MicroRNA-206: Effective Inhibition of Gastric Cancer Progression through the c-Met Pathway

Research progress on the development of hepatocyte growth factor/c-Met signaling pathway in gastric cancer: A review

Hepatocyte growth factor (HGF) and its receptor, c-Met, play important roles in the occurrence, development, and treatment of gastric cancer (GC). This review explored the function of the HGF/c-Met signaling pathway in GC and its potential targeted therapeutic mechanisms. As one of the most common malignant tumors worldwide, GC has a complex pathogenesis and limited therapeutic options. Therefore, a thorough understanding of the molecular mechanism of GC is very important for the development of new therapeutic methods. The HGF/c-Met signaling pathway plays an important role in the proliferation, migration, and invasion of GC cells and has become a new therapeutic target. This review summarizes the current research progress on the role of HGF/c-Met in GC and discusses targeted therapeutic strategies targeting this signaling pathway, providing new ideas and directions for the treatment of GC.

Ferroptosis regulating lipid peroxidation metabolism in the occurrence and development of gastric cancer

BACKGROUND

Gastric cancer is one of the most common malignant tumors in the world, and its occurrence and development involve complex biological processes. Iron death, as a new cell death mode, has attracted wide attention in recent years. However, the regulatory mechanism of iron death in gastric cancer and its effect on lipid peroxidation metabolism remain unclear.

AIM

To explore the role of iron death in the development of gastric cancer, reveal its relationship with lipid peroxidation, and provide a new theoretical basis for revealing the molecular mechanism of the occurrence and development of gastric cancer.

METHODS

The process of iron death in gastric cancer cells was simulated by cell culture model, and the occurrence of iron death was detected by fluorescence microscopy and flow cytometry. The changes of gene expression related to iron death and lipid peroxidation metabolism were analyzed by high-throughput sequencing technology. In addition, a mouse model of gastric cancer was established, and the role of iron death in vivo was studied by histology and immunohistochemistry, and the level of lipid peroxidation was detected. These methods comprehensively and deeply reveal the regulatory mechanism of iron death on lipid peroxidation metabolism in the occurrence and development of gastric cancer.

RESULTS

Iron death was significantly activated in gastric cancer cells, and at the same time, associated lipid peroxidation levels increased significantly. Through high-throughput sequencing analysis, it was found that iron death regulated the expression of several genes related to lipid metabolism. In vivo experiments demonstrated that increased iron death in gastric cancer mice was accompanied by a significant increase in lipid peroxidation.

CONCLUSION

This study confirmed the important role of iron death in regulating lipid peroxidation metabolism in the occurrence and development of gastric cancer. The activation of iron death significantly increased lipid peroxidation levels, revealing its regulatory mechanism inside the cell.

Non-coding RNAs as potential therapeutic targets for receptor tyrosine kinase signaling in solid tumors: current status and future directions

This review article presents an in-depth analysis of the current state of research on receptor tyrosine kinase regulatory non-coding RNAs (RTK-RNAs) in solid tumors. RTK-RNAs belong to a class of non-coding RNAs (nc-RNAs) responsible for regulating the expression and activity of receptor tyrosine kinases (RTKs), which play a critical role in cancer development and progression. The article explores the molecular mechanisms through which RTK-RNAs modulate RTK signaling pathways and highlights recent advancements in the field. This include the identification of potential new RTK-RNAs and development of therapeutic strategies targeting RTK-RNAs. While the review discusses promising results from a variety of studies, encompassing in vitro, in vivo, and clinical investigations, it is important to acknowledge the challenges and limitations associated with targeting RTK-RNAs for therapeutic applications. Further studies involving various cancer cell lines, animal models, and ultimately, patients are necessary to validate the efficacy of targeting RTK-RNAs. The specificity of ncRNAs in targeting cellular pathways grants them tremendous potential, but careful consideration is required to minimize off-target effects, the article additionally discusses the potential clinical applications of RTK-RNAs as biomarkers for cancer diagnosis, prognosis, and treatment. In essence, by providing a comprehensive overview of the current understanding of RTK-RNAs in solid tumors, this review emphasizes their potential as therapeutic targets for cancer while acknowledging the associated challenges and limitations.

