MicroRNA-34a and microRNA-21 play roles in the chemopreventive effects of 3,6-dihydroxyflavone on 1-methyl-1-nitrosourea-induced breast carcinogenesis

Identification of novel broad-spectrum antiviral drugs targeting the N-terminal domain of the FIPV nucleocapsid protein

Coronaviruses pose serious threats to human and animal health worldwide, of which their structural nucleocapsid (N) proteins play multiple key roles in viral replication. However, the structures of animal coronavirus N proteins are poorly understood, posing challenges for research on their functions and pathogenic mechanisms as well as the development of N protein-based antiviral drugs. Therefore, N proteins must be further explored as potential antiviral targets. We determined the structure of the NNTD of feline infectious peritonitis virus (FIPV) and identified 3,6-dihydroxyflavone (3,6- DHF) as an effective N protein inhibitor. 3,6-DHF successfully inhibited FIPV replication in CRFK cells, showing broad-spectrum activity and effectiveness against drugresistant strains. Our study provides important insights for developing novel broadspectrum anti-coronavirus drugs and treating infections caused by drug-resistant mutant strains.

In-vitro inhibition of NLRP3 inflammasome by 3,6-dihydroxyflavone (3,6-DHF): a therapeutic strategy for the treatment of chronic inflammatory and autoimmune diseases

Nucleotide-binding oligomerization domain (NOD)-like receptor family pyrin domain containing 3 (NLRP3) inflammasome complex has an important role in immune system and its abnormal activation is associated with the pathogenesis of various inflammatory and auto-immune diseases. The study reveals the anti-inflammatory effects of 3,6-dihydroxyflavone (3,6-DHF). Here, we aimed to determine the inhibitory effects of 3,6-DHF on NLRP3 inflammasome and its associated components, thereby determining the signaling pathways involved in the inhibition. Reactive oxygen species (ROS) and nitric oxide (NO) were quantified by chemiluminescence and Griess methods, respectively. Inflammatory cell model was induced in human leukemic monocytes (THP-1). mRNA levels were estimated through real-time RT-PCR, protein expressions were evaluated by protein slot blot and immunocytochemistry, MTT and alamar blue assays were employed for toxicity studies. The compound 3,6-DHF was found to be the potent inhibitor of NLRP3 inflammasome by targeting the molecules involve in its activation pathway. Anti-inflammatory effects were revealed by inhibition of ROS and NO, reduction in the transcription of caspase-1, ASC, IL-1β and TLR-4 was observed along with the marked inhibition of NLRP3, IL-18, NF-κB and pNF-κB at translational level. 3,6-DHF was non-toxic on normal human fibroblast (BJ) and THP-1 cells and, could be a potential therapeutic agent in NLRP3 inflammasome driven diseases.

67-kDa Laminin Receptor-Mediated Cellular Sensing System of Green Tea Polyphenol EGCG and Functional Food Pairing

The body is equipped with a “food factor-sensing system” that senses food factors, such as polyphenols, sulfur-containing compounds, and vitamins, taken into the body, and plays an essential role in manifesting their physiological effects. For example, (–)-epigallocatechin-3-O-gallate (EGCG), the representative catechin in green tea (Camellia sinensi L.), exerts various effects, including anti-cancer, anti-inflammatory, and anti-allergic effects, when sensed by the cell surficial protein 67-kDa laminin receptor (67LR). Here, we focus on three representative effects of EGCG and provide their specific signaling mechanisms, the 67LR-mediated EGCG-sensing systems. Various components present in foods, such as eriodictyol, hesperetin, sulfide, vitamin A, and fatty acids, have been found to act on the food factor-sensing system and affect the functionality of other foods/food factors, such as green tea extract, EGCG, or its O-methylated derivative at different experimental levels, i.e., in vitro, animal models, and/or clinical trials. These phenomena are observed by increasing or decreasing the activity or expression of EGCG-sensing-related molecules. Such functional interaction between food factors is called “functional food pairing”. In this review, we introduce examples of functional food pairings using EGCG.

Phytochemicals mediated modulation of microRNAs and long non-coding RNAs in cancer prevention and therapy

MicroRNAs (miRNAs) and long noncoding RNAs (lncRNAs) are two main categories of noncoding RNAs (ncRNAs) that can influence essential biological functions in various ways, as well as their expression and function are tightly regulated in physiological homeostasis. Additionally, the dysregulation of these ncRNAs seems to be crucial to the pathogenesis of human diseases. The latest findings indicate that ncRNAs execute vital roles in cancer initiation and progression, and the cancer phenotype can be reversed by modulating their expression. Available scientific discoveries suggest that phytochemicals such as polyphenols, alkaloids, terpenoids, and organosulfur compounds can significantly modulate multiple cancer-associated miRNAs and lncRNAs, thereby inhibiting cancer initiation and development. However, despite promising outcomes of experimental research, only a few clinical trials are currently being conducted to evaluate the therapeutic effectiveness of these compounds. Nevertheless, understanding phytochemical-mediated ncRNA regulation in cancer and the underlying molecular mechanisms on tumor pathophysiology can aid in the development of novel therapeutic strategies to combat this deadly disease.

