MicroRNA-21 links epithelial-to-mesenchymal transition and inflammatory signals to confer resistance to neoadjuvant trastuzumab and chemotherapy in HER2-positive breast cancer patients

Role of miR-21 as an authentic oncogene in mediating drug resistance in breast cancer

Breast cancer (BC) is the most common cancer among women that is responsible for the most of the cancer-related death in worldwide. Drug resistance is remaining as a significant clinical obstacle to treat BC patients effectively. Therefore, to help overcome this problem, it is necessary to understand the mechanisms of drug resistance. microRNAs classify as highly conserved non-coding RNAs (~22 nucleotides) and interact with mRNAs-coding genes for direct post-transcriptional repression. It has been reported that miR-21 is overexpressed and also acts as oncomiR in many human malignancies by targeting of several tumor suppressor genes-associated with apoptosis, proliferation and metastasis. Specifically, it has been reported that miR-21 is responsible for the drug resistance and its overexpression is related to the development of Multi Drug Resistance (MDR) in breast cancer. In this review, we discussed about the role of miR-21 on the drug resistance of breast cancer.

Role of JAK/STAT3 Signaling in the Regulation of Metastasis, the Transition of Cancer Stem Cells, and Chemoresistance of Cancer by Epithelial-Mesenchymal Transition

The JAK/STAT3 signaling pathway plays an essential role in various types of cancers. Activation of this pathway leads to increased tumorigenic and metastatic ability, the transition of cancer stem cells (CSCs), and chemoresistance in cancer via enhancing the epithelial–mesenchymal transition (EMT). EMT acts as a critical regulator in the progression of cancer and is involved in regulating invasion, spread, and survival. Furthermore, accumulating evidence indicates the failure of conventional therapies due to the acquisition of CSC properties. In this review, we summarize the effects of JAK/STAT3 activation on EMT and the generation of CSCs. Moreover, we discuss cutting-edge data on the link between EMT and CSCs in the tumor microenvironment that involves a previously unknown function of miRNAs, and also discuss new regulators of the JAK/STAT3 signaling pathway.

Advances in the discovery of microRNA-based anticancer therapeutics: latest tools and developments

Introduction: MicroRNAs (miRNAs) are small endogenous non-coding RNAs that repress the expression of their target genes by reducing mRNA stability and/or inhibiting translation. miRNAs are known to be aberrantly regulated in cancers. Modulators of miRNA (mimics and antagonists) have emerged as novel therapeutic tools for cancer treatment.Areas covered: This review summarizes the various strategies that have been applied to correct the dysregulated miRNA in cancer cells. The authors also discuss the recent advances in the technical development and preclinical/clinical evaluation of miRNA-based therapeutic agents.Expert opinion: Application of miRNA-based therapeutics for cancer treatment is appealing because they are able to modulate multiple dysregulated genes and/or signaling pathways in cancer cells. Major obstacles hindering their clinical development include drug delivery, off-target effects, efficacious dose determination, and safety. Tumor site-specific delivery of novel miRNA therapeutics may help to minimize off-target effects and toxicity. Combination of miRNA therapeutics with other anticancer treatment modalities could provide a synergistic effect, thus allowing the use of lower dose, minimizing off-target effects, and improving the overall safety profile in cancer patients. It is critical to identify individual miRNAs with cancer type-specific and context-specific regulation of oncogenes and tumor-suppressor genes in order to facilitate the precise use of miRNA anticancer therapeutics.

MicroRNAs Involved in Carcinogenesis, Prognosis, Therapeutic Resistance and Applications in Human Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is the most aggressive, prevalent, and distinct subtype of breast cancer characterized by high recurrence rates and poor clinical prognosis, devoid of both predictive markers and potential therapeutic targets. MicroRNAs (miRNA/miR) are a family of small, endogenous, non-coding, single-stranded regulatory RNAs that bind to the 3′-untranslated region (3′-UTR) complementary sequences and downregulate the translation of target mRNAs as post-transcriptional regulators. Dysregulation miRNAs are involved in broad spectrum cellular processes of TNBC, exerting their function as oncogenes or tumor suppressors depending on their cellular target involved in tumor initiation, promotion, malignant conversion, and metastasis. In this review, we emphasize on masses of miRNAs that act as oncogenes or tumor suppressors involved in epithelial–mesenchymal transition (EMT), maintenance of stemness, tumor invasion and metastasis, cell proliferation, and apoptosis. We also discuss miRNAs as the targets or as the regulators of dysregulation epigenetic modulation in the carcinogenesis process of TNBC. Furthermore, we show that miRNAs used as potential classification, prognostic, chemotherapy and radiotherapy resistance markers in TNBC. Finally, we present the perspective on miRNA therapeutics with mimics or antagonists, and focus on the challenges of miRNA therapy. This study offers an insight into the role of miRNA in pathology progression of TNBC.

Improving the therapeutic efficiency of noncoding RNAs in cancers using targeted drug delivery systems

The delivery of noncoding (nc)RNA to target cancer stem cells and metastatic tumors has shown many positive outcomes, resulting in improved and more efficient treatment strategies. The success of therapeutic RNA depends solely on passing cellular barriers to reach the target site, where it binds to the mRNA of the interest. By 2018, 20 clinical trials had been initiated, most focusing on cancer and diabetes, with some progressing to Phase II clinical trials testing the safety and efficacy of small interfering (si)RNA. Many challenges limit RNA interference (RNAi) and miRNA usage in vivo; therefore, various approaches have been developed to promote ncRNA efficiency and stability. In this review, we focus on targeting the tumor microenvironment (TME) via the modification of delivery systems utilizing nanotechnology-based delivery approaches.

FOXC1 Regulation of miR-31-5p Confers Oxaliplatin Resistance by Targeting LATS2 in Colorectal Cancer

Colorectal cancer (CRC) is the second leading cause of cancer-related illness worldwide and one of the most common malignancies. Therefore, colorectal cancer research and cases have gained increasing attention. Oxaliplatin (OXA) is currently used in first-line chemotherapy to treat stage III and stage IV metastatic CRC. However, patients undergoing chemotherapy often develop resistance to chemo drugs being used. Evidence has confirmed that microRNAs regulate downstream genes in cancer biology and thereby have roles related to tumor growth, proliferation, invasion, angiogenesis, and multi-drug resistance. The aim of our study is to establish whether miR-31-5p is an oncogene in human colorectal cancers that are resistant to OXA and further confirm its malignant phenotype-associated target molecule. From the results of miRNA microarray assay, we establish that miR-31-5p expression was upregulated in oxaliplatin-resistant (OR)-LoVo cells compared with parental LoVo cells. Moreover, through in vitro and in vivo experiments, we demonstrate that miR-31-5p and large tumor suppressor kinase 2 (LATS2) were inversely related and that miR-31-5p and Forkhead box C1 (FOXC1) were positively correlated in the same LoVo or OR-LoVo cells. Importantly, we reveal a novel drug-resistance mechanism in which the transcription factor FOXC1 binds to the miR-31 promoter to increase the expression of miR31-5p and regulate LATS2 expression, resulting in cancer cell resistance to OXA. These results suggest that miR-31-5p may be a novel biomarker involved in drug resistance progression in CRC patients. Moreover, the FOXC1/miR31-5p/LATS2 drug-resistance mechanism provides new treatment strategies for CRC in clinical trials.

