes were isolated by successive ultracentrifugation and confirmed by western blot analysis for the presence of common exosomal proteins (CD9, CD63, and heat shock protein 70). Fluorescent labeling of exosomes using PKH67 dye confirmed their uptake by Caco-2 cells, demonstrating their potential bioavailability. The MTT assays showed that colostrum and milk exosomes maintain Caco-2 metabolic activity and are not cytotoxic to these cells. Specifically, metabolic activity after co-incubation with colostrum and milk exosomes from H responder cows was significantly greater than after co-incubation with exosomes from L responders. Caspase 3 activity, an indicator of apoptosis, was significantly lower after co-incubation of Caco-2 cells with milk exosomes compared with colostrum exosomes, suggesting that unlike colostrum exosomes, particularly those from L responders, milk exosomes do not activate the caspase 3 pathway in Caco-2 cells. This study helps us better understand the functional importance of colostrum and milk exosomes from dairy cows and emphasizes differences in functionality among exosomes from H, A, and L immune responders.

A tumor-specific modulation of heterogeneous ribonucleoprotein A0 promotes excessive mitosis and growth in colorectal cancer cells

RNA regulation mediating RNA-binding proteins (RBPs) have been shown to be related to the maintenance of homeostasis as well as cancer progression. However, the tumor-associated functions as well as the detailed mechanisms underlying the anti-tumor effects of most RBPs have yet to be explored. We herein report that the phosphorylated heterogeneous ribonucleoprotein (hnRNP) A0 promotes mitosis through the RAS-associated protein 3 GTPase-activating protein catalytic subunit 1 (RAB3GAP1)-Zeste white 10 interactor (ZWINT1) cascade. The downregulation assay of 20 representative hnRNPs, a major family of RNA-binding proteins, in colorectal cancer cells revealed that hnRNPA0 is a strong regulator of cancer cell growth. The tumor promotive function of hnRNPA0 was confirmed in gastrointestinal cancer cells, including pancreatic, esophageal, and gastric cancer cells, but not in non-cancerous cells. Flow cytometry and Western blotting analyses revealed that hnRNPA0 inhibited the apoptosis through the maintenance of G2/M phase promotion in colorectal cancer cells. A comprehensive analysis of mRNAs regulated by hnRNP A0 and immunostaining revealed that mitotic events were regulated by the hnRNPA0-RAB3GAP1 mRNA-mediated ZWINT-1 stabilization in colorectal cancer cells, but not in non-tumorous cells. The interaction of hnRNP A0 with mRNAs was dramatically changed by the deactivation of its phosphorylation site in cancer cells, but not in non-tumorous cells. Therefore, the tumor-specific biological functions characterized by the abnormal phosphorylation of RBPs are considered to be an attractive target for tumor treatment.

Persistence of Drug-Resistant Leukemic Stem Cells and Impaired NK Cell Immunity in CML Patients Depend on MIR300 Antiproliferative and PP2A-Activating Functions

Persistence of drug-resistant quiescent leukemic stem cells (LSC) and impaired natural killer (NK) cell immune response account for relapse of chronic myelogenous leukemia (CML). Inactivation of protein phosphatase 2A (PP2A) is essential for CML-quiescent LSC survival and NK cell antitumor activity. Here we show that MIR300 has antiproliferative and PP2A-activating functions that are dose dependently differentially induced by CCND2/CDK6 and SET inhibition, respectively. MIR300 is upregulated in CML LSCs and NK cells by bone marrow microenvironment (BMM) signals to induce quiescence and impair immune response, respectively. Conversely, BCR-ABL1 downregulates MIR300 in CML progenitors to prevent growth arrest and PP2A-mediated apoptosis. Quiescent LSCs escape apoptosis by upregulating TUG1 long noncoding RNA that uncouples and limits MIR300 function to cytostasis. Genetic and pharmacologic MIR300 modulation and/or PP2A-activating drug treatment restore NK cell activity, inhibit BMM-induced growth arrest, and selectively trigger LSC apoptosis in vitro and in patient-derived xenografts; hence, the importance of MIR300 and PP2A activity for CML development and therapy.

miR- 26a Sensitizes Melanoma Cells To Dabrafenib Via Targeting HMGB1-Dependent Autophagy Pathways

Background

Melanoma is known as the most aggressive and lethal type of cutaneous cancer due to its rapid development of drug resistance to chemotherapy drugs.