Regulation of microRNA-21 expression by natural products in cancer

Natural products have been of much interest in research studies owing to their wide pharmacological applications, chemical diversity, low side effects, and multitarget activities. Examples of these compounds include matrine, sulforaphane, silibinin, curcumin, berberin, resveratrol, and quercetin. Some of the present anticancer drugs, such as taxol, vincristine, vinblastine, and doxorubicin are also derived from natural products. The anti-carcinogenic effects of these products are partly mediated through modulation of microRNA-21 (miR-21) expression. To date, numerous downstream targets of miR-21 have been recognized, which include phosphatase and tensin homolog (PTEN), ras homolog gene family member B (RHOB), phosphoinositide 3-kinase/protein kinase B (PI3K/Akt), programmed cell death 4 (PDCD4), signal transducer and activator of transcription (STAT)-3, and nuclear factor kappa B (NF-κB) pathways. These signaling pathways, their regulation by oncomiR-21 in cancer, and the modulating impact of natural products are the main focus of this review.

Inhibitory effect of flavonoid xanthomicrol on triple-negative breast tumor via regulation of cancer-associated microRNAs

Breast cancer is the leading cause of cancer death in women worldwide. Due to the side effects of current chemo-reagents on healthy tissues, it is essential to search for alternative compounds with less toxicity and better efficacy. In the present study, we have investigated the anticancer effects of flavonoid xanthomicrol on the mice breast cancer model using MTT assay, cell cycle and Annexin/PI analysis, colony formation assay, H&E staining, immunohistochemistry, and miRNA analysis. Our results demonstrated that xanthomicrol decreased the cell viability and clonogenic capability, induced G1-arrest and apoptosis in the breast cancer cells in vitro, and caused a significant reduction in the volume and weight of mice tumors in vivo. In addition, xanthomicrol reduced the expression of TNFα, VEGF, MMP9, and Ki67, while upregulating the expression of apoptotic markers such as Bax, caspase3, and caspase9. Finally, the expression of miR21, miR27, and miR125, known as oncomirs, decreased significantly after xanthomicrol administration, while the expression of miR29 and miR34, functioning as tumor suppressors, increased significantly (p < .001). Our data demonstrated that xanthomicrol can induce apoptosis and suppress angiogenesis in breast cancer cells due to its inhibitory effect on oncomirs and its stimulatory effect on tumor suppressor miRNAs.

Breast Cancer Primary Prevention and Diet: An Umbrella Review

Introduction: Many studies have been published, but none have pooled the useful evidence available in the literature to produce guidelines and health policies promoting healthy eating styles to prevent breast cancer (BC). The present study aimed to summarize the evidence produced to date, taking a judicious, critical approach to the quality of the studies analyzed. Methods: An umbrella review method was adopted, which is a systematic review of second-level studies, meta-analyses and literature reviews. Results: In all, 48 studies were considered: 32 meta-analyses, 4 pooled analyses, 5 systematic reviews, and 7 qualitative reviews. A higher intake of total meat, or red or processed meats, or foods with a high glycemic index, or eggs would seem to be associated with a higher risk of BC. Some foods, such as vegetables, would seem instead to have an inverse association with BC risk. One meta-analysis revealed an inverse association between citrus fruit and mushroom consumption and BC. Some nutrients, such as calcium, folate, vitamin D, lignans and carotenoids, also seem to be inversely associated with BC risk. The evidence is still conflicting as concerns exposure to other dietary elements (e.g., polyunsaturated fatty acids, dairy foods). Conclusion: Nutrition is one of the most modifiable aspects of people's lifestyles and dietary choices can affect health and the risk of cancer. Overall, adhering to a healthy eating style may be associated with a significant reduction in the risk of BC.

miR-520b Promotes Breast Cancer Stemness Through Hippo/YAP Signaling Pathway

Introduction

The breast cancer stem cells contribute to the initiation, progression, recurrence, metastasis as well as resistance of breast cancer. However, the mechanisms underlying the maintenance of breast cancer stemness have not been fully understood.

Materials and methods

TCGA and GEO data were used for measuring miR-520b expression in breast cancer tissues. Kaplan-meier analysis was used for determining the relationship between miR-520b expression level and the prognosis of patients. Genetic manipulation was performed by lentivirus system and miR-520b inhibitor was used for knockdown of miR-520b. qRT-PCR and Western blot were employed to determine the mRNA and protein levels, respectively. The stemness and EMT (Epithelial to mesenchymal transition) were assessed by sphere-formation and transwell assay as well as the expression of the related markers. The target genes of miR-520b were identified using the online database starBase V3.0.

Results

miR-520b is upregulated in cancer tissues of breast cancer patients and predicts poor prognosis. Upregulation of miR-520b was found in breast cancer stem cells. Ectopic expression of miR-520b promotes the stemness of the breast cancer cells, conversely, depletion of miR-520b attenuates the stemness of these cells. miR-520b positively regulates Hippo/YAP signaling pathway and overexpression of LAST2 abolished the effect of miR-520b on the stemness of breast cancer cells.

Conclusion

miR-520b promotes the stemness of breast cancer patients by activating Hippo/YAP signaling via targeting LATS2.

