MiRNA 17 family regulates cisplatin-resistant and metastasis by targeting TGFbetaR2 in NSCLC

LncRNA HOTAIR influences cell growth, migration, invasion, and apoptosis via the miR-20a-5p/HMGA2 axis in breast cancer

To study the regulatory effect of lncRNA HOTAIR/miR-20a-5p/HMGA2 axis on breast cancer (BC) cell growth, cell mobility, invasiveness, and apoptosis. The microarray data of lncRNAs and mRNAs with differential expression in BC tissues were analyzed in the Cancer Genome Atlas (TCGA) database. LncRNA HOX transcript antisense RNA (lncRNA HOTAIR) expression in BC was assessed by qRT-PCR. Cell viability was confirmed using MTT and colony formation assay. Cell apoptosis was analyzed by TdT-mediated dUTP nick-end labeling (TUNEL) assay. Cell mobility and invasiveness were testified by transwell assay. RNA pull-down and dual luciferase assay were used for analysis of the correlation between lncRNA HOTAIR and miR-20a-5p, as well as relationship of miR-20a-5p with high mobility group AT-hook 2 (HMGA2). Tumor xenograft study was applied to confirm the correlation of lncRNA HOTAIR/miR-20a-5p/HMGA2 axis on BC development in vivo. The expression levels of the lncRNA HOTAIR were upregulated in BC tissues and cells. Knockdown lncRNA HOTAIR inhibited cell propagation and metastasis and facilitated cell apoptosis. MiR-20a-5p was a target of lncRNA HOTAIR and had a negative correlation with lncRNA HOTAIR. MiR-20a-5p overexpression in BC suppressed cell growth, mobility, and invasiveness and facilitated apoptosis. HMGA2 was a target of miR-20a-5p, which significantly induced carcinogenesis of BC. BC cells progression was mediated by lncRNA HOTAIR via affecting miR-20a-5p/HMGA2 in vivo. LncRNA HOTAIR affected cell growth, metastasis, and apoptosis via the miR-20a-5p/HMGA2 axis in breast cancer.

miR-7 reverses the resistance to BRAFi in melanoma by targeting EGFR/IGF-1R/CRAF and inhibiting the MAPK and PI3K/AKT signaling pathways

MicroRNAs (miRNAs) are attractive therapeutic targets for various therapy-resistant tumors. However, the association between miRNA and BRAF inhibitor resistance in melanoma remains to be elucidated. We used microarray analysis to comprehensively study the miRNA expression profiling of vemurafenib resistant (VemR) A375 melanoma cells in relation to parental A375 melanoma cells. MicroRNA-7 (miR-7) was identified to be the most significantly down-regulated miRNA in VemR A375 melanoma cells. We also found that miR-7 was down-regulated in Mel-CVR cells (vemurafenib resistant Mel-CV melanoma cells). Reestablishment of miR-7 expression could reverse the resistance of both cells to vemurafenib. We showed that epidermal growth factor receptor (EGFR), insulin-like growth factor-1 receptor (IGF-1R) and CRAF were over-expressed in VemR A375 melanoma cells. Introduction of miR-7 mimics could markedly decrease the expressions of EGFR, IGF-1R and CRAF and further suppressed the activation of MAPK and PI3K/AKT pathway in VemR A375 melanoma cells. Furthermore, tumor growth was inhibited in an in vivo murine VemR A375 melanoma tumor model transfected with miR-7 mimics. Collectively, our study demonstrated that miR-7 could reverse the resistance to BRAF inhibitors in certain vemurafenib resistant melanoma cell lines. It could advance the field and provide the basis for further studies in BRAF inhibitor resistance in melanoma.

Biology of MiR-17-92 Cluster and Its Progress in Lung Cancer

MicroRNAs, a class of short endogenous RNAs, acting as post-transcriptional regulators of gene expression, mostly silence gene expression via binding imperfectly matched sequences in the 3'UTR of target mRNA. MiR-17-92, a highly conserved gene cluster, has 6 members including miR-17, miR-18a, miR-19a, miR-20a, miR-19b-1 and miR-92a. The miR-17-92 cluster, regarded as oncogene, is overexpressed in human cancers. Lung cancer is the leading cause of death all over the world. The molecular mechanism of lung cancer has been partly known at the levels of genes and proteins in last decade. However, new prognosis biomarkers and more target drugs should be developed in future. Therefore, noncoding RNAs, especially miRNAs, make them as new potentially clinical biomarkers for diagnosis and prognosis. In this review, we focus the current progress of miR-17-92 cluster in lung cancer.