Clinical Theragnostic Relationship between Drug-Resistance Specific miRNA Expressions, Chemotherapeutic Resistance, and Sensitivity in Breast Cancer: A Systematic Review and Meta-Analysis

Awareness of breast cancer has been increasing due to early detection, but the advanced disease has limited treatment options. There has been growing evidence on the role of miRNAs involved in regulating the resistance in several cancers. We performed a comprehensive systematic review and meta-analysis on the role of miRNAs in influencing the chemoresistance and sensitivity of breast cancer. A bibliographic search was performed in PubMed and Science Direct based on the search strategy, and studies published until December 2018 were retrieved. The eligible studies were included based on the selection criteria, and a detailed systematic review and meta-analysis were performed based on PRISMA guidelines. A random-effects model was utilised to evaluate the combined effect size of the obtained hazard ratio and 95% confidence intervals from the eligible studies. Publication bias was assessed with Cochran’s Q test, I² statistic, Orwin and Classic fail-safe N test, Begg and Mazumdar rank correlation test, Duval and Tweedie trim and fill calculation and the Egger’s bias indicator. A total of 4584 potential studies were screened. Of these, 85 articles were eligible for our systematic review and meta-analysis. In the 85 studies, 188 different miRNAs were studied, of which 96 were upregulated, 87 were downregulated and 5 were not involved in regulation. Overall, 24 drugs were used for treatment, with doxorubicin being prominently reported in 15 studies followed by Paclitaxel in 11 studies, and 5 drugs were used in combinations. We found only two significant HR values from the studies (miR-125b and miR-4443) and our meta-analysis results yielded a combined HR value of 0.748 with a 95% confidence interval of 0.508–1.100; p-value of 0.140. In conclusion, our results suggest there are different miRNAs involved in the regulation of chemoresistance through diverse drug genetic targets. These biomarkers play a crucial role in guiding the effective diagnostic and prognostic efficiency of breast cancer. The screening of miRNAs as a theragnostic biomarker must be brought into regular practice for all diseases. We anticipate that our study serves as a reference in framing future studies and clinical trials for utilising miRNAs and their respective drug targets.

Serum microRNA-21 predicted treatment outcome and survival in HER2-positive breast cancer patients receiving neoadjuvant chemotherapy combined with trastuzumab

PURPOSE

The purpose of this study was to evaluate the expression of ser-miRNAs at different periods during treatment and analyze their relationship with therapeutic response and prognosis in HER2-positive breast cancer patients receiving neoadjuvant chemotherapy combined with trastuzumab (NCCT).

METHODS

Venous blood was drawn from patients at different periods during NCCT. The expression of ser-miRNAs was assessed by qRT-PCR and their relation to treatment response and survival was analyzed.

RESULTS

The results showed the expression of miR-10b, -21, -34a, -125b, -145, -155, and -373 in patients before the start of treatment was significantly higher, ser-miR-210 was lower, and ser-miR-122 was comparable to the levels in healthy controls. Changes in ser-miR-21 levels during NCCT were significantly correlated to clinical response and survival and, however, were not associated with pathology response. The expression levels of ser-miR-21 were decreased from the start of NCCT to the end of the second cycle and from the start to the end of NCCT in clinical responders; however, there was no significant difference in non-responders. The patients with decreased ser-miR-21 expression from the start to the end of the second cycle and from the start to the end of NCCT had better overall survival (OS) and disease-free survival (DFS) than those with elevated ser-miR-21 expression.

CONCLUSION

These results showed that changes in ser-miR-21 levels were significantly related to NCCT clinical response and prognosis. Ser-miR-21 may serve as a non-invasive biomarker to predict NCCT response in HER2-positive breast cancer.

Expression pattern of microRNAs related with response to trastuzumab in breast cancer

BACKGROUND

Although an immense effort has been made to develop a novel biomarker for response to trastuzumab, no reliable biomarkers are available to guide management, expect for HER2. The aim of this study was to examine the relationship between microRNA (miRNA) expression and resistance to trastuzumab.

METHODS

Differentially expressed miRNAs between trastuzumab-resistant and trastuzumab-sensitive cell lines were analyzed using microarrays. We performed Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses to determine the functions of differentially expressed miRNA and their targeted genes. Furthermore, the protein-protein interactions (PPI) network was analyzed. Serum samples were collected from patients with HER2-positive breast cancer who were treated with trastuzumab. We validated the miRNAs expression levels by quantitative reverse-transcription polymerase chain reaction (qRT-PCR) in these serums. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the predictive performance of the miRNA.

RESULTS

Using miRNA microarrays, 151 miRNAs that significant differentially expressed between the trastuzumab-resistant and sensitive cells were identified, including 46 upregulated and 105 downregulated miRNAs. Results of real-time PCR confirmed seven miRNAs in cell lines. PI3K-Akt signaling pathway was involved in regulating biological function according to KEGG analysis. Compared with the serums of trastuzumab-sensitive patients, three miRNAs, namely miR-200b, miR-135b, and miR-29a, were identified to be upregulated, and miR-224 was downregulated in the trastuzumab-resistant serums. ROC analysis showed that four miRNAs were correlated with trastuzumab resistance. Furthermore, three subnetwork modules of PPI network were obtained.

CONCLUSION

The results indicated that miRNAs were reliable predictive biomarkers for response to trastuzumab.

11PS04 is a new chemical entity identified by microRNA-based biosensing with promising therapeutic potential against cancer stem cells

Phenotypic drug discovery must take advantage of the large amount of clinical data currently available. In this sense, the impact of microRNAs (miRs) on human disease and clinical therapeutic responses is becoming increasingly well documented. Accordingly, it might be possible to use miR-based signatures as phenotypic read-outs of pathological status, for example in cancer. Here, we propose to use the information accumulating regarding the biology of miRs from clinical research in the preclinical arena, adapting it to the use of miR biosensors in the earliest steps of drug screening. Thus, we have used an amperometric dual magnetosensor capable of monitoring a miR-21/miR-205 signature to screen for new drugs that restore these miRs to non-tumorigenic levels in cell models of breast cancer and glioblastoma. In this way we have been able to identify a new chemical entity, 11PS04 ((3aR,7aS)-2-(3-propoxyphenyl)-7,7a-dihydro-3aH-pyrano[3,4-d]oxazol-6(4H)-one), the therapeutic potential of which was suggested in mechanistic assays of disease models, including 3D cell culture (oncospheres) and xenografts. These assays highlighted the potential of this compound to attack cancer stem cells, reducing the growth of breast and glioblastoma tumors in vivo. These data demonstrate the enhanced chain of translatability of this strategy, opening up new perspectives for drug-discovery pipelines and highlighting the potential of miR-based electro-analytical sensors as efficient tools in modern drug discovery.

Mechanisms behind prometastatic changes induced by neoadjuvant chemotherapy in the breast cancer microenvironment

Chemotherapy, along with surgery and radiotherapy, is a key treatment option for malignant tumors. Neoadjuvant chemotherapy (NACT) reduces the tumor size and enables total tumor resection. In addition, NACT is believed to be more effective in destroying micrometastases than the same chemotherapy performed after surgery. To date, various NACT regimens have been tested and implemented, which provide a favorable outcome in primary tumors and reduce the risk of progression. However, there is increasing evidence of the NACT ability to increase the risk of cancer progression. This review discusses potential mechanisms by which NACT promotes distant metastasis of breast cancer through changes in the microenvironment of tumor cells. We describe prometastatic NACT-mediated changes in angiogenesis, immuno-inflammatory reactions in the stroma, intravasation, and amount of circulating tumor cells. The role of NACT-related cellular stress in cancer metastasis is also discussed.