Cellular plasticity and metastasis in breast cancer: a pre- and post-malignant problem

As a field we have made tremendous strides in treating breast cancer, with a decline in the past 30 years of overall breast cancer mortality. However, this progress is met with little affect once the disease spreads beyond the primary site. With a 5-year survival rate of 22%, 10-year of 13%, for those patients with metastatic breast cancer (mBC), our ability to effectively treat wide spread disease is minimal. A major contributing factor to this ineffectiveness is the complex make-up, or heterogeneity, of the primary site. Within a primary tumor, secreted factors, malignant and pre-malignant epithelial cells, immune cells, stromal fibroblasts and many others all reside alongside each other creating a dynamic environment contributing to metastasis. Furthermore, heterogeneity contributes to our lack of understanding regarding the cells' remarkable ability to undergo epithelial/non-cancer stem cell (CSC) to mesenchymal/CSC (E-M/CSC) plasticity. The enhanced invasion & motility, tumor-initiating potential, and acquired therapeutic resistance which accompanies E-M/CSC plasticity implicates a significant role in metastasis. While most work trying to understand E-M/CSC plasticity has been done on malignant cells, recent evidence is emerging concerning the ability for pre-malignant cells to undergo E-M/CSC plasticity and contribute to the metastatic process. Here we will discuss the importance of E-M/CSC plasticity within malignant and pre-malignant populations of the tumor. Moreover, we will discuss how one may potentially target these populations, ultimately disrupting the metastatic cascade and increasing patient survival for those with mBC.

Relations between approved platinum drugs and non-coding RNAs in mesothelioma

Malignant mesothelioma diseases feature an increasing risk due to their severe forms and their association with asbestos exposure. Platinum(II) complexes such as cisplatin and carboplatin are clinically approved for the therapy of mesothelioma often in combination with antimetabolites such as pemetrexed or gemcitabine. It was observed that pathogenic properties of mesothelioma cells and the response of mesothelioma tumors towards platinum-based drugs are strongly influenced by non-coding RNAs, in particular, by small microRNAs (miRNAs) and long non-coding RNAs (lncRNAs). These non-coding RNAs controlled drug sensitivity and the development of tumor resistance towards platinum drugs. An overview of the interactions between platinum drugs and non-coding RNAs is given and the influence of non-coding RNAs on platinum drug efficacy in mesothelioma is discussed. Suitable non-coding RNA-modulating agents with potentially beneficial effects on cisplatin treatment of mesothelioma diseases are mentioned. The understanding of mesothelioma diseases concerning the interactions of non-coding RNAs and platinum drugs will optimize existing therapy schemes and pave the way to new treatment options in future.

Interplay of non-coding RNAs and approved antimetabolites such as gemcitabine and pemetrexed in mesothelioma

Gemcitabine and pemetrexed are clinically approved antimetabolites for the therapy of mesothelioma diseases. These drugs are often applied in combination with platinum complexes and other drugs. The activity of antimetabolites depended on the expression levels of certain non-coding RNAs, in particular, of small microRNAs (miRNAs) and long non-coding RNAs (lncRNAs). The development of tumor resistance towards antimetabolites was regulated by non-coding RNAs. An overview of the interplay between gemcitabine/pemetrexed antimetabolites and non-coding RNAs in mesothelioma is provided. Further to this, various non-coding RNA-modulating agents are discussed which displayed positive effects on gemcitabine or pemetrexed treatment of mesothelioma diseases. A detailed knowledge of the connections of non-coding RNAs with antimetabolites will be constructive for the design of improved therapies in future.

MicroRNA-34 family in breast cancer: from research to therapeutic potential

MicroRNA (miRNA)-34 family (miR-34s), including miR-34a/b/c, is the most well studied non-coding RNAs that regulate gene expression post-transcriptionally. The miR-34s mediates the tumor suppressor function of p53 in the pathogenesis of breast cancer by targeting different oncogenes. This review focuses on the anti-oncogenic regulation of the miR-34s, emphasizing the major signaling pathways that are involved in the modulation of miR-34s in breast cancer. Moreover, it highlights how epigenetic modification by the p53/miR-34s axis regulates the proliferation, invasiveness, chemoresistance, and sternness of breast cancer. A better understanding of the molecular mechanisms of miR-34s will open new opportunities for the development of novel therapeutic strategies and define a new approach in identifying potential biomarkers for early diagnosis of breast cancer.

Simultaneous downregulation of miR-21 and miR-155 through oleuropein for breast cancer prevention and therapy

Breast cancer (BC) is the leading cause of cancer mortality in women worldwide. It recently was proven that miRNAs play a critical role in BC development. The use of natural agents for control of cancer by modulating miRNAs is promising. Oleuropein is a natural polyphenolic agent with anti-neoplastic properties and is well tolerated by humans. This study was undertaken to determine the therapeutic effects of oleuropein through modulation of master oncomiRs (miR-21 and miR-155) in BC cells. The present study provides the first link between miRNA and oleuropein as a mechanism in BC. MCF-7 cells were tested with and without oleuropein and the cell viability, apoptosis, and migration were examined. The effect of oleuropein on miR-21 and miR-155 expression was assessed through qRT-PCR. It was found that oleuropein induced apoptosis and retarded cell migration and invasion in a dose-dependent manner in the human MCF7 BC cell line. It was observed that oleuropein significantly decreased expression of both miR-21 and miR-155 over time in a dose-dependent manner. These results demonstrate that oleuropein is a potential therapeutic and preventive agent for BC. Oleuropein exhibits an anti-cancer effect by modulation of tumor suppressor gene expression, which is targeted by oncomiRs.