Methods

In our study, we conducted a variety of studies, including quantitative PCR, Western blot, and autophagy and apoptosis assays to investigate the involvement of miR-26a and HMGB1 in modulation of dabrafenib sensitivity in human melanoma cell lines.

Results

Our studies revealed that the expressions of miR-26a and HMGB1 were altered in two melanoma cell lines after dabrafenib treatment. Additionally, dabrafenib caused autophagy in melanoma and this autophagic process was regulated by miR-26a via modifying HMGB1 expression. Furthermore, silencing HMGB1-inhibited autophagy induced by dabrafenib in melanoma cells. Last, we verified that treatment with a miR-26a mimic and HMGB1 shRNA could increase the efficacy of dabrafenib in melanoma cells.

Conclusion

Taken together, we showed that miR-26a is involved in the regulation of dabrafenib efficacy via a HMGB1-dependent autophagy pathway in melanoma cells. These results shed light on a novel treatment for conventional dabrafenib-based chemotherapy for melanoma.

MicroRNA-9 exerts antitumor effects on hepatocellular carcinoma progression by targeting HMGA2

Accumulating evidence has demonstrated that the aberrant expression of microRNAs (miRs or miRNAs) may contribute to the initiation and progression of various types of human cancer and may also constitute biomarkers for cancer diagnosis and therapy. However, the specific function of miR‐9 in hepatocellular carcinoma (HCC) remains unclear, and the mechanisms that underlie HCC are incompletely understood. Here, we report that miR‐9 expression was significantly decreased in clinical tumor tissue samples, as well as in a cohort of HCC cell lines. In addition, it was demonstrated that overexpression of miR‐9 suppressed the proliferative and migratory capacity of HCC cells and impaired cell cycle progression. Furthermore, high mobility group AT‐hook 2 (HMGA2) was verified as a downstream target gene of miR‐9 using a luciferase reporter assay. Quantitative RT‐PCR and western blotting implicated HMGA2 in the miR‐9‐mediated reduction of HCC cell growth. In vivo, transfection with miR‐9 mimics down‐regulated the expression of HMGA2, thus leading to a dramatic reduction in tumor growth in a mouse xenograft model. These results suggest that miR‐9 may exert critical antitumor effects on HCC by directly targeting HMGA2, and the miR9/HMGA2 signaling pathway may be of use for the diagnosis and prognosis of patients with HCC.

LncRNA SNHG6 promotes the migration, invasion, and epithelial-mesenchymal transition of colorectal cancer cells by miR-26a/EZH2 axis

Objective: Colorectal cancer (CRC) is a leading cause of cancer-related deaths worldwide. Small nucleolar RNA host gene 6 (SNHG6) was reported to function as an oncogene in a number of cancers. Here, we aimed to further explore the roles and molecular mechanism of SNHG6 in CRC metastasis.

Methods: The expression levels of SNHG6, miR-26a, and enhancer of zeste homolog 2 (EZH2) mRNA were assessed by quantification real-time PCR in CRC tissues and cell lines. Western blot analysis was performed to determine the levels of E-cadherin, Snail, Vimentin, N-cadherin, and EZH2. Cell migration and invasion capacities were detected by transwell assay. Dual-luciferase reporter assay or RNA Immunoprecipitation assay was employed to verify the interaction between SNHG6 and miR-26a, or EZH2 and miR-26a.

Results: Our data indicated that SNHG6 and EZH2 mRNA were upregulated, and miR-26a was downregulated in CRC tissues and cell lines. SNHG6 knockdown suppressed the migration, invasion, and epithelial-mesenchymal transition (EMT) of CRC cells. Moreover, SNHG6 binded to miR-26a and repressed miR-26a expression. EZH2 was a direct target of miR-26a, and it was regulated by SNHG6/miR-26a. MiR-26a inhibitor undermined the effect of SNHG6 knockdown on cell migration, invasion, and EMT. Additionally, EZH2 antagonized the effect of miR-26a on cell migration, invasion, and EMT in CRC cells.

Conclusion: SNHG6 knockdown suppressed cell migration, invasion, and EMT at least partly by sponging miR-26a and regulating EZH2 expression in CRC cells, providing a strategy for blocking CRC metastasis.

