Metformin-Derived Growth Inhibition in Renal Cell Carcinoma Depends on miR-21-Mediated PTEN Expression

Decoding PTEN regulation in clear cell renal cell carcinoma: Pathway for biomarker discovery and therapeutic insights

Renal cell carcinoma is the most common adult renal solid tumor and the deadliest urological cancer, with clear cell renal cell carcinoma (ccRCC) being the predominant subtype. The PI3K/AKT signaling pathway assumes a central role in ccRCC tumorigenesis, wherein its abnormal activation confers a highly aggressive phenotype, leading to swift resistance against current therapies and distant metastasis. Thus, treatment resistance and disease progression remain a persistent clinical challenge in managing ccRCC effectively. PTEN, an antagonist of the PI3K/AKT signaling axis, emerges as a crucial factor in tumor progression, often experiencing loss or inactivation in ccRCC, thereby contributing to elevated mortality rates in patients. Therefore, understanding the molecular mechanisms underlying PTEN suppression in ccRCC tumors holds promise for the discovery of biomarkers and therapeutic targets, ultimately enhancing patient monitoring and treatment outcomes. The present review aims to summarize these mechanisms, emphasizing their potential prognostic, predictive, and therapeutic value in managing ccRCC.

MicroRNA-21 in urologic cancers: from molecular mechanisms to clinical implications

The three most common kinds of urologic malignancies are prostate, bladder, and kidney cancer, which typically cause substantial morbidity and mortality. Early detection and effective treatment are essential due to their high fatality rates. As a result, there is an urgent need for innovative research to improve the clinical management of patients with urologic cancers. A type of small noncoding RNAs of 22 nucleotides, microRNAs (miRNAs) are well-known for their important roles in a variety of developmental processes. Among these, microRNA-21 (miR-21) stands out as a commonly studied miRNA with implications in tumorigenesis and cancer development, particularly in urological tumors. Recent research has shed light on the dysregulation of miR-21 in urological tumors, offering insights into its potential as a prognostic, diagnostic, and therapeutic tool. This review delves into the pathogenesis of miR-21 in prostate, bladder, and renal cancers, its utility as a cancer biomarker, and the therapeutic possibilities of targeting miR-21.

Renal functional outcomes after nephrectomy in patients with localized renal cell carcinoma and diabetes mellitus: a systematic review and meta-analysis

INTRODUCTION AND OBJECTIVE

Diabetes mellitus (DM), one of the most common comorbidities in patients with renal cell carcinoma (RCC), was proven to be an important prognostic factor of overall survival for these patients. Regarding the influence on renal function after nephrectomy, evidence is still scant. This systematic review and meta-analysis was conducted to provide a more reliable analysis of the association between DM and long-term renal functional outcomes after nephrectomy.

METHODS

The PubMed, Web of Science, Embase and Cochrane Library (CENTRAL) databases were searched for eligible studies from inception to January 2023. Hazard ratios (HRs) with 95% confidence intervals (CIs) were extracted to evaluate the association between DM and renal functional outcomes using a random effects model. Stata 17.0 software was used for statistical analysis.

RESULTS

The meta-analysis included thirteen studies consisting of 8562 RCC patients who underwent nephrectomy. Preoperative comorbidity of DM was significantly associated with poor renal functional outcomes (HR = 1.91, 95% CI 1.48-2.48, p < 0.0001), regardless of ethnicity, follow-up time, body mass index (BMI) and age. However, in the radical nephrectomy subgroup, DM was not significantly associated with renal function decline (HR = 1.91, 95% CI 0.93-3.90, p = 0.0781).

CONCLUSIONS

The aggregate evidence indicated that preexisting DM may be associated with poor renal functional outcomes in patients with RCC after nephrectomy, especially in patients receiving partial nephrectomy. Urologists should focus more on the glycemic management of these patients after nephrectomy. More high-quality studies are needed to explore the influence of DM on renal function outcomes in postoperative patients.