Breast cancer stem cells-from origins to targeted therapy

Breast cancer is marked as one of the leading causes of malignancy-related morbidities worldwide. In spite of aggressive interventions, the inevitability of relapse and metastasis severely impede survival rates. Mounting evidence highlight the insidious role of cancer stem cells (CSCs), a small but significant subpopulation of undifferentiated cells that drive tumour progression, spread and resistance to conventional therapy. The nature and significance of breast CSCs remains poorly understood, and even disputed by many researchers. This review discusses the origins, biomarkers, signalling pathways, regulatory mechanisms, and targeted therapy of breast CSCs.

3,6-Dihydroxyflavone regulates microRNA-34a through DNA methylation

BACKGROUND

Breast cancer is the common cancer in China. In previous study, we determined that 3,6-dihydroxyflavone (3,6-DHF) increases miR-34a significantly in breast carcinogenesis, but the mechanism remains unclear.

METHODS

We used qRT-PCR to analyze miR-34a and ten-eleven translocation (TET)1, TET2, TET3 levels in breast cancer cells. With a cellular breast carcinogenesis model and an experimental model of carcinogenesis in rats, TET1 levels were evaluated by western blot analysis and immunofluorescence. TET1 and 5hmC (5-hydroxymethylcytosine) levels were evaluated by immunofluorescence in nude mouse xenografts of MDA-MB-231 cells. Chromatin immunoprecipitation(ChIP) assayed for TET1 on the TET1 promoter, and dot blot analysis of DNA 5hmC was performed in MDA-MB-231 cells. We evaluated the mechanism of 3,6-DHF on the expression of tumor suppressor miR-34a by transfecting them with DNA methyltransferase (DNMT)1 plasmid and TET1 siRNA in breast cancer cells. Methylation-specific PCR detected methylation of the miR-34a promoter.

RESULTS

First, we found that 3,6-DHF promotes the expression of TET1 during carcinogen-induced breast carcinogenesis in MCF10A cells and in rats. 3,6-DHF also increased TET1 and 5hmC levels in MDA-MB-231 cells. Further study indicated that TET1 siRNA and pcDNA3/Myc-DNMT1 inhibited the 3,6-DHF reactivation effect on expression of miR-34a in breast cancer cells. Methylation-specific PCR assays indicated that TET1 siRNA and pcDNA3/Myc-DNMT1 inhibit the effect of 3,6-DHF on the demethylation of the miR-34a promoter.

CONCLUSIONS

Our study showed that 3,6-DHF effectively increases TET1 expression by inhibiting DNMT1 and DNA hypermethylation, and consequently up-regulates miR-34a in breast carcinogenesis.

Targeting microRNAs: a new action mechanism of natural compounds

Unlike genetics, epigenetics involves the modification of genome without changes in DNA sequences, including DNA methylation, histone modification, chromatin remodeling and noncoding RNA regulation. MicroRNA (miRNA), a member of noncoding RNAs superfamily, participates in RNA interference through a unique mechanism. Currently, microRNAs have been found to be regulated by some natural compounds. Through altering the expression of miRNAs and influencing the downstream signaling pathways or target genes, several natural compounds exhibit its bioactivity in the prevention, diagnosis, therapy, prognosis and drug resistance of human diseases, such as cancer. In this review, several natural compounds and their studies about miRNA-related action mechanism were summarized. These studies provide a new insight into action mechanism by which natural compound exerts its bioactivity and a novel treatment strategy, demonstrating natural compound a promising remedy for clinical treatments.

Current state of phenolic and terpenoidal dietary factors and natural products as non-coding RNA/microRNA modulators for improved cancer therapy and prevention

The epigenetic regulation of cancer cells by small non-coding RNA molecules, the microRNAs (miRNAs), has raised particular interest in the field of oncology. These miRNAs play crucial roles concerning pathogenic properties of cancer cells and the sensitivity of cancer cells towards anticancer drugs. Certain miRNAs are responsible for an enhanced activity of drugs, while others lead to the formation of tumor resistance. In addition, miRNAs regulate survival and proliferation of cancer cells, in particular of cancer stem-like cells (CSCs), that are especially drug-resistant and, thus, cause tumor relapse in many cases. Various small molecule compounds were discovered that target miRNAs that are known to modulate tumor aggressiveness and drug resistance. This review comprises the effects of naturally occurring small molecules (phenolic compounds and terpenoids) on miRNAs involved in cancer diseases.

3,6-dihydroxyflavone suppresses the epithelial-mesenchymal transition in breast cancer cells by inhibiting the Notch signaling pathway

The epithelial to mesenchymal transition (EMT) is a critical developmental program in cancer stem cell (CSC) maintenance and in cancer metastasis. Here, our study found that 3,6-DHF could effectively inhibit EMT in BC cells in vitro and in vivo. 3,6-DHF effectively inhibits the formation and proliferation of BCSCs, and consequently reduces the tumor-initiating capacity of tumor cells in NOD/SCID mice. Optical in vivo imaging of cancer metastasis showed that 3,6-DHF administration suppresses the lung metastasis of BC cells in vivo. Further studies indicated that 3,6-DHF down-regulates Notch1, NICD, Hes-1 and c-Myc, consequently decreasing the formation of the functional transcriptional unit of NICD-CSL-MAML, causing Notch signaling inactivation in BC cells. Over-expression of Notch1 or inhibition of miR-34a significantly reduced the inhibitory effects of 3,6-DHF on EMT, CSCs, as well as cells migration and invasion in BC cells. These data indicated that 3,6-DHF effectively inhibits EMT and CSCs, as well as cells migration and invasion in BC cells, in which miR-34a-mediated Notch1 down-regulation plays a crucial role.