Emerging targets in cancer drug resistance

Drug resistance is a complex phenomenon that frequently develops as a failure to chemotherapy during cancer treatment. Malignant cells increasingly generate resistance to various chemotherapeutic drugs through distinct mechanisms and pathways. Understanding the molecular mechanisms involved in drug resistance remains an important area of research for identification of precise targets and drug discovery to improve therapeutic outcomes. This review highlights the role of some recent emerging targets and pathways which play critical role in driving drug resistance.

Gene Expression and miRNAs Profiling: Function and Regulation in Human Epidermal Growth Factor Receptor 2 (HER2)-Positive Breast Cancer

Breast cancer is the second most common cause of cancer-related deaths among women worldwide. It is a heterogeneous disease with four major molecular subtypes. One of the subtypes, human epidermal growth factor receptor 2 (HER2)-enriched (HER2-positive) is characterized by the absence of estrogen and progesterone receptors and overexpression of HER2 receptor, and accounts for 15–20% of all breast cancers. Despite the anti-HER2 and cytotoxic chemotherapy, HER2 subtype is an aggressive disease with significant mortality. Recent advances in molecular biology techniques, including gene expression profiling, proteomics, and microRNA analysis, have been extensively used to explore the underlying mechanisms behind human breast carcinogenesis and metastasis including HER2-positive breast cancer, paving the way for developing new targeted therapies. This review focuses on recent advances on gene expression and miRNA status in HER2-positive breast cancer.

Chemotherapy and Inflammatory Cytokine Signalling in Cancer Cells and the Tumour Microenvironment

Cancer is the result of a cell's acquisition of a variety of biological capabilities or 'hallmarks' as outlined by Hanahan and Weinberg. These include sustained proliferative signalling, the ability to evade growth suppressors, resisting cell death, enabling replicative immortality, inducing angiogenesis, and the ability to invade other tissue and metastasize. More recently, the ability to escape immune destruction has been recognized as another important hallmark of tumours. It is suggested that genome instability and inflammation accelerates the acquisition of a variety of the above hallmarks. Inflammation, is a product of the body's response to tissue damage or pathogen invasion. It is required for tissue repair and host defense, but prolonged inflammation can often be the cause for disease. In a cancer patient, it is often unclear whether inflammation plays a protective or deleterious role in disease progression. Chemotherapy drugs can suppress tumour growth but also induce pathways in tumour cells that have been shown experimentally to support tumour progression or, in other cases, encourage an anti-tumour immune response. Thus, with the goal of better understanding the context under which each of these possible outcomes occurs, recent progress exploring chemotherapy-induced inflammatory cytokine production and the effects of cytokines on drug efficacy in the tumour microenvironment will be reviewed. The implications of chemotherapy on host and tumour cytokine pathways and their effect on the treatment of cancer patients will also be discussed.

Current Updates on Trastuzumab Resistance in HER2 Overexpressing Breast Cancers

Trastuzumab represents the predominant therapy to target breast cancer subtype marked by HER2 amplification. It has been in use for two decades and its continued importance is underlined by recent FDA approvals of its biosimilar and conjugated versions. Progression to an aggressive disease with acquisition of resistance to trastuzumab remains a major clinical concern. In addition to a number of cellular signaling pathways being investigated, focus in recent years has also shifted to epigenetic and non-coding RNA basis of acquired resistance against trastuzumab. This article provides a succinct discussion on the most recent advances in our understanding of such factors.

Potential Regulatory Roles of MicroRNAs and Long Noncoding RNAs in Anticancer Therapies

MicroRNAs and long noncoding RNAs have long been investigated due to their roles as diagnostic and prognostic biomarkers of cancers and regulators of tumorigenesis, and the potential regulatory roles of these molecules in anticancer therapies are attracting increasing interest as more in-depth studies are performed. The major clinical therapies for cancer include chemotherapy, immunotherapy, and targeted molecular therapy. MicroRNAs and long noncoding RNAs function through various mechanisms in these approaches, and the mechanisms involve direct targeting of immune checkpoints, cooperation with exosomes in the tumor microenvironment, and alteration of drug resistance through regulation of different signaling pathways. Herein we review the regulatory functions and significance of microRNAs and long noncoding RNAs in three anticancer therapies, especially in targeted molecular therapy, and their mechanisms.

CRISPR Technology for Breast Cancer: Diagnostics, Modeling, and Therapy

Molecularly, breast cancer represents a highly heterogenous family of neoplastic disorders, with substantial interpatient variations regarding genetic mutations, cell composition, transcriptional profiles, and treatment response. Consequently, there is an increasing demand for alternative diagnostic approaches aimed at the molecular annotation of the disease on a patient-by-patient basis and the design of more personalized treatments. The clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated (Cas) technology enables the development of such novel approaches. For instance, in diagnostics, the use of the RNA-specific C2c2 system allows ultrasensitive nucleic acid detection and could be used to characterize the mutational repertoire and transcriptional breast cancer signatures. In disease modeling, CRISPR/Cas9 technology can be applied to selectively engineer oncogenes and tumor-suppressor genes involved in disease pathogenesis. In treatment, CRISPR/Cas9 can be used to develop gene-therapy, while its catalytically-dead variant (dCas9) can be applied to reprogram the epigenetic landscape of malignant cells. As immunotherapy becomes increasingly prominent in cancer treatment, CRISPR/Cas9 can engineer the immune cells to redirect them against cancer cells and potentiate antitumor immune responses. In this review, CRISPR strategies for the advancement of breast cancer diagnostics, modeling, and treatment are highlighted, culminating in a perspective on developing a precision medicine-based approach against breast cancer.

miR-134 targets PDCD7 to reduce E-cadherin expression and enhance oral cancer progression

Oral squamous cell carcinoma (OSCC) is a common malignancy worldwide. This study clarified the oncogenic role of miR-134 in OSCC. Reporter assays, using both wild-type and mutant constructs, confirmed that Programmed Cell Death 7 (PDCD7) gene was a potential target of miR-134. The OSCC cells exogenously expressed miR-134 exhibited reduced PDCD7 expression. As expected, exogenous miRZip-134 expression increased PDCD7 expression in the OSCC cells; additionally, PDCD7 expression suppressed the oncogenicity of the OSCC cells. By contrast, PDCD7 knockout through gene editing increased in vitro oncogenicity and neck nodal metastasis in mice, and reduced E-cadherin (E-cad) expression. PDCD7 transactivated E-cad expression via the GC-box in the promoter. Moreover, miR-134-associated cellular transformation and E-cad downregulation was attenuated by PDCD7. Downregulation of both PDCD7 and E-cad and high levels miR-134 expression was observed in OSCC tumor tissues. Activation of the miR-134-PDCD7-E-cad pathogenesis cascade occurred early during the human and murine oral carcinogenesis process. In conclusion, the oncogenic effect of miR-134 in oral carcinoma is mediated by reducing PDCD7 and E-cad expression.

Molecular subtype predicts incidence and prognosis of brain metastasis from breast cancer in SEER database

PURPOSE

To evaluate the impact of molecular subtype on incidence and prognosis of brain metastasis from breast cancer.