Interaction between miR‑206 and lncRNA MALAT1 in regulating viability and invasion in hepatocellular carcinoma

MicroRNAs (miRNAs) are strongly associated to the progression of hepatocellular carcinoma (HCC), which presents a high potential for diagnosis and treatment; however, the role of miRNAs is still largely unknown. The aim of the present study was to examine the expression and the biological role of miRNA (miR)-206 in the development of HCC, and to identify the underlying molecular mechanism. Results from this study show that miR-206 was significantly downregulated in HCC tissues and cell lines. It was observed that low expression of miR-206 was linked to advanced TNM stage, tumor nodularity and venous infiltration in patients with HCC; low miR-206 expression was associated with shorter survival times. miR-206 overexpression using miR-206 mimics notably decreased the proliferative ability and increased apoptosis of MHCC97-H and HCCLM3 HCC cell lines. Overexpression of miR-206 suppressed invasiveness associated with reduced epithelial-mesenchymal transition. Moreover, the c-Met oncogene, which is upregulated in HCC tissues, was negatively associated with the expression of miR-206. Notably, it was shown that miR-206 may exert its antitumor effect through suppressing c-Met/Akt/mTOR signaling. Low expression of miR-206 was shown to be regulated by lncRNA MALAT1 in HCC. Collectively, this study presented evidence that miR-206 was controlled by lncRNA MALAT1 and partially suppressed the proliferation and invasion of HCC through the c-Met/Akt/mTOR signaling pathway. According to these results, understanding MALAT1/miR-206-dependent regulation may lead to potential approaches for diagnosis and prospective treatment of HCC.

Integrated pan-cancer analysis and experimental verification of the roles of tropomyosin 4 in gastric cancer

Objective

To investigate the function of tropomyosin 4 (TPM4) using pan-cancer data, especially in gastric cancer (GC), using comprehensive bioinformatics analysis and molecular experiments.

Methods

We used UCSC Xena, The Cancer Genome Atlas (TCGA), Genotype-Tissue Expression Project (GTEx), TIMER2.0, GEPIA, cBioPortal, Xiantao tool, and UALCAN websites and databases for the extraction of pan-cancer data on TPM4. TPM4 expression was investigated with respect to prognosis, genetic alterations, epigenetic alterations, and immune infiltration. RNA22, miRWalk, miRDB, Starbase 2.0, and Cytoscape were used for identifying and constructing the regulatory networks of lncRNAs, miRNAs, and TPM4 in GC. Data from GSCALite, drug bank databases, and Connectivity Map (CMap) were used to analyze the sensitivity of drugs dependent on TPM4 expression. Gene Ontology (GO), enrichment analyses of the Kyoto Encyclopedia of Genes and Genomes (KEGG), wound healing assays, and (Matrigel) transwell experiments were used to investigate the biological functions of TPM4 in GC.

Result

The findings of the comprehensive pan-cancer analysis revealed that TPM4 has a certain diagnostic and prognosis value in most cancers. Alterations in the expression of TPM4, including duplications and deep mutations, and epigenetic alterations revealed that TPM4 expression is related to the expression of DNA methylation inhibitors and RNA methylation regulators at high concentrations. Besides, TPM4 expression was found to correlate with immune cell infiltration, immune checkpoint (ICP) gene expression, the tumor mutational burden (TMB), and microsatellite instability (MSI). Neoantigens (NEO) were also found to influence its response to immunotherapy. A lncRNA-miRNA -TPM4 network was found to regulate GC development and progression. TPM4 expression was related to docetaxel,5-fluorouracil, and eight small molecular targeted drugs sensitivity. Gene function enrichment analyses revealed that genes that were co-expressed with TPM4 were enriched within the extracellular matrix (ECM)-related pathways. Wound-healing and (Matrigel) transwell assays revealed that TPM4 promotes cell migration and invasion. TPM4, as an oncogene, plays a biological role, perhaps via ECM remodeling in GC.

Conclusions

TPM4 is a prospective marker for the diagnosis, treatment outcome, immunology, chemotherapy, and small molecular drugs targeted for pan-cancer treatment, including GC treatment. The lncRNA-miRNA-TPM4network regulates the mechanism underlying GC progression. TPM4 may facilitate the invasion and migration of GC cells, possibly through ECM remodeling.