The altered microRNA profile in andrographolide-induced inhibition of hepatoma tumor growth

BACKGROUND

MicroRNAs (miRNAs) have been reported to play critical roles in regulating gene expression in tumor development. Natural compound andrographolide (Andro), isolated from medicinal herb Andrographis paniculata, was reported to inhibit hepatoma tumor growth in our previous studies. The present study aims to observe the altered miRNAs profile and related signaling pathways involved in Andro-induced inhibition on hepatoma tumor growth.

RESULTS

The inhibition on hepatoma tumor growth induced by Andro (10mg/kg) was found in a xenograft mouse tumor model in vivo. The results of miRNAs chip analysis showed that the expression of 22 miRNAs was increased, whereas the expression of other 10 miRNAs was decreased after Andro treatment. Further, the increased expression of miR-222-3p, miR-106b-5p, miR-30b-5p, and miR-23a-5p was confirmed in hepatoma Hep3B and SMCC7721 cells in vitro after cells were treated with Andro (50μM) for the indicated time. Functional annotation of the target genes based on the differentially expressed miRNAs demonstrated that the majority of the genes were involved in a variety of signaling pathways, including miRNAs in cancer, mitogen-activated protein kinases (MPAKs), focal adhesion. Furthermore, the expression of 24 target genes (total 31) involved in above signaling pathways based on miRNAs analysis was found to be consistent with the alteration of miRNAs.

CONCLUSIONS

The results demonstrate that Andro alters the expression of miRNAs profile and downstream signals, which may contribute to its inhibition on hepatoma tumor growth.

MiRNA 34a: a therapeutic target for castration-resistant prostate cancer

INTRODUCTION

Development of a therapy for bone metastases is of paramount importance for castration-resistant prostate cancer (CRPC). The osteomimetic properties of CRPC confer a propensity to metastasize to osseous sites. Micro-ribonucleic acid (miRNA) is non-coding RNA that acts as a post-transcriptional regulator of multiple proteins and associated pathways. Therefore identification of miRNAs could reveal a valid third generation therapy for CRPC.

AREAS COVERED

miR34a has been found to play an integral role in the progression of prostate cancer, particularly in the regulation of metastatic genes involved in migration, intravasation, extravasation, bone attachment and bone homeostasis. The correlation between miR34a down-regulation and metastatic progression has generated substantial interest in this field.

EXPERT OPINION

Examination of the evidence reveals that miR34a is an ideal target for gene therapy for metastatic CRPC. We also conclude that future studies should focus on the effects of miR34a upregulation in CRPC with respect to migration, translocation to bone micro-environment and osteomimetic phenotype development. The success of miR34a as a therapeutic is reliant on the development of appropriate delivery systems and targeting to the bone micro-environment. In tandem with any therapeutic studies, biomarker serum levels should also be ascertained as an indicator of successful miR34a delivery.

Role of apoptosis-related miRNAs in resveratrol-induced breast cancer cell death

Breast cancer is the most frequently diagnosed cancer in women, and one of the leading causes of cancer-related deaths worldwide. Recent evidences indicate that dietary agents such as resveratrol may inhibit cancer progression through modulation of microRNAs (miRNAs). We demonstrate that resveratrol regulates apoptotic and cell cycle machinery in breast cancer cells by modulating key tumor-suppressive miRNAs including miR-125b-5p, miR-200c-3p, miR-409-3p, miR-122-5p and miR-542-3p. Resveratrol-mediated miRNA modulation regulates key anti-apoptotic and cell cycle proteins including Bcl-2, X-linked inhibitor of apoptosis protein and CDKs, which are critical for its activity. Modulating miRNAs with mimics or inhibitors further validated a key role for miR-542-3p in MCF-7 and miR-122-5p in MDA-MB-231 breast cancer cell death in response to resveratrol. In conclusion, this study reveals novel miRNAs modulated by resveratrol that have a key role in breast cancer cell death.

Epigallocatechin-3-O-gallate up-regulates microRNA-let-7b expression by activating 67-kDa laminin receptor signaling in melanoma cells

MicroRNAs (miRNAs) are non-coding RNAs involved in various biological processes by regulating their target genes. Green tea polyphenol (−)-epigallocatechin-3-O-gallate (EGCG) inhibits melanoma tumor growth by activating 67-kDa laminin receptor (67LR) signaling. To examine the effect of EGCG on miRNA expression in melanoma cells, we performed miRNA microarray analysis. We showed that EGCG up-regulated miRNA-let-7b expression through 67LR in melanoma cells. The EGCG-induced up-regulation of let-7b led to down-regulation of high mobility group A2 (HMGA2), a target gene related to tumor progression. 67LR-dependent cAMP/protein kinase A (PKA)/protein phosphatase 2A (PP2A) signaling pathway activation was involved in the up-regulation of let-7b expression induced by EGCG. These findings provide a basis for understanding the mechanism of miRNA regulation by EGCG.