Mechanisms of Regulation of the Expression of miRNAs and lncRNAs by Metformin in Ovarian Cancer

Ovarian cancer (OC) is one of the most lethal gynecological malignancies. The use of biological compounds such as non-coding RNAs (ncRNAs) is being considered as a therapeutic option to improve or complement current treatments since the deregulation of ncRNAs has been implicated in the pathogenesis and progression of OC. Old drugs with antitumoral properties have also been studied in the context of cancer, although their antitumor mechanisms are not fully clear. For instance, the antidiabetic drug metformin has shown pleiotropic effects in several in vitro models of cancer, including OC. Interestingly, metformin has been reported to regulate ncRNAs, which could explain its diverse effects on tumor cells. In this review, we discuss the mechanism of epigenetic regulation described for metformin, with a focus on the evidence of metformin-dependent microRNA (miRNAs) and long non-coding RNA (lncRNAs) regulation in OC.

Critical Evaluation of a microRNA-Based Risk Classifier Predicting Cancer-Specific Survival in Renal Cell Carcinoma with Tumor Thrombus of the Inferior Vena Cava

(1) Background: Clear cell renal cell carcinoma extending into the inferior vena cava (ccRCCIVC) represents a clinical high-risk setting. However, there is substantial heterogeneity within this patient subgroup regarding survival outcomes. Previously, members of our group developed a microRNA(miR)-based risk classifier—containing miR-21-5p, miR-126-3p and miR-221-3p expression—which significantly predicted the cancer-specific survival (CSS) of ccRCCIVC patients. (2) Methods: Examining a single-center cohort of tumor tissue from n = 56 patients with ccRCCIVC, we measured the expression levels of miR-21, miR-126, and miR-221 using qRT-PCR. The prognostic impact of clinicopathological parameters and miR expression were investigated via single-variable and multivariable Cox regression. Referring to the previously established risk classifier, we performed Kaplan–Meier analyses for single miR expression levels and the combined risk classifier. Cut-off values and weights within the risk classifier were taken from the previous study. (3) Results: miR-21 and miR-126 expression were significantly associated with lymphonodal status at the time of surgery, the development of metastasis during follow-up, and cancer-related death. In Kaplan–Meier analyses, miR-21 and miR-126 significantly impacted CSS in our cohort. Moreover, applying the miR-based risk classifier significantly stratified ccRCCIVC according to CSS. (4) Conclusions: In our retrospective analysis, we successfully validated the miR-based risk classifier within an independent ccRCCIVC cohort.

Action Mechanism of Metformin and Its Application in Hematological Malignancy Treatments: A Review

Hematologic malignancies (HMs) mainly include acute and chronic leukemia, lymphoma, myeloma and other heterogeneous tumors that seriously threaten human life and health. The common effective treatments are radiotherapy, chemotherapy and hematopoietic stem cell transplantation (HSCT), which have limited options and are prone to tumor recurrence and (or) drug resistance. Metformin is the first-line drug for the treatment of type 2 diabetes (T2DM). Recently, studies identified the potential anti-cancer ability of metformin in both T2DM patients and patients that are non-diabetic. The latest epidemiological and preclinical studies suggested a potential benefit of metformin in the prevention and treatment of patients with HM. The mechanism may involve the activation of the adenosine monophosphate-activated protein kinase (AMPK) signaling pathway by metformin as well as other AMPK-independent pathways to exert anti-cancer properties. In addition, combining current conventional anti-cancer drugs with metformin may improve the efficacy and reduce adverse drug reactions. Therefore, metformin can also be used as an adjuvant therapeutic agent for HM. This paper highlights the anti-hyperglycemic effects and potential anti-cancer effects of metformin, and also compiles the in vitro and clinical trials of metformin as an anti-cancer and chemosensitizing agent for the treatment of HM. The need for future research on the use of metformin in the treatment of HM is indicated.

Synergic Effect of Metformin and Everolimus on Mitochondrial Dynamics of Renal Cell Carcinoma

Renal cell carcinoma (RCC) frequently recurs or metastasizes after surgical resection. Everolimus, an mTOR inhibitor, is used as a second-line treatment, but the response of RCC to everolimus is insufficient. Metformin is an antidiabetic drug; recent reports have indicated its anti-cancer effects in various cancers, and it is known to have synergistic effects with other drugs. We investigated the possibility of coadministering everolimus and metformin as an effective treatment for RCC. RCC cells treated with a combination of the two drugs showed significantly inhibited cell viability, cell migration, and invasion, and increased apoptosis compared to those treated with each drug alone. An anti-cancer synergistic effect was also confirmed in the xenograft model. Transcriptome analysis for identifying the underlying mechanism of the combined treatment showed the downregulation of mitochondrial fusion genes and upregulation of mitochondrial fission genes by the combination treatment. Changes in mitochondrial dynamics following the combination treatment were observed using LysoTracker, LysoSensor, and JC-1 staining. In conclusion, the combination of everolimus and metformin inhibited RCC growth by disrupting mitochondrial dynamics. Therefore, we suggest that a treatment combining metformin and everolimus disrupts mitochondrial dynamics in RCC, and may be a novel strategy for RCC treatment.