MicroRNA-26a inhibits multiple myeloma cell growth by suppressing cyclin-dependent kinase 6 expression

MicroRNA-26a (miR-26a) has been reported to be involved in the tumorigenesis of several tumors, but its biological function and molecular mechanism in multiple myeloma (MM) are still unknown. In this study, we found that overexpression of miR-26a obviously inhibited MM cell growth, and delayed tumor growth in xenografts. Further studies showed that overexpression of miR-26a induced cell cycle arrest at G0/G1 phase in MM cells. MiR-26a mimic down-regulated the expression levels of CDK6 and E2F1, but up-regulated p53 and p21 expression. In contrast, overexpression of CDK6 decreased the effect of miR-26a mimic on MM cell survival. Moreover, miR-26a targeted CDK6 mRNA and thus suppressed CDK6 protein expression. Overexpression of miR-26a also enhanced the cytotoxic action of doxorubicin against MM. These results demonstrated that miR-26a was involved in the development of MM through regulating CDK6 signaling pathway, and indicated that miR-26a could be as a novel target for anti-tumor therapy in clinic as a single strategy or in combination with other anti-tumor drugs in MM.

Overexpression of microRNA‑101 causes anti‑tumor effects by targeting CREB1 in colon cancer

Accumulating evidence has demonstrated that aberrantly expressed microRNAs (miRNAs) are involved in the initiation and progression of numerous types of human cancer. Although a number of miRNAs have been demonstrated to be associated with the diagnosis, progression and prognosis of colon cancer, the function of miRNA‑101 (miR‑101) in colon cancer remains unclear, and the molecular mechanisms underlying the effects of miR‑101 in colon cancer require further investigation. The present study investigated the role of miR‑101 in colon cancer, and the results suggested that miR‑101 expression levels were significantly decreased in colorectal carcinoma tissues and in three types of colorectal cancer cell lines. Furthermore, overexpression of miR‑101 inhibited cell proliferation and migration in HT29 cells. The transcription factor cAMP responsive element binding protein 1 (CREB1) was identified to be a direct target of miR‑101 using a luciferase reporter assay, reverse transcription‑quantitative polymerase chain reaction analysis and western blot assay. miR‑101 overexpression in tumor xenografts in vivo decreased the expression levels of proliferating cell nuclear antigen and CREB1, and suppressed tumor growth. The present results suggested that miR‑101 may serve a role in colon cancer by directly targeting CREB1. Collectively, the present study may contribute to the development of improved diagnosis and prognostics for colon cancer.

lncRNA SNHG6 regulates EZH2 expression by sponging miR-26a/b and miR-214 in colorectal cancer

BACKGROUND

Abnormal expression of long non-coding RNAs (lncRNAs) has been found in almost all human tumors, providing numerous potential diagnostic biomarkers, prognostic biomarkers, and therapeutic targets.

METHODS

We analyzed RNA sequencing data to explore abnormally expressed lncRNAs in colorectal cancer (CRC). The functions of small nucleolar RNA host gene 6 (SNHG6) were investigated through in vitro and in vivo assays (CCK-8 assay, colony formation assay, flow cytometry assay, EdU assay, wound healing assay, transwell assay, and xenograft model). The mechanism of action of SNHG6 was explored through bioinformatics, RNA fluorescence in situ hybridization, luciferase reporter assay, RNA pull-down assay, chromatin immunoprecipitation assay, and RNA immunoprecipitation assay.

RESULTS

We identified aberrantly expressed lncRNAs in CRC. We found that elevated SNHG6 expression was associated with poor prognosis and CRC progression. We also demonstrated that the high SNHG6 expression was partly due to DNA copy number gains and SP1 induction. Functional studies showed that SNHG6 promoted CRC cell growth, migration, and invasion both in vitro and in vivo. Mechanistically, we found that SNHG6 expressed predominantly in the cytoplasm. SNHG6 could interact with miR-26a, miR-26b, and miR-214 and regulate their common target EZH2.

CONCLUSIONS

Our study elucidated that SNHG6 acted as an oncogene in CRC, which might serve as a novel target for CRC diagnosis and therapy.

