Reexpression of Let-7g microRNA inhibits the proliferation and migration via K-Ras/HMGA2/snail axis in hepatocellular carcinoma

Factors Determining Epithelial-Mesenchymal Transition in Cancer Progression

Epithelial-mesenchymal transition (EMT) is a process in which an epithelial cell undergoes multiple modifications, acquiring both morphological and functional characteristics of a mesenchymal cell. This dynamic process is initiated by various inducing signals that activate numerous signaling pathways, leading to the stimulation of transcription factors. EMT plays a significant role in cancer progression, such as metastasis and tumor heterogeneity, as well as in drug resistance. In this article, we studied molecular mechanisms, epigenetic regulation, and cellular plasticity of EMT, as well as microenvironmental factors influencing this process. We included both in vivo and in vitro models in EMT investigation and clinical implications of EMT, such as the use of EMT in curing oncological patients and targeting its use in therapies. Additionally, this review concludes with future directions and challenges in the wide field of EMT.

Research Progress of Aging-related MicroRNAs

Senescence refers to the irreversible state in which cells enter cell cycle arrest due to internal or external stimuli. The accumulation of senescent cells can lead to many age-related diseases, such as neurodegenerative diseases, cardiovascular diseases, and cancers. MicroRNAs are short non-coding RNAs that bind to target mRNA to regulate gene expression after transcription and play an important regulatory role in the aging process. From nematodes to humans, a variety of miRNAs have been confirmed to alter and affect the aging process. Studying the regulatory mechanisms of miRNAs in aging can further deepen our understanding of cell and body aging and provide a new perspective for the diagnosis and treatment of aging-related diseases. In this review, we illustrate the current research status of miRNAs in aging and discuss the possible prospects for clinical applications of targeting miRNAs in senile diseases.

Let-7g Upregulation Attenuated the KRAS-PI3K-Rac1-Akt Axis-Mediated Bioenergetic Functions

The aberrant activation of signaling pathways contributes to cancer cells with metabolic reprogramming. Thus, targeting signaling modulators is considered a potential therapeutic strategy for cancer. Subcellular fractionation, coimmunoprecipitation, biochemical analysis, and gene manipulation experiments revealed that decreasing the interaction of kirsten rat sarcoma viral oncogene homolog (KRAS) with p110α in lipid rafts with the use of naringenin (NGN), a citrus flavonoid, causes lipid raft-associated phosphatidylinositol 3-kinase (PI3K)-GTP-ras-related C3 botulinum toxin substrate 1 (Rac1)-protein kinase B (Akt)-regulated metabolic dysfunction of glycolysis and mitochondrial oxidative phosphorylation (OXPHOS), leading to apoptosis in human nasopharyngeal carcinoma (NPC) cells. The use of lethal-7g (let-7g) mimic and let-7g inhibitor confirmed that elevated let-7g resulted in a decrease in KRAS expression, which attenuated the PI3K-Rac1-Akt-BCL-2/BCL-xL-modulated mitochondrial energy metabolic functions. Increased let-7g depends on the suppression of the RNA-specificity of monocyte chemoattractant protein-induced protein-1 (MCPIP1) ribonuclease since NGN specifically blocks the degradation of pre-let-7g by NPC cell-derived immunoprecipitated MCPIP1. Converging lines of evidence indicate that the inhibition of MCPIP1 by NGN leads to let-7g upregulation, suppressing oncogenic KRAS-modulated PI3K-Rac1-Akt signaling and thereby impeding the metabolic activities of aerobic glycolysis and mitochondrial OXPHOS.

MicroRNA Associated with the Invasive Phenotype in Clear Cell Renal Cell Carcinoma: Let-7c-5p Inhibits Proliferation, Migration, and Invasion by Targeting Insulin-like Growth Factor 1 Receptor

Differential microRNA (miRNA) expression can portend clear cell renal cell carcinoma (ccRCC) progression. In a previous study, we identified a subset of dysregulated miRNA in small renal masses, pT1 ccRCC (≤5 cm) that are associated with an aggressive phenotype. The present study investigated miRNA expression in clinical stage I (cT1) tumors (≤5 cm), comparing pathologic stage I (pT1) tumors to those upstaged to pathologic stage 3 (pT3) after surgery following identification of renal vein invasion or invasion into adjacent fat tissue within Gerota’s fascia. Twenty cT1 tumors were examined in an miRNA screening, 10 pT1 and 10 pT3 tumors. The ccRCC cell lines 786-O and Caki-1 were used to assess the impact of let-7c-5p and its protein target insulin-like growth factor 1 receptor (IGF1R). Cells were transfected with pre-let-7c-5p and assessed through cell proliferation, migration, and invasion assays. IGF1R expression was evaluated through Simple Western, and interaction between let-7c-5p and IGF1R was confirmed via luciferase reporter assay. Screening identified 20 miRNA, including let-7c-5p, that were dysregulated between pT1 and pT3 upstaged tumors. This miRNA was also downregulated in our previous study of pT1 tumors that progressed to metastatic disease. Transfection of ccRCC cells with pre-let-7c-5p significantly inhibited proliferation, migration, invasion, and IGF1R expression. These findings suggest that miRNA dysregulation is involved in ccRCC progression, specifically through invasion, and that let-7c-5p downregulation contributes to the aggressiveness of small ccRCC tumors, in part, through its regulation of IGF1R.