Advances in exosome biomarkers for cervical cancer

Cervical cancer (CC) ranks as the fourth most frequently diagnosed malignancy in females worldwide. Exosomes are a subclass of extracellular vesicles released by nearly all types of cells that act as cargo transport vehicles, carrying proteins, and genetic material (such as miRNAs, long noncoding RNAs, and mRNAs) derived from their parent cells may affect receiving cells and thus have emerged as key players in several biological processes, including inflammatory pathways. In this review, we concentrated on the findings of exosome investigations in CC, particularly their components. They direct the actions of CC cells by inducing surface molecules associated with various biological pathways. We summarized the current knowledge of exosomal RNAs and proteins from CC cells and discussed the feasibility of exosomes as potential biomarkers for CC. We suggest that cancer-derived exosomes promote metastasis in CC by supporting EMT, controlling the proliferation, invasion, or migration of cancer cells, as well as influencing immune escape and aiding angiogenesis. Overall, cancer-derived exosomes are critical in the progression of CC, and further studies are necessary to advance our understanding of the clinical value of exosomes in CC.

MicroRNAs' role in the environment-related non-communicable diseases and link to multidrug resistance, regulation, or alteration

The discovery of microRNAs (miRNAs) 20 years ago has advocated a new era of "small molecular genetics." About 2000 miRNAs are present that regulate one third of the genome. MiRNA dysregulated expression arising as a response to our environment insult or stress or changes may contribute to several diseases, namely non-communicable diseases, including tumor growth. Their presence in body fluids, reflecting level alteration in various cancers, merit circulating miRNAs as the "next-generation biomarkers" for early-stage tumor diagnosis and/or prognosis. Herein, we performed a comprehensive literature search focusing on the origin, biosynthesis, and role of miRNAs and summarized the foremost studies centering on miR value as non-invasive biomarkers in different environment-related non-communicable diseases, including various cancer types. Moreover, during chemotherapy, many miRNAs were linked to multidrug resistance, via modulating numerous, environment triggered or not, biological processes and/or pathways that will be highlighted as well.

How metformin affects various malignancies by means of microRNAs: a brief review

Metformin known as the first-line orally prescribed drug for lowering blood glucose in type II diabetes (T2DM) has recently found various therapeutic applications including in cancer. Metformin has been studied for its influences in prevention and treatment of cancer through multiple mechanisms such as microRNA (miR) regulation. Alteration in the expression of miRs by metformin may play an important role in the treatment of various cancers. MiRs are single-stranded RNAs that are involved in gene regulation. By binding to the 3'UTR of target mRNAs, miRs influence protein levels. Irregularities in the expression of miRs that control the expression of oncogenes and tumor suppressor genes are associated with the onset and progression of cancer. Metformin may possess an effect on tumor prevention and progression by modifying miR expression and downstream pathways. Here, we summarize the effect of metformin on different types of cancer by regulating the expression of various miRs and the associated downstream molecules.

Metformin mediated microRNA-7 upregulation inhibits growth, migration, and invasion of non-small cell lung cancer A549 cells