Crizotinib-based proteolysis targeting chimera suppresses gastric cancer by promoting MET degradation

As one of the common malignant cancer types, gastric cancer (GC) is known for late-stage diagnosis and poor prognosis. Overexpression of the receptor tyrosine kinase MET is associated with poor prognosis among patients with advanced stage GC. However, no MET inhibitor has been used for GC treatment. Like other tyrosine kinase inhibitors that fit the "occupancy-driven" model, current MET inhibitors are prone to acquired resistance. The emerging proteolysis targeting chimera (PROTAC) strategy could overcome such limitations through direct degradation of the target proteins. In this study, we successfully transformed the MET-targeted inhibitor crizotinib into a series of PROTACs, recruiting cereblon/cullin 4A E3 ubiquitin ligase to degrade the MET proteins. The optimized lead PROTAC (PRO-6 E) effectively eliminated MET proteins in vitro and in vivo, inhibiting proliferation and motility of MET-positive GC cells. In the MKN-45 xenograft model, PRO-6 E showed pronounced antitumor efficacy with a well-tolerated dosage regimen. These results validated PRO-6 E as the first oral PROTAC for MET-dependent GC.

Integrative Analysis of miRNAs Involved in Fat Deposition in Different Pig Breeds

BACKGROUND

miRNAs are a set of small, noncoding RNAs that bind to partially complementary sequences on target mRNAs. This leads to the post-transcriptional regulation of gene expression. Many studies have shown that microRNAs play critical roles in adipose cell differentiation and fat metabolism. The aim of this study was to explore the regulatory functions of miRNAs in fat deposition for the prevention and therapy of lipid metabolism-related diseases.

METHODS

The significant differences in the fat deposition of Laiwu (LW) pigs and Large White (LY) pigs were studied. To investigate the genetic relationships of miRNAs that regulate fat deposition, we performed a genome-wide analysis of miRNAs derived from subcutaneous adipose tissue of LW and LY pigs using RNA-seq.

RESULTS

There were 39 known miRNAs and 56 novel miRNAs significantly differential expressed between the two breeds of pigs. In the analysis of the Gene Ontology and KEGG pathways, predicted targets of these differentially expressed miRNAs were involved in several fat-associated pathways, such as the peroxisome proliferator-activated receptor (PPAR), mitogen-activated protein kinases (MAPK) and Wnt signaling pathways. In addition, ssc-miR-133a-3p, ssc-miR-486 and ssc-miR-1 each had a great impact on the development of porcine subcutaneous fat through the PPAR signaling pathway.

CONCLUSIONS

We explored the role of differentially expressed miRNAs and studied the mechanisms of adipogenesis and fat deposition between two different pig breeds. In addition, these results also contribute to research relevant to human obesity.

c-Met: A Promising Therapeutic Target in Bladder Cancer

Mesenchymal-epithelial transition factor (c-Met) belongs to the tyrosine kinase receptor family and is overexpressed in various human cancers. Its ligand is hepatocyte growth factor (HGF), and the HGF/c-Met signaling pathway is involved in a wide range of cellular processes, including cell proliferation, migration, and metastasis. Emerging studies have indicated that c-Met expression is strongly associated with bladder cancer (BCa) development and prognosis. Therefore, c-Met is a potential therapeutic target for BCa treatment. Recently, the aberrant expression of noncoding RNAs was found to play a significant role in tumour progression. There is a close connection between c-Met and noncoding RNA. Herein, we summarized the biological function and prognostic value of c-Met in BCa, as well as its potential role as a drug target. The relation of c-Met and ncRNA was also described in the paper.

miR-206 regulates non-small-cell lung cancer cell aerobic glycolysis by targeting hexokinase 2

Aerobic glycolysis was closely associated with the malignant transformation and prognosis of tumours. miR-206 was found to be downregulated in several cancers. However, whether miR-206 functions in non-small-cell lung cancers (NSCLCs) via the process of aerobic glycolysis remains poorly characterized. Quantitative real-time PCR was performed to detect miR-206 level in NSCLC cells and tissues. The effect of miR-206 on hexokinase 2 (HK2) expression was examined through miR-206 overexpression or miR-206 knockdown. CCK-8 assay and colony formation assay were carried out to explore the role of miR-206 on cell proliferation and colony formation, respectively. The relationship between miR-206 and HK2 was measured by dual-luciferase reporter assay. Glucose consumption, lactate production assay and ATP generation were performed in NSCLC cells following miR-206 and HK2 overexpression. We found that miR-206 was downregulated in NSCLC tissues and cells. miR-206 overexpression downregulated the expression of HK2 via targeting HK2 3'UTR in NSCLC cells. In addition, miR-206 decreased the cell viability and colony formation in NSCLC cells. Furthermore, miR-206 reduced glucose uptake, lactate production and ATP generation in NSCLC cells via HK2 repression. In conclusion, these findings suggested that miR-206 regulated NSCLC cell aerobic glycolysis by targeting HK2.