MicroRNAs as regulators of cisplatin-resistance in non-small cell lung carcinomas

With more than 80% of all diagnosed lung cancer cases, non-small cell lung cancer (NSCLC) remains the leading cause of cancer death worldwide. Exact diagnosis is mostly very late and advanced-stage NSCLCs are inoperable at admission. Tailored therapies with tyrosine kinase inhibitors are only available for a minority of patients. Thus, chemotherapy is often the treatment of choice. As first-line chemotherapy for NSCLCs, platinum-based substances (e.g. cisplatin, CDDP) are mainly used. Unfortunately, the positive effects of CDDP are frequently diminished due to development of drug resistance and negative influence of microenvironmental factors like hypoxia. MicroRNAs (miRNAs) are small, non-coding molecules involved in the regulation of gene expression and modification of biological processes like cell proliferation, apoptosis and cell response to chemotherapeutics. Expression of miRNAs is often deregulated in lung cancer compared to corresponding non-malignant tissue. In this review we summarize the present knowledge about the effects of miRNAs on CDDP-resistance in NSCLCs. Further, we focus on miRNAs deregulated by hypoxia, which is an important factor in the development of CDDP-resistance in NSCLCs. This review will contribute to the general understanding of miRNA-regulated biological processes in NSCLC, with special focus on the role of miRNA in CDDP-resistance.

A miR-20a/MAPK1/c-Myc regulatory feedback loop regulates breast carcinogenesis and chemoresistance

Chemoresistance often leads to the failure of breast cancer treatment. MicroRNAs (miRNAs) play an important role in the progression and chemoresistance of cancer. However, because of the complexity of the mechanisms of chemoresistance and the specificity of miRNA regulation in different cell types, the function of miR-20a in breast cancer chemoresistance is still unclear. Here, by using miRNA microarray and high-content screening techniques, we found that miR-20a/b were significantly downregulated in breast cancer tissues compared with normal breast tissues, and low miR-20a/b expression was correlated with poor survival in breast cancer patients. Ectopic overexpression of miR-20a sensitized breast cancer cells to a broad spectrum of chemotherapy drugs and suppress their proliferation both in vitro and in vivo. Further study demonstrated that miR-20a directly targeted the 3'untranslated region of MAPK1, and thus downregulated the expression of P-gp and c-Myc by inhibiting the MAPK/ERK signaling pathway, whereas c-Myc can bind to the promoter region of the miR-20a gene to promote the expression of miR-20a. Together, our study identified a novel miR-20a/MAPK1/c-Myc feedback loop that regulates breast cancer growth and chemoresistance. These findings suggest that miR-20a synergizing with anticancer drugs will be a promising treatment strategy, especially for chemoresistant patients.

MiR-106a-5p inhibits the cell migration and invasion of renal cell carcinoma through targeting PAK5

MicroRNA-106a-5p (MiR-106a-5p), a small non-coding RNA, has been reported to be downregulated in astrocytoma, osteosarcoma and colorectal cancer. However, the expression levels and biological function in renal cell carcinoma (RCC) have not been studied yet. In this study, we found that the miR-106a-5p was significantly downregulated in RCC tissues and cell lines, and that overexpression of miR-106a-5p led to decreased cell metastasis ability in a xenograft model. Inhibition of miR-106a-5p in RCC cell lines altered the cell migration, invasion and wound healing abilities. Mechanistic studies demonstrated that miR-106a-5p directly bound to the 3'-UTR of the PAK5 mRNA and mediated a decrease in the protein expression of PAK5. We further proved that PAK5 protein levels were negatively correlated with the miR-106a-5p expression in both patient samples and xenograft model. In epigenetics, methylation specific PCR experiments indicated that the upstream gene promoter of miR-106a-5p was hypermethylated in RCC, which might be responsible for its downregulation. Our findings suggested that miR-106a-5p might be a potential gene therapy target for the treatment of RCC metastasis.