Metformin, a medication widely used in the treatment of type 2 diabetes mellitus, has a possible antitumor effect in type 2 diabetes mellitus patients. MicroRNA-7 is a significant microRNA in non-small cell lung cancer. Metformin has an inhibitory effect on lung cancer and regulates the expression of certain microRNAs, but there is no report connecting metformin with microRNA-7 in lung cancer. Thus, we used qPCR to measure microRNA-7 expression in A549 non-small cell lung cancer cells treated with metformin. We used CCK8, cell scratch, and Transwell assays to test the growth, migration, and invasion of A549 cells. Western blotting was used to measure the expression level of relevant proteins in A549 cells. We found that microRNA-7 was dramatically upregulated by metformin via AMPK in a dose- and time-dependent manner. Both metformin and microRNA-7 mimic reduced A549 cell growth, migration, and invasion. Metformin downregulated the levels of p-NF-κB p65, p-Erk1/2, p-AKT, and p-mTOR proteins. The treatment with the microRNA-7 mimic had the same result. The decrease of these proteins caused the inhibition of A549 cell growth, migration, and invasion. Our discovery revealed that metformin, via increasing the expression of microRNA-7 mediated by AMPK, regulates the AKT/mTOR, MAPK/Erk, and NF-κB signaling pathways, thereby suppressing A549 cell growth, migration, and invasion.

Identification of a novel immune-related microRNA prognostic model in clear cell renal cell carcinoma

Background

Clear cell renal cell carcinoma (ccRCC) is a type of kidney cancer, and one of the most common malignant tumors. Many studies have shown that certain microRNAs (miRNAs) play an important role in the occurrence and development of ccRCC. Nevertheless, the prognosis of ccRCC patients is very rarely based on these “immuno-miRs”. Our aim was thus to determine the relationship between immune-related miRNA signatures and ccRCC.

Methods

We downloaded the miRNA expression data from 521 KIRC and 71 normal tissues in The Cancer Genome Atlas (TCGA). We used “limma” package and univariate Cox regression analysis to identify differentially expressed miRNAs (DEMs) that related to overall survival (OS). We applied lasso and multivariate Cox regression analyses to construct a prognostic model based on immuno-miRs. We evaluated the performance of model by using the Kaplan-Meier method. Furthermore, Cox regression analysis was used to determine independent prognostic signatures in ccRCC.

Results

A total of 59 significant immuno-miRs were identified. We use univariate Cox regression analysis to acquire 18 immune-related miRNAs which were markedly related to OS of ccRCC patients in the training set. We then constructed the 9-immune-related-miRNA prognostic model (miR-21, miR-342, miR-149, miR-130b, miR-223, miR-365a, miR-9-1, and miR-146b) by using lasso and multivariate Cox regression. Further analysis suggested that the immune-related prognostic model could be an independent prognostic indicator for patients with ccRCC. The prognostic performance of the 9-immune-related-miRNA prognostic model was further validated successfully in the testing set.

Conclusions

We established a novel immune-based prognostic model of ccRCC based on potential prognostic immune-related miRNAs. Our results indicated that the 9-miRNA signature could be a practical and reliable prognostic tool for ccRCC.

Systematic Analysis of microRNA Biomarkers for Diagnosis, Prognosis, and Therapy in Patients With Clear Cell Renal Cell Carcinoma

The ever-increasing morbidity and mortality of clear cell renal cell carcinoma (ccRCC) urgently demands updated biomarkers. MicroRNAs (miRNAs) are involved in diverse biological processes such as cell proliferation, differentiation, apoptosis by regulating their target genes' expression. In kidney cancers, miRNAs have been reported to be involved in tumorigenesis and to be the diagnostic, prognostic, and therapeutic response biomarkers. Here, we performed a systematic analysis for ccRCC-related miRNAs as biomarkers by searching keywords in the NCBI PubMed database and found 118 miRNAs as diagnostic biomarkers, 28 miRNAs as prognostic biomarkers, and 80 miRNAs as therapeutic biomarkers in ccRCC. miRNA-21, miRNA-155, miRNA-141, miRNA-126, and miRNA-221, as significantly differentially expressed miRNAs between cancer and normal tissues, play extensive roles in the cell proliferation, differentiation, apoptosis of ccRCC. GO and KEGG enrichment analysis of these miRNAs' target genes through Metascape showed these target genes are enriched in Protein Domain Specific Binding (GO:0019904). In this paper, we identified highly specific miRNAs in the pathogenesis of ccRCC and explored their potential applications for diagnosis, prognosis, and treatment of ccRCC.