METHODS

The Surveillance, Epidemiology, and End Results (SEER) 18 registry was used to select breast cancer patients from 2010 to 2014. Molecular subtypes were classified as luminal A (hormone receptor [HR]+/human epidermal growth factor receptor 2 [HER2]-), luminal B (HR+/HER2+), HER2 (HR-/HER2+), or triple negative breast cancer (TNBC) (HR-/HER2-). The incidence and prognosis of brain metastasis was evaluated according to molecular subtype.

RESULTS

Among the 206913 breast cancer patients, the HER2 subtype showed the highest incidence of brain metastasis (1.0%). HER2 and TNBC with multiple extracranial metastases (bone, liver, and lung) showed a high incidence of brain metastasis (28.0 and 30.8%, respectively). Median survival of luminal A, luminal B, HER2, and TNBC in brain metastasis was 12, 23, 10, and 6 months (p < 0.001), and in brain metastasis without visceral metastasis was 14, 34, 17, and 8 months (p < 0.001). On multivariate analysis, the order of subtype by favorable prognosis was luminal B, luminal A, HER2, and TNBC in all brain metastasis, while for brain metastasis patients without visceral metastasis, the order was luminal B, HER2, luminal A, and TNBC.

CONCLUSIONS

Molecular subtype and visceral metastasis should be considered for prediction of prognosis for patients with brain metastasis. The patients with HER2 and TNBC cancer subtypes having visceral metastasis, close surveillance could contribute to early detection of brain metastasis and may putatively lead to improved quality of life and survival.

MicroRNAs in cancer drug resistance: Basic evidence and clinical applications

Development of drug resistance has considerably limited the efficacy of cancer treatments, including chemotherapy and targeted therapies. Hence, understanding the molecular mechanisms underpinning the innate or the acquired resistance to these therapies is critical to improve drug efficiency and clinical outcomes. Several studies have implicated microRNAs (miRNA) in this process. MiRNAs repress gene expression by specific binding to complementary sequences in the 3' region of target messenger RNAs (mRNAs), followed by target mRNA degradation or blocked translation. By targeting molecules specific to a particular pathway within tumor cells, the new generation of cancer treatment strategies has shown significant advantages over conventional chemotherapy. However, the long-term efficacy of targeted therapies often remains poor, because tumor cells develop resistance to such therapeutics. Targeted therapies often involve monoclonal antibodies (mAbs), such as those blocking the ErB/HER tyrosine kinases, epidermal growth factor receptor (cetuximab) and HER2 (trastuzumab), and those inhibiting vascular endothelial growth factor receptor signaling (e.g., bevacizumab). Even though these are among the most used agents in tumor medicine, clinical response to these drugs is reduced due to the emergence of drug resistance as a result of toxic effects in the tumor microenvironment. Research on different types of human cancers has revealed that aberrant expression of miRNAs promotes resistance to the aforementioned drugs. In this study, we review the mechanisms of tumor cell resistance to mAb therapies and the role of miRNAs therein. Emerging treatment strategies combine therapies using innovative miRNA mimics or antagonizers with conventional approaches to maximize outcomes of patients with cancer.

Dynamic microRNA activity identifies therapeutic targets in trastuzumab-resistant HER2+ breast cancer

MicroRNAs (miRNAs) are implicated in numerous physiologic and pathologic processes, such as the development of resistance to chemotherapy. Determining the role of miRNAs in these processes is often accomplished through measuring miRNA abundance by polymerase chain reaction, sequencing, or microarrays. We have developed a system for the large-scale monitoring of dynamic miRNA activity and have applied this system to identify the contribution miRNA activity to the development of trastuzumab resistance in a cell model of HER2⁺ breast cancer. MiRNA activity measurements identified significantly different activity levels between BT474 cells (HER2 ⁺ breast cancer) and BT474R cells (HER2 ⁺ breast cancer cells selected for resistance to trastuzumab). We created a library of 32 miRNA reporter constructs, which were delivered by lentiviral transduction into cells, and miRNA activity was quantified by bioluminescence imaging. Upon treatment with the bioimmune therapy, trastuzumab, the activity of 11 miRNAs were significantly altered in parental BT474 cells, and 20 miRNAs had significantly altered activity in the therapy-resistant BT474R cell line. A combination of statistical, network and classification analysis was applied to the dynamic data, which identified miR-21 as a controlling factor in trastuzumab response. Our data suggested downregulation of miR-21 activity was associated with resistance, which was confirmed in an additional HER2 ⁺ breast cancer cell line, SKBR3. Collectively, the dynamic miRNA activity measurements and analysis provided a system to identify new potential therapeutic targets in treatment-resistant cancers.

MicroRNAs in regulation of triple-negative breast cancer progression

PURPOSE

Dysregulation of miRNA profile has been associated with a broad spectrum of cellular processes underlying progression of various human malignancies. Increasing evidence suggests that specific microRNA clusters might be of clinical utility, especially in triple-negative breast carcinoma (TNBC), devoid of both predictive markers and potential therapeutic targets. Here we provide a comprehensive review of the existing data on microRNAs in TNBC, their molecular targets, a putative role in invasive progression with a particular emphasis on the epithelial-to-mesenchymal transition (EMT) and acquisition of stem-cell properties (CSC), regarded both as prerequisites for metastasis, and significance for therapy.

METHODS

PubMed and Medline databases were systematically searched for the relevant literature. 121 articles have been selected and thoroughly analysed.

RESULTS

Several miRNAs associated with EMT/CSC and invasion were identified as significantly (1) upregulated: miR-10b, miR-21, miR-29, miR-9, miR-221/222, miR-373 or (2) downregulated: miR-145, miR-199a-5p, miR-200 family, miR-203, miR-205 in TNBC. Dysregulation of miR-10b, miR-21, miR-29, miR-145, miR-200 family, miR-203, miR-221/222 was reported of prognostic value in TNBC patients.

CONCLUSION

Available data suggest that specific microRNA clusters might play an important role in biology of TNBC, understanding of which should assist disease prognostication and therapy.

miRNA-199a-5p suppresses proliferation and invasion by directly targeting NF-κB1 in human ovarian cancer cells

The aberrant expression of microRNA (miRNA)-199a-5p has been frequently reported in a number of cancer types, but to the best of our knowledge, this has not been reported in ovarian cancer (OC). The role and the molecular mechanism of miR-199a-5p in OC have not been reported. Therefore, the present study investigated the effects of miR-199a-5p overexpression on the proliferation and invasion of OC cells. The level of miR-199a-5p in OC cell lines was determined by reverse transcription-quantitative polymerase chain reaction. The miR-199a-5p mimic was transiently transfected into OC cells using Lipofectamine^™ 2000 reagent. Subsequently, the BrdU-ELISA results indicated that the exogenous expression of miR-199a-5p inhibited cell proliferation. In addition, miR-199a-5p overexpression was able to inhibit the invasion of HO-8910 and ES-2 cells. RT-qPCR was performed to determine the expression of matrix metalloproteinase (MMP)-2 and -9 in OC cells. NF-κB1 expression was reduced by upregulation of miR-199a-5p. Bioinformatics analysis predicted that NF-κB1 was a potential target of miR-199a-5p. Luciferase reporter assay further confirmed that miR-199a-5p was able to directly target the 3'UTR of NF-κB1. In conclusion, miRNA-199a-5p may suppress the proliferation and invasion of human ovarian cancer cells by directly targeting NF-κB1.