LncRNA MEG3 enhances cisplatin sensitivity in non-small cell lung cancer by regulating miR-21-5p/SOX7 axis

Background

Long noncoding RNAs (lncRNAs) have been revealed to play essential role in drug resistance of multiple cancers. LncRNA MEG3 was previously reported to be associated with cisplatin (DDP) resistance in non-small cell lung cancer (NSCLC) cells. However, the molecular mechanism of MEG3 affecting DDP resistance in NSCLC remains to be further illustrated. In this study, we attempted to discuss whether MEG3 also could function as a competing endogenous RNA to regulate DDP resistance in NSCLC.

Materials and methods

The expression of MEG3, miR-21-5p, and sex-determining region Y-box 7 (SOX7) in NSCLC tissues or cells was examined by quantitative real-time polymerase chain reaction (qRT-PCR). 3-(4,5-Dimethylthazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), flow cytometry, and caspase-3 activity analysis were applied to assess the DDP sensitivity of NSCLC cells. The interaction between MEG3, miR-21-5p, and SOX7 was explored by luciferase reporter assay, RNA immunoprecipitation (RIP) assay, qRT-PCR, and Western blot. Mouse NSCLC transplanted tumor was established to verify the functional role of MEG3 in DDP resistance in vivo.

Results

MEG3 was downregulated in DDP-resistant NSCLC cells. Overexpression of MEG3 enhanced DDP sensitivity of NSCLC cells in vitro. MEG3 directly interacted with miR-21-5p and suppressed its expression. miR-21-5p significantly abolished the effects of MEG3 on DDP resistance via modulating cell proliferation and apoptosis. SOX7 was identified as a direct target of miR-21-5p and MEG3 positively regulated SOX7 expression by suppressing miR-21-5p. Moreover, MEG3 knockdown-induced pro-proliferative and anti-apoptotic effects were reversed in DDP-resistant NSCLC cells by upregulating SOX7. Furthermore, upregulation of MEG3 induced sensitivity of NSCLC cells to DDP in vivo.

Conclusion

MEG3 overexpression induced DDP sensitivity of NSCLC cells by regulating miR-21-5p/SOX7 axis, shedding light on the molecular mechanism of MEG3 involved in the development of DDP resistance of NSCLC cells.

Roles of microRNAs in the resistance to platinum based chemotherapy in the non-small cell lung cancer

Platinum-based adjuvant chemotherapy improves survival among patients with lung tumors, in particular non-small cell lung cancer (NSCLC). But the predicament of drug resistance in NSCLC patients is frustrating us. The profiles of microRNAs are different between platinum chemotherapy resistant and sensitive NSCLC cells. Researches regarding microRNAs and their targets, in platinum drug resistant cases, illuminate novel ideals for platinum-based chemotherapy for NSCLC patients. Therefore, in this review we will focus on three aspects: Epithelial-mesenchymal transition (EMT), cell proliferation and apoptosis, and the roles of microRNAs in cisplatin (CDDP) and carboplatin (CBP) resistance.

Epithelial-to-Mesenchymal Transition and MicroRNAs in Lung Cancer

Despite major advances, non-small cell lung cancer (NSCLC) remains the major cause of cancer-related death in developed countries. Metastasis and drug resistance are the main factors contributing to relapse and death. Epithelial-to-mesenchymal transition (EMT) is a complex molecular and cellular process involved in tissue remodelling that was extensively studied as an actor of tumour progression, metastasis and drug resistance in many cancer types and in lung cancers. Here we described with an emphasis on NSCLC how the changes in signalling pathways, transcription factors expression or microRNAs that occur in cancer promote EMT. Understanding the biology of EMT will help to define reversing process and treatment strategies. We will see that this complex mechanism is related to inflammation, cell mobility and stem cell features and that it is a dynamic process. The existence of intermediate phenotypes and tumour heterogeneity may be debated in the literature concerning EMT markers, EMT signatures and clinical consequences in NSCLC. However, given the role of EMT in metastasis and in drug resistance the development of EMT inhibitors is an interesting approach to counteract tumour progression and drug resistance. This review describes EMT involvement in cancer with an emphasis on NSCLC and microRNA regulation.