Epigenetic Regulation by lncRNAs: An Overview Focused on UCA1 in Colorectal Cancer

Colorectal cancers have become the second leading cause of cancer-related deaths. In particular, acquired chemoresistance and metastatic lesions occurring in colorectal cancer are a major challenge for chemotherapy treatment. Accumulating evidence shows that long non-coding (lncRNAs) are involved in the initiation, progression, and metastasis of cancer. We here discuss the epigenetic mechanisms through which lncRNAs regulate gene expression in cancer cells. In the second part of this review, we focus on the role of lncRNA Urothelial Cancer Associated 1 (UCA1) to integrate research in different types of cancer in order to decipher its putative function and mechanism of regulation in colorectal cancer cells. UCA1 is highly expressed in cancer cells and mediates transcriptional regulation on an epigenetic level through the interaction with chromatin modifiers, by direct regulation via chromatin looping and/or by sponging the action of a diversity of miRNAs. Furthermore, we discuss the role of UCA1 in the regulation of cell cycle progression and its relation to chemoresistance in colorectal cancer cells.

Suppressive effect of an analog of the antimicrobial peptide of LL‑37 on colon cancer cells via exosome‑encapsulated miRNAs

Antimicrobial peptides (AMPs) are multifunctional factors with an important role in the innate immune system. Our previous studies revealed that the human cathelicidin LL-37 and its analog, FF/CAP18, limit the proliferation of colon cancer cell lines. In the present study, the exosomes released by HCT116 cells treated with FF/CAP18 were analyzed. After the treatment, exosomes were isolated from the culture supernatant by ultrafiltration and using the miRCURY™ Exosome Isolation Kit. Membrane vesicles 40-100-nm expressing CD63 and CD81 were identified before and after FF/CAP18 treatment. Exosome concentration in the culture supernatant was increased after treatment with FF/CAP18. Exosomes formed in HCT116 cells treated with FF/CAP18 induced growth suppression of the cells in a dose-dependent manner. By contrast, the exosomes formed in non-treated HCT116 cells did not affect cell viability. Microarray analysis of miRNA expression indicated that FF/CAP18 treatment induced increases in the expression of three miRNAs (miR-584-5p, miR-1202 and miR-3162-5p) in both HCT116 cells and exosomes. These results suggest that FF/CAP18 treatment increases exosome formation, and that exosome-encapsulated miRNAs suppress HCT116 cell proliferation. Exosomal miRNAs are considered to be involved in the dissemination of cell signals to control local cellular microenvironments. The present findings suggest that FF/CAP18 regulates cancer growth by modulating cell-to-cell communication. AMPs localize in the cytoplasm of cancer cells and enhance the expression of growth-suppressing miRNAs. These miRNAs are also transported to other cancer cells via exosomes. Therefore, transportation of these miRNAs has the potential to suppress cancer growth. AMPs exert their effects directly by targeting cancer cells and indirectly via exosomes.

microRNA-451-modulated hnRNP A1 takes a part in granulocytic differentiation regulation and acute myeloid leukemia

Myelopoiesis is under the control of a complex network containing various regulation factors. Deregulation of any important regulation factors may result in serious consequences including acute myeloid leukemia (AML). In order to find out the genes that may take a part in AML development, we analyzed data from AML cDNA microarray (GSE2191) in the NCBI data pool and noticed that heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) is abnormally over-expressed in AML patients. Then we investigated the function and mechanisms of hnRNP A1 in myeloid development. A gradually decreased hnRNP A1 expression was detected during granulocytic differentiation in ATRA-induced-NB4 and HL-60 cells and cytokines-induced hematopoietic stem and progenitor cells. By function-loss and winning experiments we demonstrated hnRNP A1's inhibition role via inhibiting expression of C/EBPα, a key regulator of granulocytic differentiation, in the granulocytic differentiation. During granulocytic differentiation the decrease of hnRNP A1 reduces inhibition on C/EBPα expression, and the increased C/EBPα promotes the differentiation. We also demonstrated that miR-451 promotes granulocytic differentiation via targeting to and down-regulating hnRNP A1, and hnRNP A1 positively regulates c-Myc expression. Summarily, our results revealed new function and mechanisms of hnRNP A1 in normal granulocytiesis and the involvement of a feed-back loop comprising c-Myc, miR-451 and hnRNP A1 in AML development.