MicroRNA let-7 and viral infections: focus on mechanisms of action

MicroRNAs (miRNAs) are fundamental post-transcriptional modulators of several critical cellular processes, a number of which are involved in host defense mechanisms. In particular, miRNA let-7 functions as an essential regulator of the function and differentiation of both innate and adaptive immune cells. Let-7 is involved in several human diseases, including cancer and viral infections. Several viral infections have found ways to dysregulate the expression of miRNAs. Extracellular vesicles (EV) are membrane-bound lipid structures released from many types of human cells that can transport proteins, lipids, mRNAs, and miRNAs, including let-7. After their release, EVs are taken up by the recipient cells and their contents released into the cytoplasm. Let-7-loaded EVs have been suggested to affect cellular pathways and biological targets in the recipient cells, and can modulate viral replication, the host antiviral response, and the action of cancer-related viruses. In the present review, we summarize the available knowledge concerning the expression of let-7 family members, functions, target genes, and mechanistic involvement in viral pathogenesis and host defense. This may provide insight into the development of new therapeutic strategies to manage viral infections.

SYNCRIP Modulates the Epithelial-Mesenchymal Transition in Hepatocytes and HCC Cells

Heterogeneous nuclear ribonucleoproteins (hnRNPs) control gene expression by acting at multiple levels and are often deregulated in epithelial tumors; however, their roles in the fine regulation of cellular reprogramming, specifically in epithelial–mesenchymal transition (EMT), remain largely unknown. Here, we focused on the hnRNP-Q (also known as SYNCRIP), showing by molecular analysis that in hepatocytes it acts as a “mesenchymal” gene, being induced by TGFβ and modulating the EMT. SYNCRIP silencing limits the induction of the mesenchymal program and maintains the epithelial phenotype. Notably, in HCC invasive cells, SYNCRIP knockdown induces a mesenchymal–epithelial transition (MET), negatively regulating their mesenchymal phenotype and significantly impairing their migratory capacity. In exploring possible molecular mechanisms underlying these observations, we identified a set of miRNAs (i.e., miR-181-a1-3p, miR-181-b1-3p, miR-122-5p, miR-200a-5p, and miR-let7g-5p), previously shown to exert pro- or anti-EMT activities, significantly impacted by SYNCRIP interference during EMT/MET dynamics and gathered insights, suggesting the possible involvement of this RNA binding protein in their transcriptional regulation.

The Roles of the Let-7 Family of MicroRNAs in the Regulation of Cancer Stemness

Cancer has long been viewed as a disease of normal development gone awry. Cancer stem-like cells (CSCs), also termed as tumor-initiating cells (TICs), are increasingly recognized as a critical tumor cell population that drives not only tumorigenesis but also cancer progression, treatment resistance and metastatic relapse. The let-7 family of microRNAs (miRNAs), first identified in C. elegans but functionally conserved from worms to human, constitutes an important class of regulators for diverse cellular functions ranging from cell proliferation, differentiation and pluripotency to cancer development and progression. Here, we review the current state of knowledge regarding the roles of let-7 miRNAs in regulating cancer stemness. We outline several key RNA-binding proteins, long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) involved in the regulation of let-7 biogenesis, maturation and function. We then highlight key gene targets and signaling pathways that are regulated or mutually regulated by the let-7 family of miRNAs to modulate CSC characteristics in various types of cancer. We also summarize the existing evidence indicating distinct metabolic pathways regulated by the let-7 miRNAs to impact CSC self-renewal, differentiation and treatment resistance. Lastly, we review current preclinical studies and discuss the clinical implications for developing let-7-based replacement strategies as potential cancer therapeutics that can be delivered through different platforms to target CSCs and reduce/overcome treatment resistance when applied alone or in combination with current chemo/radiation or molecularly targeted therapies. By specifically targeting CSCs, these strategies have the potential to significantly improve the efficacy of cancer therapies.

Long non-coding RNA NEAT1 facilitates the growth, migration, and invasion of ovarian cancer cells via the let-7 g/MEST/ATGL axis

Background/Aim

Growing evidence indicates a significant role of long non-coding RNA (lncRNA) nuclear-enriched abundant transcript 1 (NEAT1) in ovarian cancer, a frequently occurring malignant tumor in women; however, the possible effects of an interplay of NEAT1 with microRNA (miRNA or miR) let-7 g in ovarian cancer are not known. The current study aimed to investigate the role of the NEAT1/let-7 g axis in the growth, migration, and invasion of ovarian cancer cells and explore underlying mechanisms.

Methods

NEAT1 expression levels were examined in clinical tissue samples and cell lines. The relationships between NEAT1, let-7 g, and MEST were then analyzed. Gain- or loss-of-function approaches were used to manipulate NEAT1 and let-7 g. The effects of NEAT1 on cell proliferation, migration, invasion, and apoptosis were evaluated. Mouse xenograft models of ovarian cancer cells were established to verify the function of NEAT1 in vivo.

Results

NEAT1 expression was elevated while let-7 g was decreased in ovarian cancer clinical tissue samples and cell lines. A negative correlation existed between NEAT1 and let-7 g, whereby NEAT1 competitively bound to let-7 g and consequently down-regulate let-7 g expression. By this mechanism, the growth, migration, and invasion of ovarian cancer cells were stimulated. In addition, let-7 g targeted mesoderm specific transcript (MEST) and inhibited its expression, leading to promotion of adipose triglyceride lipase (ATGL) expression and inhibition of ovarian cancer cell growth, migration, and invasion. However, the effect of let-7 g was abolished by overexpression of MEST. Furthermore, silencing of NEAT1 decreased the xenograft tumor growth by decreasing MEST while up-regulating let-7 g and ATGL.

Conclusions

Cumulatively, the findings demonstrated that NEAT1 could promote malignant phenotypes of ovarian cancer cells by regulating the let-7 g/MEST/ATGL signaling axis. Therefore, NEAT1 can be regarded as an important molecular target and biomarker for ovarian cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02018-3.