MicroRNA-19a promotes nasopharyngeal carcinoma by targeting transforming growth factor β receptor 2

MicroRNA (miR), a class of small non-coding RNA, function as key regulators in gene expression through directly binding to the 3' untranslated region of their target mRNA, which further leads to translational repression or mRNA degradation. miR-19a, a member of miR-17-92 cluster, has an oncogenic role in a variety of malignant tumors. However, the exact role of miR-19a in nasopharyngeal carcinoma (NPC) has not previously been studied. The present study aimed to investigate the function and mechanism of miR-19a in regulating the viability and invasion of NPC cells. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) data indicated that the expression levels of miR-17-92 cluster members (miR-17, miR-18a, miR-19a and miR-20a) were frequently increased in NPC tissues compared to the normal tissues. It was also demonstrated that miR-19a was significantly upregulated in NPC C666-1 cells compared to NP69 cells (P<0.01). Knockdown of miR-19a led to a significant decrease in the viability and invasion of NPC C666-1 cells (P<0.01), and induced increased protein expression levels of transforming growth factor β receptor 2 (TGFβR2), which was further identified as a direct target gene of miR-19a by using a luciferase reporter assay. Overexpression of TGFβR2 also suppressed the viability and invasion of C666-1 cells, similar to the effects of miR-19a inhibition. Furthermore, knockdown of TGFβR2 reversed the suppressive effects of miR-19a inhibition on C666-1 cell viability and invasion, suggesting that the role of miR-19a in mediating cell viability and invasion is through directly targeting TGFβR2 in NPC cells. In addition, RT-qPCR data demonstrated that the mRNA expression level of TGFβR2 was markedly reduced in NPC tissues and C666-1 cells. In summary, the present study demonstrated an oncogenic role of miR-19a in NPC via mediation of TGFβR2. Therefore, miR-19a may be a potential therapeutic target for NPC.

MicroRNA-20a contributes to cisplatin-resistance and migration of OVCAR3 ovarian cancer cell line

MicroRNAs (miRs) have been reported to be associated with the development of numerous types of cancer. However, the function of miRs in human ovarian carcinoma chemoresistance remains largely undefined. In the present study, cell chemotherapy combined with a Cell Counting Kit-8 assay demonstrated that miR-20a performed important roles in ovarian cancer cells chemoresistance. Flow cytometry, cellular proliferation assays and Transwell assays results revealed that the proliferation and migration rates of OVCAR3/DDP cells were increased in comparison with parental cells. Western blot analysis results suggested that epithelial-mesenchymal transition (EMT) activated by miR-20a contributed to OVCAR3/DDP cell migration. The present study highlighted the importance of miR-20a in regulating the chemoresistant properties of OVCAR3 cells and promoting cisplatin-resistant cell migration by activating EMT. The results of present study may therefore provide novel insights into reversing the chemoresistance of ovarian cancer and improving its treatment.

MicroRNA-17-5p inhibits proliferation and triggers apoptosis in non-small cell lung cancer by targeting transforming growth factor β receptor 2

MicroRNAs (miRs) are small non-coding RNAs that suppress gene expression by directly binding to the 3′-untranslated region of their target mRNAs. Specific miRs serve key roles in the development and progression of non-small cell lung cancer (NSCLC). The aim of the present study was to determine the mechanism of miR-17-5p in the regulation of NSCLC cell survival and proliferation. Reverse transcription-quantitative polymerase chain reaction data indicated that miR-17-5p was significantly downregulated in 28 NSCLC tissues compared with 7 non-tumorous lung tissues. Furthermore, lower miR-17-5p expression was associated with a higher pathological stage in NSCLC patients. Lower miR-17-5p expression was also observed in several common NSCLC cell lines, including SK-MES-1, A549, SPCA-1, H460, H1229 and HCC827, compared with the bronchial epithelium cell line, BEAS-2B. Additionally, overexpression of miR-17-5p significantly inhibited proliferation while inducing the apoptosis of NSCLC H460 cells. Subsequently, transforming growth factor β receptor 2 (TGFβR2) was identified as a direct target of miR-17-5p using a luciferase reporter assay. Western blot analysis confirmed that miR-17-5p negatively mediated the expression of TGFβR2 in NSCLC cells. Furthermore, small interfering RNA-induced downregulation of TGFβR2 also suppressed the proliferation of H460 cells while triggering apoptosis. Therefore, the results of the current study suggest that miR-17-5p may inhibit proliferation and trigger apoptosis in NSCLC H460 cells at least partially by targeting TGFβR2.

Interactions between anticancer active platinum complexes and non-coding RNAs/microRNAs

Platinum(II) complexes such as cisplatin, carboplatin and oxaliplatin are clinically approved for the therapy of various solid tumors. Challenging pathogenic properties of cancer cells and the response of cancers towards platinum-based drugs are strongly influenced by non-coding small RNA molecules, the microRNAs (miRNAs). Both increased platinum activity and formation of tumor resistance towards platinum drugs are controlled by miRNAs. This review gives an overview of the interactions between platinum-based drugs and miRNAs, and their influence on platinum activity in various cancer types is discussed.