HER2 inhibition in gastro-oesophageal cancer: A review drawing on lessons learned from breast cancer

Human epidermal growth factor receptor 2 (HER2)-inhibition is an important therapeutic strategy in HER2-amplified gastro-oesophageal cancer (GOC). A significant proportion of GOC patients display HER2 amplification, yet HER2 inhibition in these patients has not displayed the success seen in HER2 amplified breast cancer. Much of the current evidence surrounding HER2 has been obtained from studies in breast cancer, and we are only recently beginning to improve our understanding of HER2-amplified GOC. Whilst there are numerous licensed HER2 inhibitors in breast cancer, trastuzumab remains the only licensed HER2 inhibitor for HER2-amplified GOC. Clinical trials investigating lapatinib, trastuzumab emtansine, pertuzumab and MM-111 in GOC have demonstrated disappointing results and have not yet changed the treatment paradigm. Trastuzumab deruxtecan may hold promise and is currently being investigated in phase II trials. HER2 amplified GOC differs from breast cancer due to inherent differences in the HER2 amino-truncation and mutation rate, loss of HER2 expression, alterations in HER2 signalling pathways and differences in insulin-like growth factor-1 receptor and MET expression. Epigenetic alterations involving different microRNA profiles in GOC as compared to breast cancer and intrinsic differences in the immune environment are likely to play a role. The key to effective treatment of HER2 amplified GOC lies in understanding these mechanisms and tailoring HER2 inhibition for GOC patients in order to improve clinical outcomes.

Cancer stem cells in triple-negative breast cancer: a potential target and prognostic marker

Triple-negative breast cancer (TNBC) is an aggressive disease with poor outcome, and lacks targeted therapy. Recent studies suggest that cancer stem cells play an important role in tumorigenesis and tumor biology of TNBC. Both CD44+/CD24- and ALDH1+ breast cancer stem cells are enriched in TNBC and may contribute to the propensity of TNBC for chemotherapy resistance and tumor metastasis. There is new evidence to support the evaluation of cancer stem cells in TNBC for diagnostic purposes. Targeting cancer stem cells may also be a promising, novel strategy for the treatment of TNBC. This review highlights the current understanding of breast cancer stem cells in TNBC, with focus on CD44+/CD24- and ALDH1+ breast cancer stem cells. It is our hope that this work provides insight into the potential role of cancer stem cells in the prognostication and therapeutic targeting of TNBC.

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.

MiR-205 as predictive biomarker and adjuvant therapeutic tool in combination with trastuzumab

Trastuzumab is the standard treatment for HER2+ breast cancer (BC) patients, and even though it significantly improved their clinical outcome, 50% of them do not benefit from this drug and disease recurs, underlining the need of reliable predictive biomarkers and new therapeutic strategies. Strikingly, despite all the molecular analyses performed to identify the escape mechanisms behind this resistance, it still represents a question point. MiRNAs have been correlated with occurrence and progression of human cancer, and their potential as clinical tools has emerged in the last years. We previously reported that oncosuppressive miR-205 targets HER3, thus increasing the responsiveness to TKIs lapatinib and gefitinib in preclinical models.

Here we demonstrate that HER3 inhibition by miR-205 ectopic expression or siRNA-mediated silencing improves the responsiveness to Trastuzumab in vitro in HER2+ BC cell lines, and that this effect is exerted through impairment of AKT-mediated pathway. Moreover, evaluating a series of 52 HER2+ BC patients treated with adjuvant Trastuzumab, we observed that higher miR-205 expression is significantly associated with better outcome (disease-free survival).

In summary, our data indicate that miR-205 could predict Trastuzumab efficacy and that its modulation might be useful as adjuvant treatment to improve the response to the drug.

MiR-21 improves invasion and migration of drug-resistant lung adenocarcinoma cancer cell and transformation of EMT through targeting HBP1

This study was aimed at the investigation of the effects of miR-21 on drug resistance, invasion, migration, and epithelial-mesenchymal transition (EMT) of lung adenocarcinoma cells and the related molecular mechanisms. Cell viability of A549 cell line was measured by MTT assay. Wound healing assay and transwell assay were, respectively, employed to examine cell migration and invasion abilities. The cells were transfected with miR-21 mimic or inhibitor using Lipofectamine 3000. The target relationship between miR-21 and HBP1 was confirmed by luciferase reporter gene assay. Western blot and qRT-PCR were used to examine the expression of HBP1 and EMT-related molecules. Compared with A549 cells, drug resistance of A549/PTX cells and A549/DDP cells were obviously stronger. A549/PTX cells and A549/DDP cells had stronger ability of migration and invasion compared with parental A549 cells. Meanwhile, EMT of A549/PTX and A549/DDP was significantly higher than that of A549 cells. MiR-21 promoted migration, invasion, and EMT of human lung adenocarcinoma cancer cells. Our experiment also verified the target relationship between miR-21 and HBP1. MiR-21 may affect migration and invasion ability of drug-resistant lung adenocarcinoma cells by targeting HBP1, therefore modulating EMT.

MiR-150-3p targets SP1 and suppresses the growth of glioma cells

Glioma has been considered as one of the most prevalent and common malignancy of the nervous system; however, the underlying mechanisms that are responsible for the occurrence and development of glioma still remain largely unknown. Amounting evidence highlights the critical regulatory function of miRNAs in carcinogenesis. Here, we showed that the expression of miR-150-3p was significantly decreased in glioma tissues and cell lines. Suppressed expression of miR-150-3p was associated with the lymph node metastasis of the glioma patients. Overexpression of miR-150-3p significantly inhibited the proliferation of glioma cells. Molecular study uncovered that the transcription factor specificity protein 1 (SP1) was identified as one of the targets of miR-150-3p Highly expressed miR-150-3p in glioma cells significantly decreased both the mRNA and protein levels of SP1. Consistently, the abundance of phosphatase and tension homolog deleted on chromosome ten (PTEN), a negative downstream target of SP1, was increased with the ectopic miR-150-3p Collectively, these results suggested that miR-150-3p suppressed the growth of glioma cells partially via regulating SP1 and possibly PTEN.

The HER4-YAP1 axis promotes trastuzumab resistance in HER2-positive gastric cancer by inducing epithelial and mesenchymal transition

Trastuzumab is the only target to be approved as the first-line treatment of HER2 positive metastatic gastric cancer, but ubiquitous resistance decreases its therapeutic benefit. In this study, we found HER4, phosphorylation HER4 (p-HER4) and the mesenchymal marker Vimentin increased in trastuzumab-resistant cells (MKN45TR and NCI-N87TR), while epithelial markers expressions in trastuzumab-resistant cell lines and animal models decreased. Additionally, silencing HER4 prevented the epithelial-mesenchymal transition and led to decreased proliferation and migration in vitro and in vivo. The expression of YAP1, a vital downstream interacted target of HER4, decreased when HER4 was knocked down. Interestingly, stimulation of NRG1 could compromise the inhibitory impact and rescue cell survival; whereas, transfection of siYAP1 sensitized trastuzumab-treated cells. Expression analysis of the proteins in patient-derived xenograft model (PDX) mice showed that HER4, p-HER4, YAP1, and Vimentin were clearly upregulated in the trastuzumab-resistant mice compared to mice without trastuzumab resistance. However, HER2 and E-cadherin were downregulated in response to continuous treatment with trastuzumab. These findings elucidated that the central role of the HER4-YAP1 axis in trastuzumab resistance of HER2-positive gastric cancer cells through induction of EMT. Hence, regulating the HER4-YAP1 axis might be a promising strategy for clinical interventions in patients with HER2-positive gastric cancer.