MET Inhibitors for the Treatment of Gastric Cancer: What's Their Potential?

Gastric cancer remains a disease with a dismal prognosis. Extensive efforts to find targetable disease drivers in gastric cancer were implemented to improve patient outcomes. Beyond anti-HER2 therapy, MET pathway seems to be culprit of cancer invasiveness with MET-overexpressing tumors having poorer prognosis. Tyrosine kinase inhibitors targeting the HGF/MET pathway were studied in MET-positive gastric cancer, but no substantial benefit was proven. Some patients responded in early phase trials but later developed resistance. Others failed to show any benefit at all. Etiologies of resistance may entail inappropriate patient selection with a lack of MET detection standardization, tumor alternative pathways, variable MET amplification, and genetic variation. Optimizing MET detection techniques and better understanding the MET pathway, as well as tumor bypass mechanisms, are an absolute need to devise means to overcome resistance using targeted therapy alone, or in combination with other synergistic agents to improve outcomes of patients with MET-positive GC.

Targeting the HGF/MET Axis in Cancer Therapy: Challenges in Resistance and Opportunities for Improvement

Among hundreds of thousands of signal receptors contributing to oncogenic activation, tumorigenesis, and metastasis, the hepatocyte growth factor (HGF) receptor - also called tyrosine kinase MET - is a promising target in cancer therapy as its axis is involved in several different cancer types. It is also associated with poor outcomes and is involved in the development of therapeutic resistance. Several HGF/MET-neutralizing antibodies and MET kinase-specific small molecule inhibitors have been developed, resulting in some context-dependent progress in multiple cancer treatments. Nevertheless, the concomitant therapeutic resistance largely inhibits the translation of such targeted drug candidates into clinical application. Until now, numerous studies have been performed to understand the molecular, cellular, and upstream mechanisms that regulate HGF/MET-targeted drug resistance, further explore novel strategies to reduce the occurrence of resistance, and improve therapeutic efficacy after resistance. Intriguingly, emerging evidence has revealed that, in addition to its conventional function as an oncogene, the HGF/MET axis stands at the crossroads of tumor autophagy, immunity, and microenvironment. Based on current progress, this review summarizes the current challenges and simultaneously proposes future opportunities for HGF/MET targeting for therapeutic cancer interventions.

miR-206 inhibits liver cancer stem cell expansion by regulating EGFR expression

Liver cancer stem cells (CSCs) are involved in tumorigenesis, progression, drug resistance and recurrence of hepatocellular carcinoma (HCC). However, the underlying mechanism for the propagation of liver cancer stem cells was unclear. Herein, we observed miR-206 expression was reduced in both chemoresistant HCCs and recurrent HCCs from patients. A dramatically decrease of miR-206 was detected in cluster of differentiation 133 (CD133) or epithelial cell adhesion molecule (EpCAM)-positive liver CSCs and in CSC-enriched hepatoma spheres. Functional studies revealed that a forced expression of miR-206 inhibited liver CSCs expansion by suppressing the dedifferentiation of hepatoma cells and attenuating the self-renewal of liver CSCs. Mechanistically, bioinformatic and luciferase reporter analysis identified epidermal growth factor receptor (EGFR) as a direct target of miR-206. Moreover, miR-206 downregulated the expression of EGFR in liver CSCs. There was a significant inverse correlation between miR-206 and EGFR mRNA expression in HCC samples. Special EGFR inhibitor Gefitinib abolished the discrepancy in liver CSC proportion and the self-renewal capacity between miR-206 overexpression hepatoma cells and control cells, which further confirmed that EGFR was required in miR-206-inhibited liver CSCs expansion. Conclusion: miR-206 could suppress HCC cell dedifferentiation and liver CSCs expansion by targeting EGFR signaling.