Identification of miRNAs as diagnostic and prognostic markers in hepatocellular carcinoma

The development of high-throughput technologies has yielded a large amount of data from molecular and epigenetic analysis that could be useful for identifying novel biomarkers of cancers. We analyzed Gene Expression Omnibus (GEO) DataSet micro–ribonucleic acid (miRNA) profiling datasets to identify miRNAs that could have value as diagnostic and prognostic biomarkers in hepatocellular carcinoma (HCC). We adopted several computing methods to identify the functional roles of these miRNAs. Ultimately, via integrated analysis of three GEO DataSets, three differential miRNAs were identified as valuable markers in HCC. Combining the results of receiver operating characteristic (ROC) analyses and Kaplan–Meier Plotter (KM) survival analyses, we identified hsa-let-7e as a novel potential biomarker for HCC diagnosis and prognosis. Then, we found via quantitative reverse-transcription polymerase chain reaction (RT-qPCR) that let-7e was upregulated in HCC tissues and that such upregulation was significantly associated with poor prognosis in HCC. The results of functional analysis indicated that upregulated let-7e promoted tumor cell growth and proliferation. Additionally, via mechanistic analysis, we found that let-7e could regulate mitochondrial apoptosis and autophagy to adjust and control cancer cell proliferation. Therefore, the integrated results of our bioinformatics analyses of both clinical and experimental data showed that let-7e was a novel biomarker for HCC diagnosis and prognosis and might be a new treatment target.

MicroRNAs Modulate Drug Resistance-Related Mechanisms in Hepatocellular Carcinoma

Primary liver cancer [hepatocellular carcinoma (HCC)] is one of the most common malignant tumors worldwide, causing serious health threats because of its high morbidity and mortality, rapid growth, and strong invasiveness. Patients with HCC frequently develop resistance to the current chemotherapeutic drugs, and this is largely attributed to the high-level heterogeneity of the tumor tissue. MicroRNAs (miRNAs) are a group of master regulators for multiple physiological and pathological processes and play important roles in the tumorigenesis. More recent studies have indicated that miRNAs also play a non-negligible role in the development of drug resistance in liver cancer. In this review, we summarize the data from the latest studies on the mechanisms of drug resistance in liver cancer, including autophagy, membrane transporters, epithelial-mesenchymal transitions (EMTs), tumor microenvironment, and genes and proteins that are associated with apoptosis. The data herein will provide valuable information for the development of novel approaches to tackle drug resistance in the management of liver cancer.

SUMOylation modulates the LIN28A-let-7 signaling pathway in response to cellular stresses in cancer cells

LIN28A is a conserved RNA-binding protein that inhibits the biogenesis of let-7 microRNAs, thus promoting cancer progression. However, mechanisms underlying the activation of the LIN28A-let-7 signaling pathway remain poorly understood. Here, we show that LIN28A is SUMOylated in vivo and in vitro at K15, which is increased by hypoxia but reduced by chemotherapy drugs such as Cisplatin and Paclitaxel. SUMOylation of LIN28A aggravates its inhibition of let-7 maturation, resulting in a stark reduction in let-7, which promotes cancer cell proliferation, migration, invasion, and tumor growth in vivo. Mechanistically, SUMOylation of LIN28A increases its binding affinity with the precursor let-7 (pre-let-7), which subsequently enhances LIN28A-mediated recruitment of terminal uridylyltransferase TUT4 and simultaneously blocks DICER processing of pre-let-7, thereby reducing mature let-7 production. These effects are abolished in SUMOylation-deficient mutant LIN28A-K15R. In summary, these findings shed light on a novel mechanism by which SUMOylation could regulate the LIN28A-let-7 pathway in response to cellular stress in cancer cells.

High Mobility Group A (HMGA): Chromatin Nodes Controlled by a Knotty miRNA Network

High mobility group A (HMGA) proteins are oncofoetal chromatin architectural factors that are widely involved in regulating gene expression. These proteins are unique, because they are highly expressed in embryonic and cancer cells, where they play a relevant role in cell proliferation, stemness, and the acquisition of aggressive tumour traits, i.e., motility, invasiveness, and metastatic properties. The HMGA protein expression levels and activities are controlled by a connected set of events at the transcriptional, post-transcriptional, and post-translational levels. In fact, microRNA (miRNA)-mediated RNA stability is the most-studied mechanism of HMGA protein expression modulation. In this review, we contribute to a comprehensive overview of HMGA-targeting miRNAs; we provide detailed information regarding HMGA gene structural organization and a comprehensive evaluation and description of HMGA-targeting miRNAs, while focusing on those that are widely involved in HMGA regulation; and, we aim to offer insights into HMGA-miRNA mutual cross-talk from a functional and cancer-related perspective, highlighting possible clinical implications.

miR-30a-3p inhibits the proliferation of liver cancer cells by targeting DNMT3a through the PI3K/AKT signaling pathway

MicroRNAs (miRNAs or miRs) are crucial for normal development and maintenance of homeostasis. Dysregulated miRNA expression contributes to numerous pathological conditions, including cancer tumorigenesis. However, a limited number of studies have examined the regulatory effects of miR-30a-3p in tumorigenesis. Therefore, the present study investigated the mechanistic process of tumorigenesis in liver cancer. The results revealed a high expression of DNA methyltransferase 3a (DNMT3a) and a low expression of miR-30a-3p in HepG2 cells compared with that in the L02 cell line. A luciferase reporter assay demonstrated that DNMT3a is a direct target of miR-30a-3p. In addition, DNMT3a overexpression significantly enhanced cell proliferation, which was reversed by a miR-30a-3p mimic. Similarly, the miR-30a-3p mimic blocked DNMT3a-triggered cell cycle processes and apoptosis by attenuating active p-AKT and p-PI3K in HepG2 cells. In summary, the results of the present study demonstrate that miR-30a-3p is essential for cell proliferation regulation via its association with AKT/PI3K signaling in liver cancer. These results provide insight into the molecular mechanism by which miR-30a-3p inhibits liver cancer cell proliferation and provides a foundation for its clinical development and application.