MiR-21 over-expression and Programmed Cell Death 4 down-regulation features malignant pleural mesothelioma

Background

Differential diagnosis between malignant pleural mesothelioma (MPM) and benign mesothelial conditions is still challenging and there is a lack of useful markers. Programmed cell death 4 (PDCD4) is a well-known tumor suppressor gene in several cancers, its post-transcriptional activity is directly controlled by miR-21, whose over-expression has been recently reported in MPM compared to normal mesothelium. Aim of this study was to test this suppressor gene as a possible new marker of malignant transformation in mesothelial cells, as well as a new prognostic marker.

Methods

PDCD4 nuclear expression was assessed by immunohistochemistry (IHC) in 40 non-neoplastic pleural (NNP) and 40 MPM formalin-fixed and paraffin-embedded specimens. PDCD4 and miR-21 expressions were analyzed by qRT-PCR in all cases. In situ hybridization (ISH) of miR-21 was performed in 5 representative cases of both groups. The prognostic relevance of PDCD4 was assessed in a public available gene expression dataset.

Results

IHC showed that PDCD4 nuclear expression was significantly lower in MPM than in NNP. PDCD4 was down-regulated, whereas miR-21 was over-expressed in MPM cases compared to NNP ones. ISH detected miR-21 only in MPM specimens. Down-expression of PDCD4 was found significantly associated with short overall survival in publicly available data.

Conclusions

These findings highlighted a switch between PDCD4 and miR-21 expression in MPM. Further studies should assess the diagnostic reliability of these two markers for MPM in biopsy and effusion specimens.

Cytokine-mediated therapeutic resistance in breast cancer

Therapeutic resistance leading to tumor relapse is a major challenge in breast cancer (BCa) treatment. Numerous factors involved in multiple mechanisms promote the development of tumor chemo/radio-resistance. Cytokines/chemokines are important inflammatory factors and highly related to tumorigenesis, metastasis and tumors responses to treatment. A large number of studies have demonstrated that the network of cytokines activates multiple cell signaling pathways to promote tumor cell survival, proliferation, invasion, and migration. Particularly in BCa, cytokines-enhanced the epithelial-mesenchymal transition (EMT) process plays a pivotal role in the progression of metastatic phenotypes and resistance to the traditional chemo/radio-therapy. Virtually, therapeutic resistance is not entirely determined by tumor cell intrinsic characteristics but also dependent upon synchronized effects by numerous of local microenvironmental factors. Emerging evidence highlighted that exosomes secreted from various types of cells promote intercellular communication by transferring bioactive molecules including miRNAs and cytokines, suggesting that exosomes are essential for sustentation of tumor progression and therapeutic resistance within the tumor microenvironment. In this review, we discuss the mechanisms by which cytokines promote therapeutic resistance of BCa and suggest a potential approach for improving BCa therapeutics by inhibition of exosome function.

Functional miRNAs in breast cancer drug resistance

Owing to improved early surveillance and advanced therapy strategies, the current death rate due to breast cancer has decreased; nevertheless, drug resistance and relapse remain obstacles on the path to successful systematic treatment. Multiple mechanisms responsible for drug resistance have been elucidated, and miRNAs seem to play a major part in almost every aspect of cancer progression, including tumorigenesis, metastasis, and drug resistance. In recent years, exosomes have emerged as novel modes of intercellular signaling vehicles, initiating cell–cell communication through their fusion with target cell membranes, delivering functional molecules including miRNAs and proteins. This review particularly focuses on enumerating functional miRNAs involved in breast cancer drug resistance as well as their targets and related mechanisms. Subsequently, we discuss the prospects and challenges of miRNA function in drug resistance and highlight valuable approaches for the investigation of the role of exosomal miRNAs in breast cancer progression and drug resistance.

Single-Step Incubation Determination of miRNAs in Cancer Cells Using an Amperometric Biosensor Based on Competitive Hybridization onto Magnetic Beads

This work reports an amperometric biosensor for the determination of miRNA-21, a relevant oncogene. The methodology involves a competitive DNA-target miRNA hybridization assay performed on the surface of magnetic microbeads (MBs) and amperometric transduction at screen-printed carbon electrodes (SPCEs). The target miRNA competes with a synthetic fluorescein isothiocyanate (FITC)-modified miRNA with an identical sequence for hybridization with a biotinylated and complementary DNA probe (b-Cp) immobilized on the surface of streptavidin-modified MBs (b-Cp-MBs). Upon labeling, the FITC-modified miRNA attached to the MBs with horseradish peroxidase (HRP)-conjugated anti-FITC Fab fragments and magnetic capturing of the MBs onto the working electrode surface of SPCEs. The cathodic current measured at −0.20 V (versus the Ag pseudo-reference electrode) was demonstrated to be inversely proportional to the concentration of the target miRNA. This convenient biosensing method provided a linear range between 0.7 and 10.0 nM and a limit of detection (LOD) of 0.2 nM (5 fmol in 25 μL of sample) for the synthetic target miRNA without any amplification step. An acceptable selectivity towards single-base mismatched oligonucleotides, a high storage stability of the b-Cp-MBs, and usefulness for the accurate determination of miRNA-21 in raw total RNA (RNA_t) extracted from breast cancer cells (MCF-7) were demonstrated.

Exosomal microRNA-32-5p induces multidrug resistance in hepatocellular carcinoma via the PI3K/Akt pathway

BACKGROUND

Multidrug resistance is the main obstacle for hepatocellular carcinoma (HCC) treatment. miR-32-5p is involved in HCC progression but its function in multidrug resistance is still unclear. Here we aim to find out the function of miR-32-5p in inducing multidrug resistance and its underlying mechanisms of transforming sensitive cell to resistant cell.

METHODS

We detected the expression of miR-32-5p and PTEN in the multidrug-resistant cell line (Bel/5-FU) and the sensitive cell line (Bel7402), HCC and para-carcinoma liver tissues through real-time PCR. Dual-luciferase reporter assay verified PTEN is the target of miR-32-5p. Exosomes from sensitive and multidrug resistant cell line were obtained and confirmed through ultracentrifuge and Nano Analyzer. Gain- and loss-of-function experiments, rescue experiments, a PI3K/Akt pathway inhibitor, an exosome biogenesis inhibitor, and nude mice xenograft models were used to determine the underlying mechanisms of miR-32-5p and PTEN, as well as exosomal miR-32-5p in inducing multidrug resistance in vitro and in vivo.

RESULTS

miR-32-5p was significantly elevated but PTEN was reduced in Bel/5-FU. An inverse correlation between miR-32-5p and PTEN was confirmed in HCC cell lines and patients; moreover, high expression of miR-32-5p and low expression of PTEN were positively associated with poor prognosis. Over-expression of miR-32-5p activated the PI3K/Akt pathway by suppressing PTEN and induced multidrug resistance via exosomes through promoting angiogenesis and epithelial-mesenchymal transition (EMT).

CONCLUSIONS

Our study demonstrated that the multidrug-resistant cell, Bel/5-FU delivers miR-32-5p to sensitive cell, Bel7402 by exosomes and activates the PI3K/Akt pathway to further induce multidrug resistance by modulating angiogenesis and EMT.