Metformin: the updated protective property in kidney disease

Metformin is a frontline hypoglycemic agent, which is mainly prescribed to manage type 2 diabetes mellitus with obesity. Emerging evidence suggests that metformin also exerts protective effects against various kidney diseases. Some postulate that kidney disease is actually a metabolic disease, accompanied by nonresolving pathophysiologic pathways controlling oxidative stress, endoplasmic reticulum stress, inflammation, lipotoxicity, fibrosis, and senescence, as well as insufficient host defense mechanisms such as AMP-activated protein kinase (AMPK) signaling and autophagy. Metformin may interfere with these pathways by orchestrating AMPK signaling and AMPK-independent pathways to protect the kidneys from injury. Furthermore, the United States Food and Drug Administration declared metformin is safe for patients with mild or moderate kidney impairment in 2016, assuaging some conservative attitudes about metformin management in patients with renal insufficiency and broadening the scope of research on the renal protective effects of metformin. This review focuses on the molecular mechanisms by which metformin imparts renal protection and its potential in the treatment of various kidney diseases.

Anticancer mechanisms of metformin: A review of the current evidence

Metformin, a US Food and Drug Administration-approved "star" drug used for diabetes mellitus type 2, has become a topic of increasing interest to researchers due to its anti-neoplastic effects. Growing evidence has demonstrated that metformin may be a promising chemotherapeutic agent, and several clinical trials of metformin use in cancer treatment are ongoing. However, the anti-neoplastic effects of metformin and its underlying mechanisms have not been fully elucidated. In this review, we present the newest findings on the anticancer activities of metformin, and highlight its diverse anticancer mechanisms. Several clinical trials, as well as the limitations of the current evidence are also demonstrated. This review explores the crucial roles of metformin and provides supporting evidence for the repurposing of metformin as a treatment of cancer.

TGF-β1 Induces Epithelial-Mesenchymal Transition of Chronic Sinusitis with Nasal Polyps through MicroRNA-21

OBJECTIVES

To characterize the epithelial-mesenchymal transition (EMT) in chronic rhinosinusitis with nasal polyps (CRSwNP) and to investigate the mechanism by which microRNA-21 (miR-21) regulates EMT in CRSwNP.

METHOD

(1) Tissue experiments: Mucosa tissues were collected from 13 patients with CRSwNP and 12 patients with CRS without nasal polyps (CRSsNP), as well as 11 patients without CRS (controls). Protein localization and quantification were achieved by immunofluorescence staining and Western blotting, involving the epithelial marker protein E-cadherin and the mesenchymal marker proteins α-smooth muscle actin (α-SMA), fibronectin, and vimentin. Quantitative RT-PCR was used to detect the relative expression levels of miR-21 and TGF-β1 mRNAs. (2) Cellular experiments: Primary human nasal epithelial cells (PHNECs) treated with TGF-β1, or TGF-β1 with miR-21 inhibitor, or miR-21 mimics alone were observed for morphology changes under a phase-contrast microscope. The expression levels of epithelial/mesenchymal marker proteins were determined as aforementioned. PTEN and phosphorylated Akt were detected by Western blotting.

RESULTS

(1) Tissue experiments: Compared with the CRSsNP and control groups, the expression of E-cadherin was downregulated in the CRSwNP group, whereas the expression of TGF-β1, α-SMA, fibronectin, and vimentin was upregulated. The expression levels of miR-21 and TGF-β1 mRNAs in CRSwNP were significantly higher than those in CRSsNP and controls. (2) Cellular experiments: TGF-β1 induced EMT-like transformation in PHNECs, featured by changes in cell morphology and upregulation of mesenchymal proteins and miR-21. The miR-21 inhibitor, as well as the Akt-specific -inhibitor, suppressed TGF-β1-induced EMT. Mechanically, downregulation of miR-21 resulted in increased PTEN and decreased Akt phosphorylation. Furthermore, overexpression of miR-21 had the opposite effects.

CONCLUSIONS

Our findings suggest that the TGF-β1-miR-21-PTEN-Akt axis may contribute to the pathogenesis of CRSwNP. miR-21 might be a reliable target for treating nasal polyp genesis through EMT suppression. Moreover, miR-21 inhibitors could be a novel class of antipolyp drug that modulates PTEN expression and Akt activation. In addition, further investigation regarding the reason underlying miR-21 overexpression in CRSwNP could provide a molecular target for novel treatment strategies for nasal polyposis.