Pre-diagnostic polyphenol intake and breast cancer survival: the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort

The aim was to investigate the association between pre-diagnostic intakes of polyphenol classes (flavonoids, lignans, phenolic acids, stilbenes, and other polyphenols) in relation to breast cancer survival (all-cause and breast cancer-specific mortality). We used data from the European Prospective Investigation into Cancer and Nutrition cohort. Pre-diagnostic usual diet was assessed using dietary questionnaires, and polyphenol intakes were estimated using the Phenol-Explorer database. We followed 11,782 breast cancer cases from time of diagnosis until death, end of follow-up or last day of contact. During a median of 6 years, 1482 women died (753 of breast cancer). We related polyphenol intake to all-cause and breast cancer-specific mortality using Cox proportional hazard models with time since diagnosis as underlying time and strata for age and country. Among postmenopausal women, an intake of lignans in the highest versus lowest quartile was related to a 28 % lower risk of dying from breast (adjusted model: HR, quartile 4 vs. quartile 1, 0.72, 95 % CI 0.53; 0.98). In contrast, in premenopausal women, a positive association between lignan intake and all-cause mortality was found (adjusted model: HR, quartile 4 vs. quartile 1, 1.63, 95 % CI 1.03; 2.57). We found no association for other polyphenol classes. Intake of lignans before breast cancer diagnosis may be related to improved survival among postmenopausal women, but may on the contrary worsen the survival for premenopausal women. This suggests that the role of phytoestrogens in breast cancer survival is complex and may be dependent of menopausal status.

Breast Cancer/Stromal Cells Coculture on Polyelectrolyte Films Emulates Tumor Stages and miRNA Profiles of Clinical Samples

In this study, we demonstrate a method for controlling breast cancer cells adhesion on polyelectrolyte multilayer (PEM) films without the aid of adhesive proteins/ligands to study the role of tumor and stromal cell interaction on cancer biology. Numerous studies have explored engineering coculture of tumor and stromal cells predominantly using transwell coculture of stromal cells cultured onto coverslips that were subsequently added to tumor cell cultures. However, these systems imposed an artificial boundary that precluded cell-cell interactions. To our knowledge, this is the first demonstration of patterned coculture of tumor cells and stromal cells that captures the temporal changes in the miRNA signature as the breast tumor develops through various stages. In our study we used synthetic polymers, namely poly(diallyldimethylammonium chloride) (PDAC) and sulfonated poly(styrene) (SPS), as the polycation and polyanion, respectively, to build PEMs. Breast cancer cells attached and spread preferentially on SPS surfaces while stromal cells attached to both SPS and PDAC surfaces. SPS patterns were formed on PEM surfaces, by either capillary force lithography (CFL) of SPS onto PDAC surfaces or vice versa, to obtain patterns of breast cancer cells and patterned cocultures of breast cancer and stromal cells. In this study, we utilized cancer cells derived from two different tumor stages and two different stromal cells to effectively model a heterogeneous tumor microenvironment and emulate various tumor stages. The coculture model mimics the proliferative index (Ki67 expression) and tumor aggressiveness (HER-2 expression) akin to those observed in clinical tumor samples. We also demonstrated that our patterned coculture model captures the temporal changes in the miRNA-21 and miRNA-34 signature as the breast tumor develops through various stages. The engineered coculture platform lays groundwork toward precision medicine wherein patient-derived tumor cells can be incorporated within our in vitro models to identify potential pathways and drug treatment regimens for individual patients.

Phytochemical regulation of the tumor suppressive microRNA, miR-34a, by p53-dependent and independent responses in human breast cancer cells

The tumor suppressive microRNA miR-34a is transcriptionally regulated by p53 and shown to inhibit breast cancer cell proliferation as well as being a marker of increased disease free survival. Indole-3-carbinol (I3C) derived from cruciferous vegetables, artemisinin, extracted from the sweet wormwood plant, and artesunate, a semi-synthetic derivative of artemisinin, are phytochemicals with anti-tumorigenic properties however, little is known about the role of microRNAs in their mechanism of action. Human breast cancer cells expressing wild-type (MCF-7) or mutant p53 (T47D) were treated with a concentration range and time course of each phytochemical under conditions of cell cycle arrest as detected by flow cytometry to examine the potential connection between miR-34a expression and their anti-proliferative responses. Real-time PCR and western blot analysis of extracted RNA and total protein revealed artemsinin and artesunate increased miR-34a expression in a dose-dependent manner correlating with down-regulation of the miR-34a target gene, CDK4. I3C stimulation of miR-34a expression required functional p53, whereas, both artemisinin and artesunate up-regulated miR-34a expression regardless of p53 mutational status or in the presence of dominant negative p53. Phytochemical treatments inhibited the luciferase activity of a construct containing the wild-type 3'UTR of CDK4, but not those with a mutated miR-34a binding site, whereas, transfection of miR-34a inhibitors ablated the phytochemical mediated down-regulation of CDK4 and induction of cell cycle arrest. Our results suggest that miR-34a is an essential component of the anti-proliferative activities of I3C, artemisinin, and artesunate and demonstrate that both wild-type p53 dependent and independent pathways are responsible for miR-34a induction.

Mir-34: a new weapon against cancer?