MicroRNAs and Long Non-coding RNAs in c-Met-Regulated Cancers

MicroRNAs (miRNAs) and long non-coding RNAs (lncRNAs) are components of many signaling pathways associated with tumor aggressiveness and cancer metastasis. Some lncRNAs are classified as competitive endogenous RNAs (ceRNAs) that bind to specific miRNAs to prevent interaction with target mRNAs. Studies have shown that the hepatocyte growth factor/mesenchymal-epithelial transition factor (HGF/c-Met) pathway is involved in physiological and pathological processes such as cell growth, angiogenesis, and embryogenesis. Overexpression of c-Met can lead to sustained activation of downstream signals, resulting in carcinogenesis, metastasis, and resistance to targeted therapies. In this review, we evaluated the effects of anti-oncogenic and oncogenic non-coding RNAs (ncRNAs) on c-Met, and the interactions among lncRNAs, miRNAs, and c-Met in cancer using clinical and tissue chromatin immunoprecipition (ChIP) analysis data. We summarized current knowledge of the mechanisms and effects of the lncRNAs/miR-34a/c-Met axis in various tumor types, and evaluated the potential therapeutic value of lncRNAs and/or miRNAs targeted to c-Met on drug-resistance. Furthermore, we discussed the functions of lncRNAs and miRNAs in c-Met-related carcinogenesis and potential therapeutic strategies.

Crosstalk Mechanisms Between HGF/c-Met Axis and ncRNAs in Malignancy

Several lines of evidence have confirmed the magnitude of crosstalk between HGF/c-Met axis (hepatocyte growth factor and its high-affinity receptor c-mesenchymal-epithelial transition factor) and non-coding RNAs (ncRNAs) in tumorigenesis. Through activating canonical or non-canonical signaling pathways, the HGF/c-Met axis mediates a range of oncogenic processes such as cell proliferation, invasion, apoptosis, and angiogenesis and is increasingly becoming a promising target for cancer therapy. Meanwhile, ncRNAs are a cluster of functional RNA molecules that perform their biological roles at the RNA level and are essential regulators of gene expression. The expression of ncRNAs is cell/tissue/tumor-specific, which makes them excellent candidates for cancer research. Many studies have revealed that ncRNAs play a crucial role in cancer initiation and progression by regulating different downstream genes or signal transduction pathways, including HGF/c-Met axis. In this review, we discuss the regulatory association between ncRNAs and the HGF/c-Met axis by providing a comprehensive understanding of their potential mechanisms and roles in cancer development. These findings could reveal their possible clinical applications as biomarkers for therapeutic interventions.

An overview of the multifaceted roles of miRNAs in gastric cancer: Spotlight on novel biomarkers and therapeutic targets

MicroRNAs (miRNAs) are a group of small non-coding RNAs that have displayed strong association with gastric cancer (GC). Through the repression of target mRNAs, miRNAs regulate many biological pathways that are involved in cell proliferation, apoptosis, migration, invasion, metastasis as well as drug resistance. The detection of miRNAs in tissues and in body fluids emerges as a promising method in the diagnosis and prognosis of GC, due to their unique expression pattern in correlation with GC. Notably, miRNAs are also identified as potential therapeutic targets for GC therapy. The present review is thus to highlight the multifaceted roles of miRNAs in GC and in GC therapies, which would give indications for future research.

The long non-coding RNA-ROR promotes osteosarcoma progression by targeting miR-206

The long intergenic non-protein coding RNA regulator of reprogramming (lncRNA-ROR) has been reported to play crucial regulatory roles in the pathogenesis and progression of multiple cancers. However, whether ROR is associated with the initiation and development of osteosarcoma (OS) remains unclear. Here, we found that ROR expression level was significantly up-regulated in OS tissue samples compared to adjacent normal tissues, and the elevated ROR was closely correlated with advanced tumour-node-metastasis (TNM) stage and lymph node metastasis and poor overall survival rate. Functional assays showed that ROR knockdown suppressed the OS cell proliferation, colony formation, migration and invasion in vitro, and retarded tumour growth in vivo. In addition, miR-206 was verified to be a target miRNA of ROR using bioinformatics online program and luciferase report assay. miR-206 inhibition partially rescued the inhibitory effects on OS cells induced by ROR knockdown. In conclusion, these results suggested that ROR function as an oncogene in OS by sponging miR-206 and might be a potential therapeutic target for patients with OS.

Retracted Article: MiR-206 reduced the malignancy of hepatocellular carcinoma cells in vitro by inhibiting MET and CTNNB1 gene expressions

The anti-cancer role of miR-206 in hepatocellular carcinoma (HCC) cells has been reported, but its mechanism of action remains poorly understood.