Metformin Induces Different Responses in Clear Cell Renal Cell Carcinoma Caki Cell Lines

Clear cell renal cell carcinoma (ccRCC) is the most common and lethal form of urological cancer diagnosed globally. Mutations of the von Hippel-Lindau (VHL) tumor-suppressor gene and the resultant overexpression of hypoxia-inducible factor (HIF)-1α protein are considered hallmarks of ccRCC. Persistently activated HIF-1α is associated with increased cell proliferation, angiogenesis, and epithelial–mesenchymal transition (EMT), consequently leading to ccRCC progression and metastasis to other organs. However, the VHL status alone cannot predict the differential sensitivity of ccRCC to cancer treatments, which suggests that other molecular differences may contribute to the differential response of ccRCC cells to drug therapies. In this study, we investigated the response to metformin (an antidiabetic drug) of two human ccRCC cell lines Caki-1 and Caki-2, which express wild-type VHL. Our findings demonstrate a differential response between the two ccRCC cell lines studied, with Caki-2 cells being more sensitive to metformin compared to Caki-1 cells, which could be linked to the differential expression of HIF-1α despite both cell lines carrying a wild-type VHL. Our study unveils the therapeutic potential of metformin to inhibit the progression of ccRCC in vitro. Additional preclinical and clinical studies are required to ascertain the therapeutic efficacy of metformin against ccRCC.

Metformin Treatment Suppresses Melanoma Cell Growth and Motility Through Modulation of microRNA Expression

Melanoma is a highly aggressive cancer with high mortality in advanced stages. Metformin is an oral biguanide drug used for diabetes and has demonstrated positive effects on cancer prevention and treatment. Herein, we found that metformin significantly suppressed melanoma cancer cell motility and growth through inducing cell cycle arrest at the G2/M phase and promoting cell apoptosis. Using the next-generation sequencing approach, we identified three upregulated microRNAs (miRNA; miR-192-5p, miR-584-3p, and miR-1246) in melanoma cells treated with metformin. Among these, we examined the roles of miR-192-5p and miR-584-3p and discovered that they significantly suppressed melanoma cell motility. Furthermore, they inhibited melanoma cell growth through destroying cell cycle progression and inducing cell apoptosis. Using microarray and bioinformatics approaches for identifying putative target genes, Epidermal growth factor (EGF) containing fibulin-like extracellular matrix protein 1 (EFEMP1) gene for miR-192-5p and an isoform of the secretory carrier membrane proteins (SCAMP3) gene for miR-584-3p could be silenced through targeting their 3′UTR region directly. EFEMP1 and SCAMP3 knockdown significantly suppressed melanoma cell growth, but only EFEMP1 knockdown inhibited its motility abilities. Our findings indicated that miR-192-5p and miR-584-3p might contribute to metformin-induced growth and motility suppression in melanoma cells through silencing their target genes EFEMP1 and SCAMP3.

Molecular Mechanisms of Metformin for Diabetes and Cancer Treatment

Metformin has been the first-line drug treatment for hyperglycemia and insulin resistance for over 50 years. However, the molecular basis of its therapeutic role remained incompletely understood. Recent advances demonstrate that metformin could exert its glucose-lowering effect by multiple mechanisms, including activation of 5′-AMP-activated protein kinase, decreasing production of cyclic AMP, suppressing mitochondrial complex I of the electron transport chain, targeting glycerophosphate dehydrogenase, and altering the gut microbiome. In addition, epidemiological and clinical observation studies suggest that metformin reduced cancer risk in patients with type 2 diabetes and improved survival outcome of human cancers. Experimental studies have shown that this drug can inhibit cancer cell viability, growth, and proliferation through inhibiting mTORC1 signaling and mitochondrial complex I, suggesting that it may be a promising drug candidate for malignancy. Here, we summarize recent progress in studies of metformin in type 2 diabetes and tumorigenesis, which provides novel insight on the therapeutic development of human diseases.