Disturbance of the let-7/LIN28 double-negative feedback loop is associated with radio- and chemo-resistance in non-small cell lung cancer

Radio- and chemo-resistance represent major obstacles in the therapy of non-small-cell lung cancer (NSCLC) and the underlying molecular mechanisms are not known. In the present study, during induction of radio- or chemo-resistance in NSCLC cells, dynamic analyses revealed that decreased expression of let-7 induced by irradiation or cisplatin resulted in increased expression of its target gene LIN28, and increased expression of LIN28 then contributed to further decreased expression of let-7 by inhibiting its maturation and biogenesis. Moreover, we showed that down-regulation of let-7 and up-regulation of LIN28 expression promoted resistance to irradiation or cisplatin by regulating the single-cell proliferative capability of NSCLC cells. Consequently, in NSCLC cells, let-7 and LIN28 can form a double-negative feedback loop through mutual inhibition, and disturbance of the let-7/LIN28 double-negative feedback loop induced by irradiation or chemotherapeutic drugs can result in radio- and chemo-resistance. In addition, low expression of let-7 and high expression of LIN28 in NSCLC patients was associated significantly with resistance to radiotherapy or chemotherapy. Therefore, our study demonstrated that disturbance of the let-7/LIN28 double-negative feedback loop is involved in the regulation of radio- and chemo-resistance, and that let-7 and LIN28 could be employed as predictive biomarkers of response to radiotherapy or chemotherapy in NSCLC patients.

Serum miR-20a is a promising biomarker for gastric cancer

Gastric cancer (GC) is a common type of cancer, particularly in China. Numerous studies have demonstrated that circulating microRNAs (miRNAs) have potential applications as noninvasive biomarkers for cancer diagnosis and prognosis. Microarray-based serum miRNA profiling was performed on the serum of 12 paired pre- and post-operative GC patients to screen differentially expressed serum miRNAs. Twelve different serum miRNAs between pre- and post-operative GC patients were identified. Those miRNAs were verified by real-time quantitative polymerase chain reaction in 110 paired pre- and post-operative serum samples from 55 GC patients. miR-20a was confirmed and demonstrated potential as a GC-associated biomarker. Furthermore, the levels of serum miR-20a were significantly different between GC, nasopharyngeal cancer, colorectal carcinoma, breast cancer and non-cancerous controls. In addition, it was found that serum miR-20a levels correlated with age, tumor stage, differentiated degree and lymph node metastasis in GC. Survival analysis indicated that GC patients with elevated levels of serum miR-20a had poor survival. Thus, serum miR-20a may serve as a molecular marker for diagnosis, evaluating therapeutic efficacy and prognosis, as well as monitoring recurrence in GC patients.

MiR-20b Displays Tumor-Suppressor Functions in Papillary Thyroid Carcinoma by Regulating the MAPK/ERK Signaling Pathway

BACKGROUND

MicroRNAs (miRNAs) are endogenous, small, non-coding RNAs that play important roles in multiple biological processes. MiR-20b has been reported to be dysregulated in papillary thyroid carcinoma (PTC). However, the functional roles are still largely unknown. This study aimed to investigate the biological functions and the underlying molecular mechanisms of miR-20b in PTC.

METHOD

The expression of miR-20b was assessed by quantitative reverse transcription polymerase chain reaction in 47 pairs of PTC and adjacent normal thyroid tissues. The association between miR-20b expression and clinicopathologic status of PTC patients was analyzed. MiR-20b was overexpressed in the PTC cell lines K1 and TPC-1, and the effects on cell viability, migration, and invasion were evaluated. The study further searched for targets of miR-20b, and identified the possible molecular mechanisms of miR-20b in PTC cells. Additionally, the effect of miR-20b on tumor growth in nude mice was assessed.