Onco-miR-130 promotes cell proliferation and migration by targeting TGFβR2 in gastric cancer

MicroRNAs (miRNAs) have been proved to play crucial roles in tumorigenesis. TGFβ signal pathway abnormality is found in various cancers and correlates with tumor proliferation and metastasis. However, the mechanisms underlying the dys-regulation of TGFβR2 expression in GC have not been investigated yet. In this study, we found that the TGFβR2 protein was clearly repressed in tumor tissues, while miR-130 expression level was dramatically increased in GC tissues. Firefly luciferase activity assay revealed that miR-130 could directly bind to 3′UTR of TGFβR2 mRNA. Meanwhile, miR-130 mimics lead to the decreased TGFβR2 protein levels, while miR-130 inhibitors enhanced TGFβR2 expression in SGC7901 cells. Subsequent functional experiments showed that overexpressed miR-130 could promote proliferation and migration of SGC7901 cells. And siRNA-mediated TGFβR2 down-regulation could simulate the effects of miR-130 mimics on phenotypes of SGC7901 cells. Furthermore, there existed intense relationship between the expression level of miR-130 and epithelial-mesenchymal markers. Our results demonstrated that miR-130 was an oncogene by directly targeting TGFβR2 in GC.

PD-L1, inflammation, non-coding RNAs, and neuroblastoma: Immuno-oncology perspective

Neuroblastoma is the most common pediatric solid tumor of neural crest origin. The current treatment options for neuroblastoma produce severe side effects. Programmed death-ligand 1 (PD-L1), chronic inflammation, and non-coding RNAs are known to play a significant role in the pathogenesis of neuroblastoma. Cancer cells and the surrounding cells in the tumor microenvironment express PD-L1. Programmed death-1 (PD-1) is a co-receptor expressed predominantly by T cells. The binding of PD-1 to its ligands, PD-L1 or PD-L2, is vital for the physiologic regulation of the immune system. Chronic inflammation is involved in the recruitment of leukocytes, production of cytokines and chemokines that in turn, lead to survival, metastasis, and angiogenesis in neuroblastoma tumors. The miRNAs and long non-coding (lnc) RNAs have emerged as a novel class of non-coding RNAs that can regulate neuroblastoma associated cell-signaling pathways. The dysregulation of PD-1/PD-L1, inflammatory pathways, lncRNAs, and miRNAs have been reported in clinical and experimental samples of neuroblastoma. These signaling molecules are currently being evaluated for their potential as the biomarker and therapeutic targets in the management of neuroblastoma. A monoclonal antibody called dinutuximab (Unituxin) that attaches to a carbohydrate molecule GD2, on the surface of many neuroblastoma cells, is being used as an immunotherapy drug for neuroblastoma treatment. Atezolizumab (Tecentriq), an engineered monoclonal antibody against PD-L1, are currently in clinical trial for neuroblastoma patients. The lncRNA/miRNA-based therapeutics is being developed to deliver tumor suppressor lncRNAs/miRNAs or silencing of oncogenic lncRNAs/miRNAs. The focus of this review is to discuss the current knowledge on the immune checkpoint molecules, PD-1/PD-L1 signaling, inflammation, and non-coding RNAs in neuroblastoma.

Biomarker significance of plasma and tumor miR-21, miR-221, and miR-106a in osteosarcoma

Osteosarcoma is the most common malignant bone tumor in children and young adults. Despite the use of surgery and multi-agent chemotherapy, osteosarcoma patients who have a poor response to chemotherapy or develop relapses have a dismal outcome. Identification of biomarkers for active disease may help to monitor tumor burden, detect early relapses, and predict prognosis in these patients. In this study, we examined whether circulating miRNAs can be used as biomarkers in osteosarcoma patients. We performed genome-wide miRNA profiling on a discovery cohort of osteosarcoma and control plasma samples. A total of 56 miRNAs were upregulated and 164 miRNAs were downregulated in osteosarcoma samples when compared to control plasma samples. miR-21, miR-221 and miR-106a were selected for further validation based on their known biological importance. We showed that all three circulating miRNAs were expressed significantly higher in osteosarcoma samples than normal samples in an independent cohort obtained from the Children's Oncology Group. Furthermore, we demonstrated that miR-21 was expressed significantly higher in osteosarcoma tumors compared with normal bone controls. More importantly, lower expressions of miR-21 and miR-221, but not miR-106a, significantly correlated with a poor outcome. In conclusion, our results indicate that miR-21, miR-221 and miR-106a were elevated in the circulation of osteosarcoma patients, whereas tumor expressions of miR-21 and miR-221 are prognostically significant. Further investigation of these miRNAs may lead to a better prognostic method and potential miRNA therapeutics for osteosarcoma.

Interrelation of the Circulating and Tissue MicroRNA-21 with Tissue PDCD4 Expression and the Invasiveness of Iraqi Female Breast Tumors

The changes in the translational repression and variation in mRNA degradation induced by micro RNA are important aspects of tumorigenesis. The association of microRNA-21 with clinicopathologic features and expression of programed cell death 4 (PDCD4) in Iraqi female's with breast tumors has not been studied. MicroRNAs were extracted from a set of 60 breast tumor tissues and blood samples of females with breast cancer and benign breast lesions obtained after breast-reductive surgery, and only blood samples from 30 normal volunteers. These extracts were evaluated for miR-21 expression by quantitative RT-PCR. Analysis of PDCD4 protein expression was carried out as miR-21 target gene by immunohistochemical tests and correlating the results with patients' clinicopathological features. Significant overexpression of miRNA-21 was found in breast cancer group. The fold increase in the miR-21 gene expression was significantly higher in circulating exosomes and breast tissues of breast cancer patients as compared to other groups (P < 0.001). Overexpression of miR-21 was also significantly associated with the advanced tumor stage and histological grade. In breast cancer patients, PDCD4 protein expression was decreased to about 70% of the level in the control group. The delta Ct of exosomal and breast tissue miRNA-21 was negatively associated with PDCD4 expression. In conclusion, the translational repression of the PDCD4 induced by the high expression of miR-21 promotes breast cell transformation and development of breast tumor, and circulating miR-21 level could be applied to the screening panels for early detection of women breast cancer.

The Pattern of microRNA Binding Site Distribution

Micro-RNA (miRNA or miR) regulates at least 60% of the genes in the human genome through their target sites at mRNA 3'-untranslated regions (UTR), and defects in miRNA expression regulation and target sites are frequently observed in cancers. We report here a systematic analysis of the distribution of miRNA target sites. Using the evolutionarily conserved miRNA binding sites in the TargetScan database (release 7.1), we constructed a miRNA co-regulation network by connecting genes sharing common miRNA target sites. The network possesses characteristics of the ubiquitous small-world network. Non-hub genes in the network-those sharing miRNA target sites with small numbers of genes-tend to form small cliques with their neighboring genes, while hub genes exhibit high levels of promiscuousness in their neighboring genes. Additionally, miRNA target site distribution is extremely uneven. Among the miRNAs, the distribution concentrates on a small number of miRNAs, in that their target sites occur in an extraordinarily large number of genes, that is, they have large numbers of target genes. The distribution across the genes follows a similar pattern; the mRNAs of a small proportion of the genes contain extraordinarily large numbers of miRNA binding sites. Quantitatively, the patterns fit into the P_(K) ∝ K^-α relationship (P_(K): the number of miRNAs with K target genes or genes with K miRNA sites; α: a positive constant), the mathematical description of connection distribution among the nodes and a defining characteristic of the so-called scale-free networks-a subset of small-world networks. Notably, well-known tumor-suppressive miRNAs (Let-7, miR-15/16, 26, 29, 31, 34, 145, 200, 203-205, 223, and 375) collectively have more than expected target genes, and well-known cancer genes contain more than expected miRNA binding sites. In summary, miRNA target site distribution exhibits characteristics of the small-world network. The potential to use this pattern to better understand miRNA function and their oncological roles is discussed.