LncRNA RMRP silence curbs neonatal neuroblastoma progression by regulating microRNA-206/tachykinin-1 receptor axis via inactivating extracellular signal-regulated kinases

BACKGROUND

Neuroblastoma is the commonest malignancy in neonates. Long non-coding RNA (lncRNA) RNA component of mitochondrial RNA processing endoribonuclease (RMRP) has been reported to be an oncogenic factor in some malignancies. However, its roles and molecular mechanisms in neuroblastoma progression are poor defined.

METHODS

The expression of RMRP, microRNA-206 (miR-206), and tachykinin-1 receptor (TACR1) mRNA was measured by RT-qPCR assay. Protein levels of TACR1, phosphorylated extracellular signal-regulated kinases (ERK) 1/2 (p-ERK1/2) and ERK1/2 were detected by western blot assay. Cell proliferation was assessed by CCK-8 and colony formation assays. Cell migratory and invasive capacities were determined using Transwell migration and invasion assays. The interaction between miR-206 and RMRP or TACR1 was verified by luciferase assay. The roles and molecular mechanisms of RMRP knockdown on the growth of neuroblastoma xenografts were examined in vivo.

RESULTS

RMRP was highly expressed in neuroblastoma tissues. RMRP knockdown inhibited proliferation, migration and invasion in neuroblastoma cells. Moreover, TACR1 was a target of miR-206 and RMRP performed as a molecular sponge of miR-206 to sequester miR-206 from TACR1 in neuroblastoma cells. TACR1 overexpression abrogated the inhibitory effect of RMRP downregulation on neuroblastoma cell progression by activating ERK1/2 pathway. Inhibition of TACR1 and ERK1/2 pathway abated RMRP-mediated pro-proliferation effect in neuroblastoma cells. RMRP knockdown hindered neuroblastoma xenograft growth by regulating miR-206/TACR1 axis via inactivating ERK1/2 pathway in vivo.

CONCLUSION

RMRP knockdown hindered the tumorigenesis and progression of neuroblastoma by regulating miR-206/TACR1 axis via inactivating ERK1/2 pathway, hinting a potential therapeutic target for neuroblastoma.

HGF/c-MET: A Promising Therapeutic Target in the Digestive System Cancers

The HGF/c-MET pathway is active in the development of digestive system cancers, indicating that inhibition of HGF/c-MET signaling may have therapeutic potential. Various HGF/c-MET signaling inhibitors, mainly c-MET inhibitors, have been tested in clinical trials. The observed efficacy and adverse events of some c-MET inhibitors were not very suitable for treating digestive system cancers. The development of new HGF/c-MET inhibitors in preclinical studies may bring promising treatments and synergistic combination (traditional anticancer drugs and c-MET inhibitors) strategies provided anacceptable safety and tolerability. Insights into miRNA biology and miRNA therapeutics have made miRNAs attractive tools to inhibit HGF/c-MET signaling. Recent reports show that several microRNAs participate in inhibiting HGF/c-MET signaling networks through antagonizing c-MET or HGF in digestive system cancers, and the miRNAs-HGF/c-MET axis plays crucial and novel roles for cancer treatment. In the current review, we will discuss recent findings about inhibitors of HGF/c-MET signaling in treating digestive system cancers, and how miRNAs regulate digestive system cancers via mediating HGF/c-MET pathway.

Circ_0056618 and CXCR4 act as competing endogenous in gastric cancer by regulating miR-206

Circular RNAs (circRNAs) have proved to play an important role in gastric cancer. In this study, we found that circ_0056618 took part in gastric cancer cell proliferation and survival. The real-time polymerase chain reaction result showed that circ_0056618 was overexpressed in tumor tissues or cells compared with adjacent normal tissues or normal cells and had a negative relationship to gastric cancer patients' survival time. Meanwhile, the inhibition of circ_0056618 suppressed the proliferation and metastasis of gastric cancer cells. Further bioinformatical analysis indicated that circ_0056618 sponged miR-206 to regulate CXCR4 according to the prediction of TargetScan and miRanda. Dual-luciferase reporter assay and Western blot analysis revealed the underlying relationship of circ_0056618, miR-206, and CXCR4. Hence, circ_0056618 negatively regulated miR-206 expression promoting CXCR4 expression. Altogether, circ_0056618 is a potential gastric cancer prognostic marker, as well as a potential therapeutic target to inhibit gastric cancer metastasis.