The microRNA(miRNA)-34a is a key regulator of tumor suppression. It controls the expression of a plethora of target proteins involved in cell cycle, differentiation and apoptosis, and antagonizes processes that are necessary for basic cancer cell viability as well as cancer stemness, metastasis, and chemoresistance. In this review, we focus on the molecular mechanisms of miR-34a-mediated tumor suppression, giving emphasis on the main miR-34a targets, as well as on the principal regulators involved in the modulation of this miRNA. Moreover, we shed light on the miR-34a role in modulating responsiveness to chemotherapy and on the phytonutrients-mediated regulation of miR-34a expression and activity in cancer cells. Given the broad anti-oncogenic activity of miR-34a, we also discuss the substantial benefits of a new therapeutic concept based on nanotechnology delivery of miRNA mimics. In fact, the replacement of oncosuppressor miRNAs provides an effective strategy against tumor heterogeneity and the selective RNA-based delivery systems seems to be an excellent platform for a safe and effective targeting of the tumor.

MicroRNA-218 is upregulated in gastric cancer after cytoreductive surgery and hyperthermic intraperitoneal chemotherapy and increases chemosensitivity to cisplatin

AIM: To investigate the molecular mechanisms of miRNA in advanced gastric cancers (AGCs) before and after cytoreductive surgery (CRS) + hyperthermic intraperitoneal chemotherapy (HIPEC).

METHODS: A miRNA microarray containing human mature and precursor miRNA sequences was used to compare expression profiles in serum samples of 5 patients with AGC before and after CRS + HIPEC. The upregulation of miR-218 was confirmed by real-time reverse transcription polymerase chain reaction and its expression was analyzed in SGC7901 gastric cancer cells.

RESULTS: miRNA microarray chip analysis found that the level of miR-218 expression was upregulated more than 8 fold after CRS + HIPEC. Furthermore, miR-218 increased gastric cancer cell chemosensitivity to cisplatin in vitro and inhibited gastric cell tumor growth in nude mice in vivo (0.5 vs 0.78, P < 0.05).

CONCLUSION: Our results indicated that targeting miR-218 may provide a strategy for blocking the development of gastric cancer and reverse the multi-drug resistance of gastric cell lines.

Resveratrol inhibits breast cancer stem-like cells and induces autophagy via suppressing Wnt/β-catenin signaling pathway

Resveratrol, a natural polyphenolic compound, is abundantly found in plant foods and has been extensively studied for its anti-cancer properties. Given the important role of CSCs (Cancer Stem Cells) in breast tumorigenesis and progression, it is worth investigating the effects of resveratrol on CSCs. The article is an attempt to investigate the effects of resveratrol on breast CSCs. Resveratrol significantly inhibits the proliferation of BCSCs (breast cancer stem-like cells) isolated from MCF-7 and SUM159, and decreased the percentage of BCSCs population, consequently reduced the size and number of mammospheres in non-adherent spherical clusters. Accordingly, the injection of resveratrol (100 mg/kg/d) in NOD/SCID (nonobese diabetic/severe combined immunodeficient) mice effectively inhibited the growth of xenograft tumors and reduced BCSC population in tumor cells. After the reimplantation of primary tumor cells into the secondary mice for 30 d, all 6 control inoculations produced tumors, while tumor cells derived from resveratrol-treated mice only caused 1 tumor of 6 inoculations. Further studies by TEM (Transmission electron microscopy) analysis, GFP-LC3-II puncta formation assay and western blot for LC3-II, Beclin1 and Atg 7, showed that resveratrol induces autophagy in BCSCs. Moreover, resveratrol suppresses Wnt/β-catenin signaling pathway in BCSCs; over-expression of β-catenin by transfecting the plasmid markedly reduced resveratrol-induced cytotoxicity and autophagy in BCSCs. Our findings indicated that resveratrol inhibits BCSCs and induces autophagy via suppressing Wnt/β-catenin signaling pathway.

Expression of miR-34c induces G2/M cell cycle arrest in breast cancer cells

Background

MicroRNA-34 is a family of three miRNAs that have been reported to function as tumor suppressor miRNAs and show decreased expression in various cancers. Here, we examine functions of miR-34c in basal-like breast cancer cells.

Methods

Data from The Cancer Genome Atlas (TCGA) were used for evaluation of expression in primary breast cancers. Cellular processes affected by miR-34c were investigated by thymidine incorporation, Annexin V-assays and cell cycle analysis using breast cancer cell lines. Effects on potential targets were analyzed with qPCR and Western blot.

Results

TCGA data revealed that miR-34c was expressed at lower levels in basal-like breast cancer tumors and low expression was associated with poor prognosis. Ectopic expression of miR-34c in basal-like breast cancer cell lines resulted in suppressed proliferation and increased cell death. Additionally, miR-34c influenced the cell cycle mainly by inducing an arrest in the G2/M phase. We found that expression levels of the known cell cycle-regulating miR-34 targets CCND1, CDK4 and CDK6, were downregulated upon miR-34c expression in breast cancer cell lines. In addition, the levels of CDC23, an important mediator in mitotic progression, were suppressed following miR-34c expression, and siRNAs targeting CDC23 mimicked the effect of miR-34c on G2/M arrest. However, protein levels of PRKCA, a predicted miR-34c target and a known regulator of breast cancer cell proliferation were not influenced by miR-34c.

Conclusions

Together, our results support the role of miR-34c as a tumor suppressor miRNA also in breast cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-538) contains supplementary material, which is available to authorized users.