Let-7 as biomarker, prognostic indicator, and therapy for precision medicine in cancer

Abnormal regulation and expression of microRNAs (miRNAs) has been documented in various diseases including cancer. The miRNA let-7 (MIRLET7) family controls developmental timing and differentiation. Let-7 loss contributes to carcinogenesis via an increase in its target oncogenes and stemness factors. Let-7 targets include genes regulating the cell cycle, cell signaling, and maintenance of differentiation. It is categorized as a tumor suppressor because it reduces cancer aggressiveness, chemoresistance, and radioresistance. However, in rare situations let-7 acts as an oncogene, increasing cancer migration, invasion, chemoresistance, and expression of genes associated with progression and metastasis. Here, we review let-7 function as tumor suppressor and oncogene, considering let-7 as a potential diagnostic and prognostic marker, and a therapeutic target for cancer treatment. We explain the complex regulation and function of different let-7 family members, pointing to abnormal processes involved in carcinogenesis. Let-7 is a promising option to complement conventional cancer therapy, but requires a tumor specific delivery method to avoid toxicity. While let-7 therapy is not yet established, we make the case that assessing its tumor presence is crucial when choosing therapy. Clinical data demonstrate that let-7 can be used as a biomarker for rational precision medicine decisions, resulting in improved patient survival.

Upregulation of Insulin-Like Growth Factor-1 Receptor (IGF-1R) Reverses the Inhibitory Effect of Let-7g-5p on Migration and Invasion of Nasopharyngeal Carcinoma

Background

Let-7 microRNAs (miRNAs) have the effects of inhibiting tumor growth and metastasis, however, the research in nasopharyngeal carcinoma (NPC) is limited. This study focused on the effects of Let-7 on NPC migration and invasion and the mechanism of action.

Material/Methods

Plasmid transfection was used to upregulate the expression levels of Let-7g-5p and insulin-like growth factor-1 receptor (IGF-1R). Cell counting kit-8 (CCK-8) assay was applied to test the cell viability. Scratch assay and Transwell assay were performed to detect the migration and invasion abilities. Bioinformatics prediction and luciferase reporter assay were used to determine and verify the downstream target genes for Let-7g-5p. Protein and mRNA were detected by western blot and real-time quantitative polymerase chain reaction (RT-qPCR), respectively.

Results

Let-7g-5p was under-expressed in human NPC cells. Overexpression of Let-7g-5p could inhibit cell viability and inhibit the migration and invasion of SUNE1 cells. The dual-luciferase reporter assay showed that IGF-1R was a direct target gene of Let-7g-5p, which was directly regulated IGF-1R expression by 3′UTR. Let-7g-5p overexpression could inhibit the expression of IGF-1R gene, and upregulation of IGF-1R gene expression reversed the inhibitory effect of Let-7g-5p on cell viability and epithelial-mesenchymal transition processes.

Conclusions

Let-7g-5p is lowly expressed in NPC and it was the first to discover that IGF-1R was a target gene of let-7g-5p in NPC. Upregulation of IGF-1R reversed the inhibitory effect of Let-7g-5p on epithelial-mesenchymal transition.

From basic researches to new achievements in therapeutic strategies of KRAS-driven cancers

Among the numerous oncogenes involved in human cancers, KRAS represents the most studied and best characterized cancer-related genes. Several therapeutic strategies targeting oncogenic KRAS (KRAS onc ) signaling pathways have been suggested, including the inhibition of synthetic lethal interactions, direct inhibition of KRAS onc itself, blockade of downstream KRAS onc effectors, prevention of post-translational KRAS onc modifications, inhibition of the induced stem cell-like program, targeting of metabolic peculiarities, stimulation of the immune system, inhibition of inflammation, blockade of upstream signaling pathways, targeted RNA replacement, and oncogene-induced senescence. Despite intensive and continuous efforts, KRAS onc remains an elusive target for cancer therapy. To highlight the progress to date, this review covers a collection of studies on therapeutic strategies for KRAS published from 1995 to date. An overview of the path of progress from earlier to more recent insights highlight novel opportunities for clinical development towards KRASonc-signaling targeted therapeutics.

Functional Effects of let-7g Expression in Colon Cancer Metastasis

MicroRNA regulation is crucial for gene expression and cell functions. It has been linked to tumorigenesis, development and metastasis in colorectal cancer (CRC). Recently, the let-7 family has been identified as a tumor suppressor in different types of cancers. However, the function of the let-7 family in CRC metastasis has not been fully investigated. Here, we focused on analyzing the role of let-7g in CRC. The Cancer Genome Atlas (TCGA) genomic datasets of CRC and detailed data from a Taiwanese CRC cohort were applied to study the expression pattern of let-7g. In addition, in vitro as well as in vivo studies have been performed to uncover the effects of let-7g on CRC. We found that the expression of let-7g was significantly lower in CRC specimens. Our results further supported the inhibitory effects of let-7g on CRC cell migration, invasion and extracellular calcium influx through store-operated calcium channels. We report a critical role for let-7g in the pathogenesis of CRC and suggest let-7g as a potential therapeutic target for CRC treatment.

Mechanistic regulation of epithelial-to-mesenchymal transition through RAS signaling pathway and therapeutic implications in human cancer

RAS effector signaling instead of being simple, unidirectional and linear cascade, is actually recognized as highly complex and dynamic signaling network. RAF-MEK-ERK cascade, being at the center of complex signaling network, links to multiple scaffold proteins through feed forward and feedback mechanisms and dynamically regulate tumor initiation and progression. Three isoforms of Ras harbor mutations in a cell and tissue specific manner. Besides mutations, their epigenetic silencing also attributes them to exhibit oncogenic activities. Recent evidences support the functions of RAS oncoproteins in the acquisition of tumor cells with Epithelial-to-mesenchymal transition (EMT) features/ epithelial plasticity, enhanced metastatic potential and poor patient survival. Google Scholar electronic databases and PubMed were searched for original papers and reviews available till date to collect information on stimulation of EMT core inducers in a Ras driven cancer and their regulation in metastatic spread. Improved understanding of the mechanistic basis of regulatory interactions of microRNAs (miRs) and EMT by reprogramming the expression of targets in Ras activated cancer, may help in designing effective anticancer therapies. Apparent lack of adverse events associated with the delivery of miRs and tissue response make 'drug target miRNA' an ideal therapeutic tool to achieve progression free clinical response.