RESULTS

It was found that miR-20b was markedly downregulated in PTC tissues compared with their adjacent normal thyroid tissues. The low-level expression of miR-20b was correlated with cervical lymph node metastasis and TNM staging. Upregulation of miR-20b inhibited cell viability, migration, and invasion in K1 and TPC-1 cells. Ectopic overexpression of miR-20b could suppress the mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) signaling pathway through directly targeting son of sevenless homolog 1 (SOS1) and extracellular signal-regulated kinase 2 (ERK2). Furthermore, depletion of SOS1 or ERK2 by siRNAs has similar effects as miR-20b overexpression on cell viability and invasion, whereas rescued SOS1 or ERK2 expression partially reversed the inhibitory effects of miR-20b in TPC cell lines. In xenograft animal experiments, it was found that overexpressed miR-20b could suppress tumor growth of PTC cells.

CONCLUSION

These results indicate for the first time that miR-20b displays tumor-suppressor functions in PTC. By targeting SOS1 and ERK2, miR-20b inhibits the activity of the MAPK/ERK signaling pathway. The findings suggest that miR-20b may play an important role in PTC initiation, progression, and metastasis, and may provide a potential therapeutic target for PTC.

MicroRNA-20a-5p contributes to hepatic glycogen synthesis through targeting p63 to regulate p53 and PTEN expression

Recently, it is implicated that aberrant expression of microRNAs (miRs) is associated with insulin resistance. However, the role of miR-17 family in hepatic insulin resistance and its underlying mechanisms remain unknown. In this study, we provided mechanistic insight into the effects of miR-20a-5p, a member of miR-17 family, on the regulation of AKT/GSK pathway and glycogenesis in hepatocytes. MiR-20a-5p was down-regulated in the liver of db/db mice, and NCTC1469 cells and Hep1-6 cells treated with high glucose, accompanied by reduced glycogen content and impaired insulin signalling. Notably, inhibition of miR-20a-5p significantly reduced glycogen synthesis and AKT/GSK activation, whereas overexpression of miR-20a-5p led to elevated glycogenesis and activated AKT/GSK signalling pathway. In addition, miR-20a-5p mimic could reverse high glucose-induced impaired glycogenesis and AKT/GSK activation in NCTC1469 and Hep1-6 cells. P63 was identified as a target of miR-20a-5p by bioinformatics analysis and luciferase reporter assay. Knockdown of p63 in the NCTC1469 cells and the Hep1-6 cells by transfecting with siRNA targeting p63 could increase glycogen content and reverse miR-20a-5p inhibition-induced reduced glycogenesis and activation of AKT and GSK, suggesting that p63 participated in miR-20a-5p-mediated glycogenesis in hepatocytes. Moreover, our results indicate that p63 might directly bind to p53, thereby regulating PTEN expression and in turn participating in glycogenesis. In conclusion, we found novel evidence suggesting that as a member of miR-17 family, miR-20a-5p contributes to hepatic glycogen synthesis through targeting p63 to regulate p53 and PTEN expression.

MicroRNA-20a-5p contributes to hepatic glycogen synthesis through targeting p63 to regulate p53 and PTEN expression

Recently, it is implicated that aberrant expression of microRNAs (miRs) is associated with insulin resistance. However, the role of miR‐17 family in hepatic insulin resistance and its underlying mechanisms remain unknown. In this study, we provided mechanistic insight into the effects of miR‐20a‐5p, a member of miR‐17 family, on the regulation of AKT/GSK pathway and glycogenesis in hepatocytes. MiR‐20a‐5p was down‐regulated in the liver of db/db mice, and NCTC1469 cells and Hep1‐6 cells treated with high glucose, accompanied by reduced glycogen content and impaired insulin signalling. Notably, inhibition of miR‐20a‐5p significantly reduced glycogen synthesis and AKT/GSK activation, whereas overexpression of miR‐20a‐5p led to elevated glycogenesis and activated AKT/GSK signalling pathway. In addition, miR‐20a‐5p mimic could reverse high glucose‐induced impaired glycogenesis and AKT/GSK activation in NCTC1469 and Hep1‐6 cells. P63 was identified as a target of miR‐20a‐5p by bioinformatics analysis and luciferase reporter assay. Knockdown of p63 in the NCTC1469 cells and the Hep1‐6 cells by transfecting with siRNA targeting p63 could increase glycogen content and reverse miR‐20a‐5p inhibition‐induced reduced glycogenesis and activation of AKT and GSK, suggesting that p63 participated in miR‐20a‐5p‐mediated glycogenesis in hepatocytes. Moreover, our results indicate that p63 might directly bind to p53, thereby regulating PTEN expression and in turn participating in glycogenesis. In conclusion, we found novel evidence suggesting that as a member of miR‐17 family, miR‐20a‐5p contributes to hepatic glycogen synthesis through targeting p63 to regulate p53 and PTEN expression.