Cigarette smoke enhances oncogene addiction to c-MET and desensitizes EGFR-expressing non-small cell lung cancer to EGFR TKIs

Cigarette smoking is one of the leading risks for lung cancer and is associated with the insensitivity of non‐small cell lung cancer (NSCLC) to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs). However, it remains undetermined whether and how cigarette smoke affects the therapeutic efficacy of EGFR TKIs. In this study, our data showed that chronic exposure to cigarette smoke extract (CSE) or tobacco smoke‐derived carcinogen benzo[α]pyrene, B[α]P, but not nicotine‐derived nitrosamine ketone (NNK), reduced the sensitivity of wild‐type EGFR‐expressing NSCLC cells to EGFR TKIs. Treatment with TKIs almost abolished EGFR tyrosine kinase activity but did not show an inhibitory effect on downstream Akt and ERK pathways in B[α]P‐treated NSCLC cells. CSE and B[α]P transcriptionally upregulate c‐MET and activate its downstream Akt pathway, which is not inhibited by EGFR TKIs. Silencing of c‐MET reduces B[α]P‐induced Akt activation. The CSE‐treated NSCLC cells are sensitive to the c‐MET inhibitor crizotinib. These findings suggest that cigarette smoke augments oncogene addiction to c‐MET in NSCLC cells and that MET inhibitors may show clinical benefits for lung cancer patients with a smoking history.

miR‑206 inhibits cancer initiating cells by targeting EHF in gastric cancer

Cancer initiating cells (CIC) are defined as the unique subpopulation in the tumors that possess the ability to initiate tumor growth and sustain self-renewal as well as metastatic potential. In this study, we found that EHF overexpression promoted formation of CIC traits and silencing it inhibited the traits in gastric cancer NCI‑N87 cells. Overexpressing EHF downregulated the antitumor effect of 5-fluorouracil (5-FU) in NCI‑N87 cells. We found that miR‑206 downregulated EHF protein expression by targeting its 3'UTR in NCI‑N87 cells and GES-1 cells. Overexpressing miR‑206 inhibited formation of CIC in NCI‑N87 cells. In gastric cancer tissues, EHF protein expression was upregulated and miR‑206 was downregulated. We identified a negative correlation between EHF protein and miR‑206 expression in gastric cancer tissues. Thus, we concluded that miR‑206 inhibits formation of CICs by targeting EHF in gastric cancer.

The diagnostic and prognostic value of serum miR-206 in colorectal cancer

Circulating microRNAs (miRNAs) are emerging as promising biomarkers for colorectal cancer (CRC). In this study, we sought to examine the diagnostic and prognostic role of serum miR-206 in CRC. A total of 73 CRC cases and 45 healthy control subjects were enrolled in this study. Quantitative reverse transcription PCR (qRT-PCR) was used to measure the relative serum miR-206 levels. Serum miR-206 levels were significantly decreased in CRC patients than normal controls. In addition, serum miR-206 demonstrated good diagnostic performance for discriminating CRC patients from healthy controls. miR-206 levels were increased in the blood samples of CRC patients who received surgery treatment. Moreover, serum miR-206 expression was closely associated with TNM stage and lymph node metastasis. CRC patients with low miR-206 level suffered more unfavorable overall survival and disease free survival compared to those with high miR-206 level. Furthermore, serum miR-206 was confirmed to be an independent prognostic indicator for CRC. In summary, serum miR-206 might be a promising biomarker for the diagnosis and prognosis of CRC.

MiR-206 inhibits HGF-induced epithelial-mesenchymal transition and angiogenesis in non-small cell lung cancer via c-Met /PI3k/Akt/mTOR pathway

MiR-206 is low expression in lung cancers and associated with cancer metastasis. However, the roles of miR-206 in epithelial-mesenchymal transition (EMT) and angiogenesis in lung cancer remain unknown. In this study, we find that hepatocyte growth factor (HGF) induces EMT, invasion and migration in A549 and 95D lung cancer cells, and these processes could be markedly inhibited by miR-206 overexpression. Moreover, we demonstrate that miR-206 directly targets c-Met and inhibits its downstream PI3k/Akt/mTOR signaling pathway. In contrast, miR-206 inhibitors promote the expression of c-Met and activate the PI3k/Akt/mTOR signaling, and this effect could be attenuated by the PI3K inhibitor. Moreover, c-Met overexpression assay further confirms the significant inhibitory effect of miR-206 on HGF-induced EMT, cell migration and invasion. Notably, we also find that miR-206 effectively inhibits HGF-induced tube formation and migration of human umbilical vein endothelial cells (HUVECs), and the mechanism is also related to inhibition of PI3k/Akt/mTOR signaling. Finally, we reveal the inhibitory effect of miR-206 on EMT and angiogenesis in xenograft tumor mice model. Taken together, miR-206 inhibits HGF-induced EMT and angiogenesis in lung cancer by suppressing c-Met/PI3k/Akt/mTOR signaling. Therefore, miR-206 might be a potential target for the therapeutic strategy against EMT and angiogenesis of lung cancer.