The Molecular Basis and Therapeutic Potential of Let-7 MicroRNAs against Colorectal Cancer

Although a number of studies have revealed the underlying mechanisms which regulate the development of colorectal cancer (CRC), we have not completely overcome this disease yet. Accumulating evidence has shown that the posttranscriptional regulation by the noncoding RNAs such as microRNAs plays an important role in the development or progression of CRC. Among a number of microRNAs, the let-7 microRNA family that was first discovered in C. elegans and conserved from worms to humans has been linked with the development of many types of cancers including CRC. The expression level of let-7 microRNAs is temporally low during the normal developmental processes, while elevated in the differentiated tissues. The let-7 microRNAs regulate the cell proliferation, cell cycle, apoptosis, metabolism, and stemness. In CRC, expressions of let-7 microRNAs have been reported to be reduced, and so let-7 microRNAs are considered to be a tumor suppressor. In this review, we discuss the mechanisms regulating the let-7 microRNA expression and the downstream targets of let-7 in the context of intestinal tumorigenesis. The application of let-7 mimics is also highlighted as a novel therapeutic agent.

Epigenetic Contribution of High-Mobility Group A Proteins to Stem Cell Properties

High-mobility group A (HMGA) proteins have been examined to understand their participation as structural epigenetic chromatin factors that confer stem-like properties to embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), and cancer stem cells (CSCs). The function of HMGA was evaluated in conjunction with that of other epigenetic factors such as histones and microRNAs (miRs), taking into consideration the posttranscriptional modifications (PTMs) of histones (acetylation and methylation) and DNA methylation. HMGA proteins were coordinated or associated with histone and DNA modification and the expression of the factors related to pluripotency. CSCs showed remarkable differences compared with ESCs and iPSCs.

miR-302a-5p/367-3p-HMGA2 axis regulates malignant processes during endometrial cancer development

BACKGROUND

Metastasis is one of the main reasons for treatment failure in endometrial cancer. Notably, high mobility group AT-hook 2 (HMGA2) has been recognized as a driving factor of tumour metastasis. microRNAs (miRNAs) are powerful posttranscriptional regulators of HMGA2.

METHODS

The binding sites of miR-302a-5p and miR-367-3p on HMGA2 mRNA were identified using bioinformatics prediction software and were validated via luciferase assay. The expression levels of miR-302a-5p and miR-367-3p were detected using quantitative real-time PCR and in situ hybridization. Western blotting and immunohistochemistry were used to detect the levels of HMGA2 and epithelial-mesenchymal transition pathway-related proteins. Co-immunoprecipitation was used to detect protein interactions. The roles of miR-302a-5p and miR-367-3p in the regulation of HMGA2 during the progression of endometrial cancer were investigated using both in vitro and in vivo assays.

RESULTS

In the present study, high HMGA2 expression was correlated with poor clinical outcomes in endometrial cancer. The binding sites of miRNAs on HMGA2 mRNA were identified using bioinformatics prediction software and were validated via luciferase assay. In the endometrial cancer cell lines Ishikawa and HEC-1A, the overexpression of miR-302a-5p/367-3p significantly inhibited the expression of HMGA2 mRNA. In endometrial cancer tissues, we showed that miR-302a-5p and miR-367-3p were significantly downregulated and thus inversely correlated with HMGA2. The miR-302a-5p and miR-367-3p expression levels were closely correlated with FIGO stage and lymph node metastasis. High expression of miR-302a-5p/367-3p was correlated with high survival rates in endometrial cancer. In addition, miR-302a-5p/367-3p suppressed the malignant behaviour of endometrial carcinoma cells via the inhibition of HMGA2 expression.

CONCLUSION

Our findings indicate that miR-302a-5p/367-3p-mediated expression of HMGA2 regulates the malignant behaviour of endometrial carcinoma cells, which suggests that the miR-302a-5p/367-3p-HMGA2 axis may be a predictive biomarker of endometrial cancer metastasis and patient survival and a potential therapeutic target in metastatic endometrial cancer.

MicroRNAs and cancer: Key paradigms in molecular therapy

MicroRNAs (miRNAs) are a type of small non-coding RNA molecule that performs an important role in post-transcriptional gene regulation. Since miRNAs were first identified in 1993, a number of studies have demonstrated that they act as tumor suppressors or oncogenes in human cancer, including colorectal, lung, brain, breast and liver cancer, and leukemia. Large high-throughput studies have previously revealed that miRNA profiling is critical for the diagnosis and prognosis of patients with cancer, while certain miRNAs possess the potential to be used as diagnostic and prognostic biomarkers or therapeutic targets in cancer. The present study reviews the studies and examines the roles of miRNAs in cancer diagnosis, prognosis and treatment, and discusses the potential therapeutic modality of exploiting miRNAs.