Involvement of miR-451 in resistance to paclitaxel by regulating YWHAZ in breast cancer

MicroRNAs (miRNAs) have been identified as major post-transcriptional regulators of the initiation and progression of human cancers, including breast cancer. However, the detail role of miR-451 has not been fully elucidated in breast cancer. In this study, we aimed to investigate the biological role and molecular mechanisms of miR-451 in drug resistance in breast cancer cell lines and in xenograft model. We show that miR-451 is decreased in human breast cancer specimens and in paclitaxel-resistant (PR) cells. Ectopic expression of miR-451 could inhibit the cell migration and invasion, promoted apoptosis, induced cell-cycle arrest Furthermore, tyrosine3-monooxygenase/tryptophan5-monooxygenase activation protein zeta (YWHAZ) was identified as a direct target of miR-451. Remarkably, the expression of YWHAZ is inversely correlated with the level of miR-451 in human breast cancer samples. Co-treatment with miR-451 mimics and YWHAZ-siRNA significantly enhanced YWHAZ knockdown in both SKBR3/PR and MCF-7/PR cells Moreover, miR-451 markedly inhibited expression of β-catenin via YWHAZ and subsequently inhibited downstream gene cyclin D1, c-Myc expression. The results of xenograft model in vivo showed that intratumor injection of miR-451 agomir induced a tumor-suppressive effect in SKBR3/PR drug-resistant xenograft model. Taken together, our findings suggested that miR-451 might be considered as important and potential target in paclitaxel-resistant breast cancer treatment.

Construction of miRNA-miRNA networks revealing the complexity of miRNA-mediated mechanisms in trastuzumab treated breast cancer cell lines

Trastuzumab is a monoclonal antibody frequently used to prevent the progression of HER2+ breast cancers, which constitute approximately 20% of invasive breast cancers. microRNAs (miRNAs) are small, non-coding RNA molecules that are known to be involved in gene regulation. With their emerging roles in cancer, they are recently promoted as potential candidates to mediate therapeutic actions by targeting genes associated with drug response. In this study we explored miRNA-mediated regulation of trastuzumab mechanisms by identifying the important miRNAs responsible for the drug response via homogenous network analysis. Our network model enabled us to simplify the complexity of miRNA interactions by connecting them through their common pathways. We outlined the functionally relevant miRNAs by constructing pathway-based miRNA-miRNA networks in SKBR3 and BT474 cells, respectively. Identification of the most targeted genes revealed that trastuzumab responsive miRNAs favourably regulate the repression of targets with longer 3’UTR than average considered to be key elements, while the miRNA-miRNA networks highlighted central miRNAs such as hsa-miR-3976 and hsa-miR-3671 that showed strong interactions with the remaining members of the network. Furthermore, the clusters of the miRNA-miRNA networks showed that trastuzumab response was mostly established through cancer related and metabolic pathways. hsa-miR-216b was found to be the part of the most powerful interactions of metabolic pathways, which was defined in the largest clusters in both cell lines. The network based representation of miRNA-miRNA interactions through their shared pathways provided a better understanding of miRNA-mediated drug response and could be suggested for further characterization of miRNA functions.

Tumor suppressor role of miR-3622b-5p in ERBB2-positive cancer

Over-expression or amplification of ERBB2 is observed in multifarious carcinomas. However, the molecular mechanism of ERBB2 downregulation in ERBB2-positive cancers remains obscure. This experiment investigated the suppressive role of miR-3622b-5p in ERBB2-positive breast and gastric cancers. The luciferase activity of ERBB2 3′-untranslated region-based reporters constructed in HEK-293T, SK-BR-3 and MCF-10A cells suggested that ERBB2 was the target gene of miR-3622b-5p. Over-expressed miR-3622b-5p reduced the protein level of ERBB2, weakened the activation of mTORC1/S6, and induced the apoptosis of ERBB2-positive cancer cells. MiR-3622b-5p was significantly down-regulated in breast and gastric cancer tissues. This down-regulation in ERBB2-positive breast and gastric cancer tissues was more obvious than that in ERBB2-negative breast and gastric cancer tissues. MiR-3622b-5p turned ERBB2-positive cancer cells more vulnerable to the apoptosis induced by cisplatin and 5-fluorouracil. Taken together, miR-3622b-5p is involved in the proliferation and apoptosis of human ERBB2-positive cancer cells via targeting ERBB2/mTORC1 signaling pathway.

Exosomes as mediators of platinum resistance in ovarian cancer

Exosomes have been implicated in the cell-cell transfer of oncogenic proteins and genetic material. We speculated this may be one mechanism by which an intrinsically platinum-resistant population of epithelial ovarian cancer (EOC) cells imparts its influence on surrounding tumor cells. To explore this possibility we utilized a platinum-sensitive cell line, A2780 and exosomes derived from its resistant subclones, and an unselected, platinum-resistant EOC line, OVCAR10. A2780 cells demonstrate a ~2-fold increase in viability upon treatment with carboplatin when pre-exposed to exosomes from platinum-resistant cells as compared to controls. This coincided with increased epithelial to mesenchymal transition (EMT). DNA sequencing of EOC cell lines revealed previously unreported somatic mutations in the Mothers Against Decapentaplegic Homolog 4 (SMAD4) within platinum-resistant cells. A2780 cells engineered to exogenously express these SMAD4 mutations demonstrate up-regulation of EMT markers following carboplatin treatment, are more resistant to carboplatin, and release exosomes which impart a ~1.7-fold increase in resistance in naive A2780 recipient cells as compared to controls. These studies provide the first evidence that acquired SMAD4 mutations enhance the chemo-resistance profile of EOC and present a novel mechanism in which exchange of tumor-derived exosomes perpetuates an EMT phenotype, leading to the development of subpopulations of platinum-refractory cells.

microRNAs Make the Call in Cancer Personalized Medicine

Since their discovery and the advent of RNA interference, microRNAs have drawn enormous attention because of their ubiquitous involvement in cellular pathways from life to death, from metabolism to communication. It is also widely accepted that they possess an undeniable role in cancer both as tumor suppressors and tumor promoters modulating cell proliferation and migration, epithelial-mesenchymal transition and tumor cell invasion and metastasis. Moreover, microRNAs can even affect the tumor surrounding environment influencing angiogenesis and immune system activation and recruitment. The tight association of microRNAs with several cancer-related processes makes them undoubtedly connected to the effect of specific cancer drugs inducing either resistance or sensitization. In this context, personalized medicine through microRNAs arose recently with the discovery of single nucleotide polymorphisms in the target binding sites, in the sequence of the microRNA itself or in microRNA biogenesis related genes, increasing risk, susceptibility and progression of multiple types of cancer in different sets of the population. The depicted scenario implies that the overall variation displayed by these small non-coding RNAs have an impact on patient-specific pharmacokinetics and pharmacodynamics of cancer drugs, pushing on a rising need of personalized treatment. Indeed, microRNAs from either tissues or liquid biopsies are also extensively studied as valuable biomarkers for disease early recognition, progression and prognosis. Despite microRNAs being intensively studied in recent years, a comprehensive review describing these topics all in one is missing. Here we report an up-to-date and critical summary of microRNAs as tools for better understanding personalized cancer biogenesis, evolution, diagnosis and treatment.