Insights into roles of the miR-1, -133 and -206 family in gastric cancer (Review)

Gastric cancer (GC) remains the third most common cause of cancer deaths worldwide and carries a high rate of metastatic risk contributing to the main cause of treatment failure. An accumulation of data has resulted in a better understanding of the molecular network of GC, however, gaps still exist between the unique bio-resources and clinical application. MicroRNAs are an important part of non-coding RNAs and behave as major regulators of tumour biology, alongside their well-known roles as intrinsic factors of gene expression in cellular processes, via their post-transcriptional regulation of components of signalling pathways in a coordinated manner. Deregulation of the miR-1, -133 and -206 family plays a key role in tumorigenesis, progression, invasion and metastasis. This review aims to provide a summary of recent findings on the miR-1, -133 and -206 family in GC and how this knowledge might be exploited for the development of future miRNA-based therapies for the treatment of GC.

microRNA-206 is involved in survival of hypoxia preconditioned mesenchymal stem cells through targeting Pim-1 kinase

Background

Overexpression of Pim-1 in stem/progenitor cells stimulated cell cycling and enhanced cardiac regeneration in vivo. We proposed that hypoxic preconditioning could increase survival of bone marrow mesenchymal stem cells (MSCs) via upregulation of Pim-1 and aimed to determine the microRNAs that modulate the expression of Pim-1.

Methods and results

MSCs were subjected to hypoxia exposure. The expression of Pim-1 in MSCs was enhanced in a time-dependent manner, detected by quantitative PCR and western blot. miR-206 is predicted as one of the potential microRNAs that target Pim-1. The expression of miR-206 was decreased in hypoxic MSCs and reversely correlated with Pim-1 expression. Luciferase activity assay further confirmed Pim-1 as a putative target of miR-206. In addition, gain and loss-of-function studies with miR-206 mimics and inhibitors showed that inhibition of miR-206 in hypoxic MSCs promoted the migration ability of the cells, prevented cell apoptosis, and protected membrane potential of mitochondria, while the benefits were all blocked by Pim-1 inhibitor. In an acute model of myocardial infarction, transplanted hypoxic MSCs showed a significantly improved survival as compared with hypoxic MSCs overexpressing miR-206.

Conclusions

Hypoxic preconditioning could increase short-term survival of bone marrow MSCs via upregulation of Pim-1, and miR-206 was one of the critical regulators in this process.

Tissue microRNAs as predictive markers for gastric cancer patients undergoing palliative chemotherapy

MicroRNAs have the potential to become valuable predictive markers for gastric cancer. Samples of biopsy tissue, routinely taken from gastric cancer patients undergoing palliative chemotherapy, constitute suitable material for microRNA profiling with the aim of predicting the effect of chemotherapy. Our study group consisted of 54 patients, all of whom underwent palliative chemotherapy based on 5-fluorouracil (5-FU) or 5-FU in combination with platinum derivatives between 2000 and 2013. The expression of 29 selected microRNAs and genes BRCA1, ERCC1, RRM1 and TS, in gastric cancer tissue macrodissected from FFPE tissue samples, was measured by quantitative RT-PCR. The relationship between gene expression levels and time to progression (TTP) and overall survival (OS) was analysed. From the set of the 29 microRNAs of interest, we found high expression of miR-150, miR-342-3p, miR-181b, miR-221, miR-224 and low levels of miR-520h relate to shorter TTP. High levels of miR-150, miR-192, miR-224, miR-375 and miR-342-3p related to shorter OS. In routinely available FFPE tissue samples, we found 6 miRNAs with a relation to TTP, which may serve as predictors of the effectiveness of palliative treatment in gastric cancer patients. These miRNAs could also help in deciding whether to indicate palliative chemotherapy.