Lin28B facilitates the progression and metastasis of pancreatic ductal adenocarcinoma

Lin28B, a Lin28 homologue, represses the biogenesis of let-7 microRNAs (miRNAs), has a role in tumorigenesis, and is considered a potential therapeutic target for various human malignancies. However, the associations between Lin28B and the clinical features and outcomes of patients with pancreatic ductal adenocarcinoma (PDAC) remain unclear. In this study, we explored the clinical significance of Lin28B in PDAC and its association with metastasis by examining tissues from patients with PDAC and elucidated the molecular mechanisms using PDAC cell lines. In patients, high Lin28B expression was significantly correlated with high levels of lymphatic metastasis, distant metastasis and a poor prognosis. Furthermore, the multivariate analysis identified Lin28B expression as an independent prognostic factor in patients. In cell lines, stable silencing of Lin28B inhibited cell proliferation, cell cycle transition, migration and the epithelial-mesenchymal transition (EMT). It also increased the expression of the c-MYC, HMGA2 and KRAS genes, which are targeted by the cancer-suppressor miRNA let-7. Lin28B overexpression in the PDAC cell lines had the opposite effect. In human PDAC samples, high Lin28B expression was associated with decreased let-7 expression and increased c-MYC, HMGA2 and KRAS expression. Thus, Lin28B is a novel marker for predicting the prognosis of patients with PDAC and might be a potential therapeutic target for PDAC.

Recent progress on the effects of microRNAs and natural products on tumor epithelial-mesenchymal transition

Epithelial–mesenchymal transition (EMT) is a biological process of phenotypic transition of epithelial cells that can promote physiological development as well as tissue healing and repair. In recent years, cancer researchers have noted that EMT is closely related to the occurrence and development of tumors. When tumor cells undergo EMT, they can develop enhanced migration and local tissue invasion abilities, which can lead to metastatic growth. Nevertheless, two researches in NATURE deny its necessity in specific tumors and that is discussed in this review. The degree of EMT and the detection of EMT-associated marker molecules can also be used to judge the risk of metastasis and to evaluate patients’ prognosis. MicroRNAs (miRNAs) are noncoding small RNAs, which can inhibit gene expression and protein translation through specific binding with the 3′ untranslated region of mRNA. In this review, we summarize the miRNAs that are reported to influence EMT through transcription factors such as ZEB, SNAIL, and TWIST, as well as some natural products that regulate EMT in tumors. Moreover, mutual inhibition occurs between some transcription factors and miRNAs, and these effects appear to occur in a complex regulatory network. Thus, understanding the role of miRNAs in EMT and tumor growth may lead to new treatments for malignancies. Natural products can also be combined with conventional chemotherapy to enhance curative effects.

Tissue MicroRNA profiles as diagnostic and prognostic biomarkers in patients with resectable pancreatic ductal adenocarcinoma and periampullary cancers

Background

The aim of this study was to validate previously described diagnostic and prognostic microRNA expression profiles in tissue samples from patients with pancreatic cancer and other periampullary cancers.

Methods

Expression of 46 selected microRNAs was studied in formalin-fixed paraffin-embedded tissue from patients with resected pancreatic ductal adenocarcinoma (n = 165), ampullary cancer (n=59), duodenal cancer (n = 6), distal common bile duct cancer (n = 21), and gastric cancer (n = 20); chronic pancreatitis (n = 39); and normal pancreas (n = 35). The microRNAs were analyzed by PCR using the Fluidigm platform.

Results

Twenty-two microRNAs were significantly differently expressed in patients with pancreatic cancer when compared to healthy controls and chronic pancreatitis patients; 17 miRNAs were upregulated (miR-21-5p, −23a-3p, −31-5p, −34c-5p, −93-3p, −135b-3p, −155-5p, −186-5p, −196b-5p, −203, −205-5p, −210, −222-3p, −451, −492, −614, and miR-622) and 5 were downregulated (miR-122-5p, −130b-3p, −216b, −217, and miR-375). MicroRNAs were grouped into diagnostic indices of varying complexity. Ten microRNAs associated with prognosis were identified (let-7 g, miR-29a-5p, −34a-5p, −125a-3p, −146a-5p, −187, −205-5p, −212-3p, −222-5p, and miR-450b-5p). Prognostic indices based on differences in expression of 2 different microRNAs were constructed for pancreatic and ampullary cancer combined and separately (30, 5, and 21 indices).

Conclusion

The study confirms that pancreatic cancer tissue has a microRNA expression profile that is different from that of other periampullary cancers, chronic pancreatitis, and normal pancreas. We identified prognostic microRNAs and microRNA indices that were associated with shorter overall survival in patients with radically resected pancreatic cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s40364-017-0087-6) contains supplementary material, which is available to authorized users.

Role of let-7 family microRNA in breast cancer

Metastasis and resistance to therapy significantly contribute to cancer-related deaths. Growing body of evidence suggest that altered expression of microRNAs (miRNAs) is one of the root cause of adverse clinical outcome. miRNAs such as let-7 are the new fine tuners of signaling cascade and cellular processes which regulates the genes in post-transcriptional manner. In this review, we described the regulation of let-7 expression and the involvement of molecular factors in this process. We discussed the mechanism by which let-7 alter the expression of genes involved in the process of tumorigenesis. Further, we listed the pathways targeted by let-7 to reduce the burden of the tumor. In addition, we described the role of let-7 in breast cancer metastasis and stemness properties. This article will provide the in-depth insight into the biology of let-7 miRNA and its role in the breast cancer progression.