miR-17-92 plays an oncogenic role and conveys chemo-resistance to cisplatin in human prostate cancer cells

The mir-17-92 cluster consists of six mature miRNAs and is implicated in diverse human cancers by targeting mRNAs involved in distinct pathways that either promote or inhibit carcinogenesis. However, the molecular mechanism underlying the mir-17-92 cluster-mediated pro-tumorigenic or anti-tumorigenic effects has not been clearly elucidated in prostate cancer. In the present study, the role of the mir-17-92 cluster in diverse aspects of prostate cancer cells has been thoroughly investigated. Forced introduction of the mir-17-92 cluster into the androgen-independent DU145 prostate cancer cells evidently promoted cell growth due to disruption of the balance between cellular proliferation and apoptosis. Overexpression of the mir-17-92 cluster significantly improved the migration and invasion of the DU145 cells, attributed to the induction of integrin β-1. Notably, the mir-17-92 cluster conveyed chemo-resistance to cisplatin. We demonstrated that the mir-17-92 cluster suppressed the expression of inhibitor of the AKT signaling pathway and activated the AKT pathway subsequently, which played a central role in regulating cellular proliferation, apoptosis and chemo-resistance. Continuously activated ERK1/2 signaling also contributed importantly to these processes. The present study provides key evidence for crucial oncogenic role of the miR-17-92 cluster in prostate cancer cells. Further investigations are warranted to determine whether miR-17-92 cluster can be targeted for future treatment of human prostate cancer.

MicroRNAs, TGF-β signaling, and the inflammatory microenvironment in cancer

Inflammatory cells and mediators form a major part of the tumor microenvironment and play important roles in the regulation of cancer initiation, tumor cell proliferation, and metastasis. MicroRNAs (miRNAs) play important roles in several physiological and pathological processes, including the regulation of the inflammatory microenvironment in cancer. Transforming growth factor-β (TGF-β) is an inflammation-related cytokine that functions in both tumor suppression and promotion; however, its underlying molecular mechanisms remain unclear. Recent evidence indicates an association between miRNAs and TGF-β signaling, providing new insight into the nature of the inflammatory microenvironment in cancer. The present review is an overview of the interaction between miRNAs and inflammatory cytokines, with emphasis on the cross talk between TGF-β signaling and miRNAs and their influence on cancer cell behavior. The emerging roles of miRNAs in cancer-related inflammation and the potential to target miRNA signaling pathways for cancer therapy are also discussed.

Molecular mechanisms of microRNAs in regulating epithelial-mesenchymal transitions in human cancers

The epithelial-mesenchymal transition (EMT) provides a strong driving force in the progression of various human cancers and the development of chemoresistance. Recently, numbers of studies have demonstrated that microRNAs (miRNAs), by post-transcriptionally silencing EMT-related molecules, can promote or inhibit the EMT process and play pivotal roles in effectively manipulating the occurrence, development, invasion, and metastasis of cancers. MiRNAs can also control the EMT or be controlled by genetic modification and mutual regulation, especially negative feedback. Therefore, miRNAs can be viewed as either oncogenes or tumor suppressor genes to facilitate or retard the EMT, resulting in far-reaching impact on tumor metastasis and effective diagnosis, treatment, and prognosis.

The regulatory and predictive functions of miR-17 and miR-92 families on cisplatin resistance of non-small cell lung cancer

Background

Chemotherapy is an important therapeutic approach for non-small cell lung cancer (NSCLC). However, a successful long-term treatment can be prevented by the occurring of chemotherapy resistance frequently, and the molecular mechanisms of chemotherapy resistance in NSCLC remain unclear. In this study, abnormal expressions of miR-17 and miR-92 families are observed in cisplatin-resistant cells, suggesting that miR-17 and miR-92 families are involved in the regulation of cisplatin resistance in NSCLC.

Methods

miRNA microarray shows that miR-17 and miR-92 families are all down-regulated in cisplatin-resistant A549/DDP cells compared with cisplatin-sensitive A549 cells. The aim of this study is to investigate the regulatory functions of miR-17 and miR-92 families on the formation of cisplatin resistance and the predictive functions of them as biomarkers of platinum-based chemotherapy resistance in NSCLC.