Tumor-suppressive miR-26a and miR-26b inhibit cell aggressiveness by regulating FUT4 in colorectal cancer

Metastasis is a multistep molecular network process, which is the major cause of death in patients with colorectal cancer (CRC). MicroRNAs (miRNAs) play pivotal roles in tumorigenesis as either tumor suppressors or oncogenes. Increased expression of fucosyltransferase4 (FUT4) has been reported to be associated with the invasive and metastatic properties of CRC. Here to identify potential key miRNAs and their target genes for colorectal cancer (CRC), we compared miRNA expression profiles between metastatic CRC cell SW620 and primary CRC cell SW480. Microarray analysis revealed that there were 85 differentially expressed miRNAs in SW620 cells with highly metastatic potential compared to SW480 cells with lowly metastatic potential. The expression of miR-26a and miR-26b were lower in SW620 cells than in SW480 cells, as well as downregulated in tumor tissues than in adjacent normal tissues of CRC patients. By applying bioinformatic approaches for the prediction of miRNA targeting 3'-UTR of FUT4, we identified FUT4 as one of the miR-26a/26b-targeted genes, while the expression of the target gene exhibited patterns opposite to that of miR-26a/26b in CRC cell lines, tumor tissues and corresponding adjacent tissues. Forced miR-26a/26b expression affected migratory behavior of CRC cells and FUT4 expression, while altered expression of FUT4 in CRC cell lines modulated progression upon transfection with miR-26a/26b mimic or inhibiter. FUT4 also regulated directly aggressiveness of SW620 and SW480 cells. Moreover, statistical analyses revealed that low miR-26a/26b levels and high expression of FUT4 were positively correlated with poor overall survival. The identified CRC-restricted miR-26a and miR-26b might be implicated in cancer progression via their target gene FUT4, suggesting their potential usage in CRC treatment.

Upregulation of miR-101 enhances the cytotoxic effect of anticancer drugs through inhibition of colon cancer cell proliferation

This study investigated the effect of miR-101 on proliferation, migration, invasion, and chemotherapy sensitivity in colon cancer cell lines HT-29 and RKO. MicroRNAs are a class of small noncoding RNA molecules, which play important roles in diverse biological processes of human cancers, such as carcinogenesis, development, differentiation, and apoptosis. The expression of miR-101 in colon cancer and adjacent non-tumor tissues were examined by quantitative real-time polymerase chain reaction. The expression of miR-101 was upregulated by recombinant adenovirus Ad-miR-101. Cell proliferation was detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and cloning methods. Cell migration and invasion potential were examined using Transwell migration and Matrigel invasion chamber assays. Drug sensitivity to 5-fluorouracil (5-FU) and cisplatin (DDP) was explored using MTT assays and l acridine orange/ethidium bromide double staining. The expression of miR-101 decreased in colon cancer tissues compared with adjacent non-tumor tissues. The upregulated expression of miR-101 suppressed cell proliferation and inhibited cell migration and invasion in HT-29 and RKO colon cancer cell lines. The overexpression of miR-101 promoted the inhibitory effect of 5-FU and DDP on HT-29 cells. The expression of miR-101 was downregulated in colon cancer. The upregulated expression of miR-101 inhibited proliferation and migration, and increased the sensitivity of colon cancer cells to chemotherapy.

MicroRNAs: Potential candidates for diagnosis and treatment of colorectal cancer

Colorectal cancer (CRC) is known as the third common cancer worldwide and an important public health problem in different populations. Several genetics and environmental risk factors are involved in the development and progression of CRC including chromosomal abnormalities, epigenetic alterations, and unhealthy lifestyle. Identification of risk factors and biomarkers could lead to a better understanding of molecular pathways involved in CRC pathogenesis. MicroRNAs (miRNAs) are important regulatory molecules which could affect a variety of cellular and molecular targets in CRC. A large number of studies have indicated deregulations of some known tissue-specific miRNAs, for example, miR-21, miR-9, miR-155, miR-17, miR-19, let-7, and miR-24 as well as circulating miRNAs, for example, miR-181b, miR-21, miR-183, let-7g, miR-17, and miR-126, in patients with CRC. In the current review, we focus on the findings of preclinical and clinical studies performed on tissue-specific and circulating miRNAs as diagnostic biomarkers and therapeutic targets for the detection of patients at various stages of CRC.

microRNA-495 promotes bladder cancer cell growth and invasion by targeting phosphatase and tensin homolog