Hsa-let-7g miRNA regulates the anti-tumor effects of gastric cancer cells under oxidative stress through the expression of DDR genes

Oxidative stress is linked to increased risk of gastric cancer (GC). Recent reports have found that hsa-let-7 g microRNA (miRNA) has properties of anti-tumor and resistance to damages induced by oxidized low-density lipoprotein (ox-LDL). Dysregulation of hsa-let-7 g was present in GC in vivo and in vitro under exogenous stress. However, we didn't know whether there are regulatory mechanisms of hsa-let-7 g in GC under oxidative stress. This study was aimed at investigating the effects of hsa-let-7 g microRNA (miRNA) on GC under oxidative stress. The results showed that H2O2 induced the increase of DNA damage response (DDR) genes (ATM, H2AX and Chk1) and downregulation of hsa-let-7 g in GC cells. Further study confirmed Hsa-let-7 g caused the apoptosis and loss of proliferation in GC cells exposed to H2O2 associated with repression of DDR system. Yet, we found let-7 g didn't target DDR genes (ATM, H2AX and Chk1) directly. In addition, data revealed hsa-let-7 g miRNA increased the sensitivity of GC to X-rays involving in ATM regulation as well according to application of X-rays (another DDR inducer). In conclusion, Hsa-let-7 g miRNA increased the sensitivity of GC to oxidative stress by repression activation of DDR indirectly. Let-7 g improved the effects of X-rays on GC cells involving in DDR regulation as well.

Let-7a suppresses glioma cell proliferation and invasion through TGF-β/Smad3 signaling pathway by targeting HMGA2

It has been shown that let-7a was associated with the tumorigenesis of glioma. Our study was designed to infer how let-7a targets high-mobility AT-hook 2 (HMGA2) and suppresses glioma cell proliferation, invasion, and migration. Glioma tissues from 60 glioma patients and 10 normal brain tissues were collected in this study. Real-time quantitative reverse transcription-PCR (qRT-PCR) and in situ hybridization were used to detect the expression levels of let-7a in tissues and cells. The HMGA2 and the proteins related to transforming growth factor-beta (TGF-β)/Smad3 signaling pathway were measured by immunohistochemistry and western blot. Glioma U87 cells were transfected with either let-7a mimics, HMGA2 small interfering RNA (siRNA), let-7a mimics + HMGA2, HMGA2, or scramble. A cell counting kit-8 (CCK-8) assay was used to detect and compare the difference among various transfection groups. Glioma tumor xenograft models on mice were built to evaluate the effects of let-7a and HMGA2 siRNA on glioma tumors in vivo. The expression level of let-7a significantly downregulated in glioma tissues, while the HMGA2 positive expression rate notably increased compared with those in normal brain tissues (all P < 0.05). Moreover, the expression levels of let-7a and HMGA2 were correlated with glioma grades (all P < 0.05). The proliferation of U87 cells transfected with let-7a mimics or HMGA2 siRNA was significantly inhibited in comparison to the blank control group and the apoptosis rates of U87 cells transfected with let-7a mimics or HMGA2 siRNA were significantly higher than those in the blank control group (all P < 0.05). Let-7a or HMGA2 siRNA could remarkably attenuate the invasion and migration ability of glioma cells (all P < 0.05). Apart from that, over-expressed exogenous HMGA2 could reverse the inhibition of glioma cell metastasis and proliferation induced by let-7a. As suggested by immunohistochemistry and western blot, the expression levels of TGF-β1 and p-Smad3 significantly decreased compared with the blank or scramble group (all P < 0.05). Thus, let-7a and HMGA2 siRNA could effectively suppress the growth of tumors in glioma xenograft models. Let-7a may suppress the proliferation and invasion of glioma cells through mediating TGF-β/Smad3 signaling pathway by targeting HMGA2.

Combinatorial interventions inhibit TGFβ-driven epithelial-to-mesenchymal transition and support hybrid cellular phenotypes

Epithelial-to-mesenchymal transition (EMT) is a developmental process hijacked by cancer cells to leave the primary tumor site, invade surrounding tissue and establish distant metastases. A hallmark of EMT is the loss of E-cadherin expression, and one major signal for the induction of EMT is transforming growth factor beta (TGFβ), which is dysregulated in up to 40% of hepatocellular carcinoma (HCC). We aim to identify network perturbations that suppress TGFβ-driven EMT, with the goal of suppressing invasive properties of cancer cells. We use a systems-level Boolean dynamic model of EMT to systematically screen individual and combination perturbations (inhibition or constitutive activation of up to four nodes). We use a recently developed network control approach to understand the mechanism through which the combinatorial interventions suppress EMT. We test the results of our in silico analysis using siRNA. Our model predicts that targeting key elements of feedback loops in combination with the SMAD complex is more effective than suppressing the SMAD complex alone. We demonstrate experimentally that expression of a majority of these elements is enriched in mesenchymal relative to epithelial phenotype HCC cell lines. An siRNA screen of the predicted combinations confirms that many targeting strategies suppress TGFβ-driven EMT measured by E-cadherin expression and cell migration. Our analysis reveals that some perturbations give rise to hybrid states intermediate to the epithelial and mesenchymal states. Our results indicate that EMT is driven by an interconnected signaling network and many apparently successful single interventions may lead to steady states that are in-between epithelial and mesenchymal states. As these putative hybrid or partial EMT states may retain invasive properties, our results suggest that combinatorial therapies are necessary to fully suppress invasive properties of tumor cells.

Oncogenic miR-9 is a target of erlotinib in NSCLCs

EGFR-targeted cancer therapy is a breakthrough in non-small cell carcinoma. miRNAs have been proved to play important roles in cancer. Currently, for the role of miRNAs in EGFR-targeted cancer therapy is unclear. In this study, first we found that erlotinib reduced the expression of miR-9. MiR-9 expression was increased in human lung cancer tissues compared with peripheral normal tissues, and miR-9 promoted the growth of NSCLC cells. Overexpression of miR-9 decreased the growth inhibitory effect of erlotinib. Second, miR-9 decreased FoxO1 expression by directly inhibition of its mRNA translation. Adenovirus-mediated overexpression of FoxO1 or siRNA-mediated downregulation of FoxO1 negatively regulated cell growth. And exogenous overexpression FoxO1 reduced the pro-growth effect of miR-9. Finally, we found that erlotinib upregulated FoxO1 protein expression. Moreover, overexpression of miR-9 decreased erlotinib-induced FoxO1 expression, and overexpression of FoxO1 enhanced the growth inhibitory effects of erlotinib. Additionally, we found that erlotinib downregulates miR-9 expression through suppressing the transcrption of miR-9-1 and enhanced DNA methylation maybe involved. These findings suggest that oncogenic miR-9 targeted FoxO1 to promote cell growth, and downregulation of this axis was involved in erlotinib’s growth inhibitory effects. Clarifying the regulation of miRNAs by erlotinib may indicate novel strategies for enhancing EGFR-targeted cancer therapy.