Results

The low expressions of miR-17 and miR-92 families can maintain cisplatin resistance through the regulation of CDKN1A and RAD21. As a result of high expressions of CDKN1A and RAD21, the inhibition of DNA synthesis and the repair of DNA damage are achieved and these may be two major contributing factors to cisplatin resistance. Moreover, we demonstrate that the expressions of miR-17 and miR-92 families in NSCLC tissues are significantly associated with platinum-based chemotherapy response.

Conclusion

Our study indicates that miR-17 and miR-92 families play important roles in cisplatin resistance and can be used as potential biomarkers for better predicting the clinical response to platinum-based chemotherapy in NSCLC.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1713-z) contains supplementary material, which is available to authorized users.

MicroRNA-129-5p modulates epithelial-to-mesenchymal transition by targeting SIP1 and SOX4 during peritoneal dialysis

Peritoneal dialysis (PD) is the most readily feasible home-dialysis method for renal replacement therapy. However, repeated use of PD can lead to induction of mesothelial/epithelial-mesenchymal transition (MMT/EMT) and fibrosis, eventually leading to ultrafiltration failure and discontinuation of PD. MicroRNA-129-5p (miR-129-5p) is believed to be a potent downstream inhibitor of TGF-β1 in renal fibrosis, but the effect of miR-129-5p on MMT/EMT relevant to PD is unknown. In this study, as determined by microRNA array analysis and confirmed by northern blot analysis and real-time PCR, we demonstrate that miRNA-129-5p is decreased in mesothelial cells isolated from effluent of patients having PD for more than 6 months extending to several years compared with those who have undergone PD for less than 6 months. The decreased expression of miR-129-5p was accompanied with alterations in EMT-related genes and the expression of respective proteins in vivo. In addition, in in vitro studies we noted that the expression of E-cadherin and claudin-1 were significantly reduced with increased cell migration in HMrSV5, a human peritoneal mesothelial cell line (HPMC), treated with TGF-β1, whereas expression of vimentin, fibronectin and transcription factors SIP1 and SOX4 increased significantly, as assessed by real-time PCR, western blot analysis and immunofluorescence microscopy. Furthermore, alteration in EMT-related genes and proteins were reversed by overexpression of miR-129-5p. No effect was observed in cells treated with miR-negative control. Meanwhile, inhibition of SIP1 and SOX4 with their respective siRNA also could decrease the expression of EMT-related genes and protein levels in HPMCs induced with TGF-β1. Finally, we demonstrate that SIP1 can inhibit the promoter activity of E-cadherin while enhancing the promoter activity of vimentin. We also observed that miR-129-5p could directly target the 3'UTR of SIP1 and SOX4 genes, and repressed their post-transcriptional activities. These data suggest that there is a novel TGF-β1/miR-129-5p/SIP-1 or SOX4 pathway that has a significant role in MMT and fibrosis in the setting of PD.

Matrine induces mitochondrial apoptosis in cisplatin-resistant non-small cell lung cancer cells via suppression of β-catenin/survivin signaling

Matrine is an alkaloid isolated from Sophora flavescens and shows anticancer activities. The present study was carried out to determine the cytotoxic effects of matrine on cisplatin-resistant non-small cell lung cancer (NSCLC) cells and the associated molecular mechanisms. Parental and cisplatin-resistant A549 and H460 NSCLC cells were treated with 1 or 2 g/l of matrine for 48 h, and cell viability and apoptosis were assessed. β-catenin-mediated transcriptional activity, mitochondrial membrane potential (ΔΨm) changes, activation of caspases, and survivin expression were examined. The effect of overexpression of survivin on the anticancer activity of matrine was investigated. Compared to the parental cells, cisplatin-resistant NSCLC cells showed increased β-catenin transcriptional activity. Matrine treatment resulted in a significant reduction in β-catenin activation and survivin expression in the cisplatin-resistant cells. Matrine caused apoptotic death in the cisplatin-resistant NSCLC cells, coupled with loss of ΔΨm and activation of caspase-9 and -3. Matrine-induced apoptosis of the cisplatin-resistant NSCLC cells was significantly reversed by overexpression of survivin. In conclusion, matrine exposure induces mitochondrial apoptosis in cisplatin-resistant NSCLC cells, which is largely mediated through inactivation of β-catenin/survivin signaling. Further investigation of the therapeutic benefit of matrine in overcoming cisplatin resistance in NSCLC is warranted.