Accumulating evidence has linked deregulation of microRNA-495 (miR-495) to tumorigenesis; however, its function in tumor progression is controversial. This work was undertaken to explore the expression and biological roles of miR-495 in bladder cancer. The expression of miR-495 was examined in 67 pairs of bladder cancer and adjacent normal bladder tissues. The roles of miR-495 in bladder cancer cell proliferation and invasion in vitro and tumorigenesis in vivo were determined. Direct target gene(s) mediating the activity of miR-495 in bladder cancer cells was identified. It was found that miR-495 was expressed at greater levels in bladder tissues and cell lines. High expression of miR-495 was significantly associated with larger tumor size, advanced TNM stage, and lymph node metastasis. Overexpression of miR-495 significantly promoted bladder cancer cell proliferation and invasion, whereas inhibition of miR-495 suppressed cell proliferation and invasion. PTEN, a well-defined tumor suppressor was identified to be a target gene of miR-495. A significant inverse correlation between miR-495 and PTEN expression was noted in bladder cancer tissues (r = -0.3094, P = 0.0125). Overexpression of miR-495 led to reduction of PTEN expression in bladder cancer cells. Rescue experiments showed that enforced expression of PTEN impaired miR-495-mediated bladder cancer proliferation and invasion. In vivo mouse studies demonstrated that overexpression of miR-495 accelerated the growth of subcutaneous bladder cancer xenografts, which was associated with downregulation of PTEN. Overall, these findings indicate that miR-495 upregulation contributes to bladder cancer cell growth, invasion, and tumorigenesis by targeting PTEN and offer a potential therapeutic target for bladder cancer.

MicroRNA target for MACC1 and CYR61 to inhibit tumor growth in mice with colorectal cancer

Cysteine-rich protein 61 (CYR61) and metastasis associated in colon cancer (MACC1) protein promoted human colorectal cancer (CRC) cell metastasis and closely related to the patient's prognosis in colorectal cancer. The purpose of this article is to investigate whether CYR61 and MACC1 can serve as dual potential targets for gene therapy of human CRC. In this study, microRNA (miRNA) targeting for both CYR61 and MACC1 was used to investigate the mechanism and therapeutic effects for CRC cells and mice with CRC. We observed that silencing miRNA for CYR61 and MACC1 inhibited the epithelial-mesenchymal transition (EMT) process, and co-treatment strengthened this effect. MTT assay showed that the growth of colorectal tumor cells was decreased due to miRNA treatment. Apoptosis assay revealed that miRNA for CYR61 and MACC1 promoted CRC cells apoptotic. The animals' study results showed that the expression levels of CYR61 and MACC1 were significantly decreased after miRNA-100 and miRNA-143 treatment, respectively. The expression levels of apoptosis-promoting protein were increased significantly after treatment with miRNA-100 and miRNA-143, which suggested that both miRNA-100 and miRNA-143 may induce apoptosis by mitochondria-dependent pathway. In addition, metastasis and invasion assays showed that miRNA-100 and miRNA-143 treatment inhibited obviously migratory and invasive abilities of CRC cells. Furthermore, our data also showed that the tumor growth was significantly inhibited and survival rate of tumor-bearing mice was greatly improved by common treatments of miRNA-100 and miRNA-143. In conclusion, the abilities of apoptosis, metastasis, and invasion in CRC tumor cells were significantly suppressed by miRNA-100 and miRNA-143 targeting CYR61 and MACC1, respectively. As a result, CYR61 and MACC1 may serve as potential targets for gene therapy in human CRC treatments.

Loss of miR-26a-5p promotes proliferation, migration, and invasion in prostate cancer through negatively regulating SERBP1

The biological role of miR-26a involved in the carcinogenesis of prostate cancer (PC) has been controversial. Besides, the underlying mechanism by which miR-26a plays a role in PC has been unclear. To investigate the role of miR-26a-5p in the PC, miR-26a-5p was detected and statistically analyzed in clinical PC tissues and a panel of PC cell lines. Using bioinformatics analysis, we found that serpine1 messenger RNA (mRNA) binding protein 1 (SERBP1) was a potential downstream target of miR-26a-5p. Using luciferase reporter and western blot, we identified that miR-26a-5p negatively regulated SERBP1 on the PC cell line level. It was confirmed that miR-26a-5p was markedly downregulated in PC tissues compared with normal controls whose reduced expression was significantly associated with metastasis and poor overall prognosis and found that miR-26a-5p was able to prevent proliferation and motility of PC cells in vitro. Additionally, SERBP1 was identified as a downstream target of miR-26a-5p. Moreover, it was observed that SERBP1 was markedly upregulated in prostate cancer tissues and was significantly associated with tissue metastasis and Gleason score. Taken together, our results for the first time demonstrate that the loss of miR-26a-5p promotes proliferation, migration, and invasion through targeting SERBP1 in PC, supporting the tumor-suppressing role of miR-26a-5p in PC.