Aberrant regulation of the LIN28A/LIN28B and let-7 loop in human malignant tumors and its effects on the hallmarks of cancer

RNA binding proteins (RBPs) and microRNAs (miRNAs) are two of the most important post-transcriptional regulators of gene expression, and their aberrant expression contributes to the development of human malignancies. Let-7, one of the most well-known tumor suppressors, is frequently down-regulated in a variety of human cancers. The RBP LIN28A/LIN28B, a direct target of the let-7 family of miRNAs, is an inhibitor of let-7 biogenesis and is frequently up-regulated in cancers. Aberrant regulation of the LIN28A/LIN28B and let-7 loop in human malignant tumors is reportedly involved in cancer development, contributing to cellular proliferation, cell death resistance, angiogenesis, metastasis, metabolism reprogramming, tumor-associated inflammation, genome instability, acquiring immortality and evading immune destruction. In this review, we summarized the mechanisms of LIN28A/LIN28B and let-7 loop aberrant regulation in human cancer and discussed the roles and potential mechanisms of the LIN28A/LIN28B and let-7 loop in regulating the hallmarks of cancer. The crosstalk between LIN28A/LIN28B and let-7 loop and certain oncogenes (such as MYC, RAS, PI3K/AKT, NF-κB and β-catenin) in regulating hallmarks of cancer has also been discussed.

Long noncoding RNA CCAT1 promotes hepatocellular carcinoma progression by functioning as let-7 sponge

BACKGROUND

Long noncoding RNAs (lncRNAs) have been identified as having functional roles in cancer biology and are deregulated in many cancers. The present study aimed to determine the expression, roles and functional mechanisms of a long noncoding RNA CCAT1 in the progression of hepatocellular carcinoma (HCC).

METHODS

CCAT1 expression levels in 66 pairs of HCC tissues and pair-matched noncancerous hepatic tissues were tested by real-time PCR. The effects of CCAT1 on HCC cells proliferation and migration were assessed using in vitro cell proliferation and migration assays. A computational screen of microRNAs (miRNAs) target sites in CCAT1 was conducted to search for specific miRNAs binding to CCAT1. The specific binding between CCAT1 and miRNAs was confirmed by RNA immunoprecipitation assay combined with luciferase reporter assay.

RESULTS

CCAT1 levels are markedly increased in HCC tissues compared with pair-matched noncancerous hepatic tissues. Up-regulation of CCAT1 is correlated with tumor size, microvascular invasion, AFP and poor prognosis. CCAT1 promotes the proliferation and migration of HCC cells. CCAT1 functions as a molecular sponge for let-7, antagonizes its functions, and leads to the de-repression of its endogenous targets HMGA2 and c-Myc. The effect of CCAT1 on HCC cell proliferation and migration is dependent upon its competitively binding to let-7.

CONCLUSIONS

These data suggest that CCAT1 plays a pivotal role in HCC progression via functioning as let-7 sponge, and implicate the potential application of CCAT1 for the prognosis and treatment of HCC.

RKIP inhibits gastric cancer cell survival and invasion by regulating the expression of HMGA2 and OPN

The objective of this study was to explore the mechanism via which Raf kinase inhibitor protein (RKIP) suppresses the invasion of gastric cancer cells and promote apoptosis, with an attempt to provide evidences for the application of RKIP in treating gastric cancer. The recombinant plasmid pcDNA3.1-RKIP or RKIP-shRNA was transfected into the gastric cancer cell line SGC-7901 using liposome. Then, the messenger RNA (mRNA) and protein expressions of RKIP, HMGA2, and OPN were detected using qPCR and Western blotting. The effects of HMGA2 on the proliferation, apoptosis, and invasion of SGC-7901 cells were detected using flow cytometry and Transwell assay. To further explore the regulatory effect of PKIP on the biological activities of HMGA2, we over-expressed or knock down RKIP and HMGA2 simultaneously and detected its effects on the proliferation, apoptosis, and invasion of SGC-7901 cells. As shown by qPCR and Western blotting, after over-expression of RKIP in SGC-7901 cells, the mRNA and protein expressions of RKIP significantly increased (P < 0.01), whereas the mRNA and protein expressions of HMGA2 and OPN significantly decreased (P < 0.01). In contrast, the transfection of RKIP-shRNA in the SGC-7901 cells resulted in opposite results. After over-expression of HMGA2 in SGC-7901 cells, the protein expression of HMGA2 significantly increased (P < 0.01); however, it significantly decreased after the transfection of HMGA2-shRNA (P < 0.01). As shown by Transwell assay and flow cytometry, After the over-expression of HMGA2 in SGC-7901 cells, the (G2 + S) phase fraction significantly increased (P < 0.01); also, the percentage of the apoptotic cells significantly declined (P < 0.05) and the number of invasive cells significantly increased (P < 0.05). However, the interference of the expression of HMGA2 resulted in opposite results. The simultaneous over-expression of RKIP and HMGA2 in SGC-7901 cells or the simultaneous interference of RKIP and HMGA2 showed no significant difference with the control group in terms of (G2 + S) phase fraction, percentage of apoptotic cells, and number of invasive cells (P > 0.05). In conclusion, RKIP can inhibit the survival and invasion of gastric cancer cells and promote apoptosis, possibly by regulating the expression of HMGA2 or OPN.