MicroRNA-21 promotes TGF-β1-induced epithelial-mesenchymal transition in gastric cancer through up-regulating PTEN expression

This study aimed to explore the effects of miR-21 and PTEN/Akt signaling pathway on TGF-β1-induced epithelial-mesenchymal transition (EMT) in gastric cancer (GC). GC tissues and adjacent tissues were collected from 83 patients. The qRT-PCR assay was performed to detect miR-21 expression. The expressions of PTEN, Akt and p-Akt were detected by immunohistochemistry. After 48 h of treatment with TGF-β1 (10 ng/mL), the SGC-7901 and KATO-III cells were divided into the blank, negative control (NC), miR-21 inhibitors, PTEN-siRNA and miR-21 inhibitors + PTEN-siRNA groups. EMT related factors and PTEN expressions were detected by qRT-PCR assay and Western blotting. The scratch test was conducted to observe cell migration. Xenograft tumor model in nude mice was used to evaluate the effects of miR-21 on EMT of GC cells in vivo. In GC tissues, the expressions of miR-21, Akt and p-Akt were up-regulated, while PTEN expression was down-regulated. Gene and protein expressions of E-cadherin and PTEN in the miR-21 inhibitors group were higher than the blank, NC, PTEN-siRNA and miR-21 inhibitors + PTEN-siRNA groups, while the expressions of N-cadherin, β-catenin, Vimentin and Slug in the miR-21 inhibitors group were lower than other groups. MiR-21 inhibitors significantly inhibit cell migration and invasion in GC cell lines. In vivo xenograft experiment revealed that miR-21 inhibitor inhibits the growth of transplanted tumor through up-regulating E-cadherin and PTEN expressions and down-regulating the expressions of N-cadherin, β-catenin, Vimentin and Slug. These results suggest that miR-21 could promote TGF-β1-induced EMT in GC cells through up-regulating PTEN expression.

Emerging Role of MicroRNAs in mTOR Signaling

Mechanistic target of rapamycin (mTOR) is a conserved serine/threonine kinase that plays a critical role in the control of cellular growth and metabolism. Hyperactivation of mTOR pathway is common in human cancers, driving uncontrolled proliferation. MicroRNA (miRNA) is a class of short noncoding RNAs that regulate the expression of a wide variety of genes. Deregulation of miRNAs is a hallmark of cancer. Recent studies have revealed interplays between miRNAs and the mTOR pathway during cancer development. Such interactions appear to provide a fine-tuning of various cellular functions and contribute qualitatively to the behavior of cancer. Here we provide an overview of current knowledge regarding the reciprocal relationship between miRNAs and mTOR pathway: regulation of mTOR signaling by miRNAs and control of miRNA biogenesis by mTOR. Further research in this area may prove important for the diagnosis and therapy of human cancer.

MiRNA-21 mediates the antiangiogenic activity of metformin through targeting PTEN and SMAD7 expression and PI3K/AKT pathway

Metformin, an anti-diabetic drug commonly used for type 2 diabetes therapy, is associated with anti-angiogenic effects in conditions beyond diabetes. miR-21 has been reported to be involved in the process of angiogenesis. However, the precise regulatory mechanisms by which the metformin-induced endothelial suppression and its effects on miR-21-dependent pathways are still unclear. Bioinformatic analysis and identification of miR-21 and its targets and their effects on metformin-induced antiangiogenic activity were assessed using luciferase assays, quantitative real-time PCR, western blots, scratch assays, CCK-8 assays and tubule formation assays. In this study, miR-21 was strikingly downregulated by metformin in a time- and dose-dependent manner. miR-21 directly targeted the 3′-UTR of PTEN and SMAD7, and negatively regulated their expression. Overexpression of miR-21 abrogated the metformin-mediated inhibition of endothelial cells proliferation, migration, tubule formation and the TGF-β-induced AKT, SMAD- and ERK-dependent phosphorylations, and conversely, down-regulation of miR-21 aggravated metformin’s action and revealed significant promotion effects. Our study broadens our understanding of the regulatory mechanism of miR-21 mediating metformin-induced anti-angiogenic effects, providing important implications regarding the design of novel miRNA-based therapeutic strategies against angiogenesis.

Potential role for metformin in urologic oncology

Metformin is one of the most commonly used drugs worldwide. It is currently considered first-line pharmacological agent for management of diabetes mellitus type 2. Recent studies have suggested that metformin may have further benefits, especially in the field of urologic oncology. Use of metformin has been shown to be associated with decreased incidence and improved outcomes of prostate, bladder, and kidney cancer. These studies suggest that metformin does have a future role in the prevention and management of urologic malignancies. In this review, we will discuss the latest findings in this field and its implications on the management of urologic oncology patients.