Downregulation of PEBP4, a target of miR-34a, sensitizes drug-resistant lung cancer cells

The aim of this study was to determine the relationship and underlying mechanisms between ectopic expression of phosphatidylethanolamine-binding protein 4 (PEBP4) and cisplatin (DDP)-induced cytotoxicity in the lung cancer cell line A549 to provide an experimental basis for future chemotherapeutic applications involving PEBP4 in human lung cancer. A recombinant plasmid, pcDNA3-PEBP4, and a PEBP4-targeting small hairpin RNA (shRNA) were transfected into the lung cancer cell line A549. The PEBP4 protein expression levels were determined for each group by Western blot, and after 48 h of cisplatin (DDP) treatment, the viability of cells in the treatment and control groups was determined by 3-[4,5-dimethylthiazol-2-yl]-3,5-diphenyltetrazolium bromide (MTT) assay. Apoptosis in each treatment group was determined using flow cytometry. Western blotting was used to examine expression of the p53 protein in A549 cells from each group. We employed a luciferase reporter-gene assay to confirm PEBP4 as a target gene of miR-34a. Western blotting was used to determine the effects of miR-34a on PEBP4 protein expression in A549 cells. Following transfection of A549 cells with either the recombinant plasmid pcDNA3-PEBP4 or a PEBP4-targeting shRNA, Western blotting analyses showed PEBP4 protein expression was significantly higher in the pcDNA3-PEBP4-transfected group compared with the control or PEBP4-shRNA-transfected groups (p < 0.01). Furthermore, PEBP4 protein expression was significantly reduced in the PEBP4-shRNA-transfected group (p < 0.01). After 48 h of DDP treatment, MTT assays indicated that A549 cell viability was significantly lower in the DDP-treated group compared with the control group (p < 0.01). The viability of A549 cells in the pcDNA3-PEBP4-transfected group was lower than that in the control group (p < 0.05) but higher than that in either the DDP-treated or PEBP4-shRNA-transfected groups (p < 0.05). Moreover, the viability of A549 cells in the PEBP4-shRNA-transfected group was significantly lower than that in either the control (p < 0.01) or DDP-treated (p < 0.05) groups. Flow cytometry and Western blotting analyses indicated that the number of apoptotic cells and p53 protein expression were significantly higher in the DDP-treated group compared with the control group (p < 0.01). In the pcDNA3-PEBP4-transfected group, the number of apoptotic cells and p53 protein expression level were higher than those in the control group (p < 0.05) but lower than those in the DDP-treated and PEBP4-shRNA-transfected groups (p < 0.05). The number of apoptotic cells and p53 protein expression level in the PEBP4-shRNA-transfected group were higher than those in the control (p < 0.01) and DDP-treated (p < 0.05) groups. The luciferase reporter-gene assay showed that the relative luciferase activity after transfection with a miR-34a mimic was significantly reduced compared with the control group (p < 0.01). Western blotting analysis demonstrated that PEBP4 protein expression was significantly decreased in A549 cells 48 h after transfection with a miR-34a mimic compared with the control group (p < 0.01). In conclusion, overexpression of PEBP4 reduced the sensitivity of A549 cells to DDP-induced cytotoxicity, mainly through the altered expression of the p53 protein or the modulation of miR-34a.

Flavonoids, flavonoid subclasses and breast cancer risk: a meta-analysis of epidemiologic studies

Background

Studies have suggested the chemopreventive effects of flavonoids on carcinogenesis. Yet numbers of epidemiologic studies assessing dietary flavonoids and breast cancer risk have yielded inconsistent results. The association between flavonoids, flavonoid subclasses (flavonols, flavan-3-ols, etc.) and the risk of breast cancer lacks systematic analysis.

Objective

We aimed to examine the association between flavonoids, each flavonoid subclass (except isoflavones) and the risk of breast cancer by conducting a meta-analysis.

Design

We searched for all relevant studies with a prospective cohort or case-control study design published before July 1^st, 2012, using Cochrane library, MEDLINE, EMBASE and PUBMED. Summary relative risks (RR) were calculated using fixed- or random-effects models. All analyses were performed using STATA version 10.0.

Results

Twelve studies were included, involving 9 513 cases and 181 906 controls, six of which were prospective cohort studies, and six were case-control studies. We calculated the summary RRs of breast cancer risk for the highest vs lowest categories of each flavonoid subclass respectively. The risk of breast cancer significantly decreased in women with high intake of flavonols (RR = 0.88, 95% CI 0.80–0.98) and flavones (RR = 0.83, 95% CI: 0.76–0.91) compared with that in those with low intake of flavonols and flavones. However, no significant association of flavan-3-ols (RR = 0.93, 95% CI: 0.84–1.02), flavanones (summary RR = 0.95, 95% CI: 0.88–1.03), anthocyanins (summary RR = 0.97, 95% CI: 0.87–1.08) or total flavonoids (summary RR = 0.98, 95% CI: 0.86–1.12) intake with breast cancer risk was observed. Furthermore, summary RRs of 3 case-control studies stratified by menopausal status suggested flavonols, flavones or flavan-3-ols intake is associated with a significant reduced risk of breast cancer in post-menopausal while not in pre-menopausal women.

Conclusions

The present study suggests the intake of flavonols and flavones, but not other flavonoid subclasses or total flavonoids, is associated with a decreased risk of breast cancer, especially among post-menopausal women.