miR-200 expression regulates epithelial-to-mesenchymal transition in bladder cancer cells and reverses resistance to epidermal growth factor receptor therapy

Expression profile of microRNA-200 family in hepatocellular carcinoma with bile duct tumor thrombus

OBJECTIVE

The aim of this study was to assess the role of the miR-200 family in the pathogenesis of hepatocellular carcinoma with bile duct tumor thrombus (HCC-BDTT).

BACKGROUND

Hepatocellular carcinoma with bile duct tumor thrombus is a challenging condition because of its rarity and dismal prognosis. Epithelial-to-mesenchymal transition (EMT) is considered a critical step in the progression and metastasis of HCC and is regulated by the microRNA-200 (miR-200) family.

METHODS

Thirty patients with HCC-BDTT were enrolled and 1240 patients with conventional HCC (cHCC) served as clinicopathologic controls. Sixty age- and sex-matched cHCC patients were selected to compare the miR-200 family expression profile and immunohistochemical characteristics. Gain- and loss-of-function studies of the miR-200 family were conducted using the hepatoma cell lines.

RESULTS

Although the mean size of HCC-BDTT was smaller than that of cHCC, the former had a higher incidence of vascular invasion and a poorer long-term survival. The expressions of miR-200c and miR-141 were downregulated in HCC-BDTT (4.5- and 4.8-fold decrease, respectively). Downregulation of both miR-200c and miR-141 independently predicted disease-free survival. The HCC-BDTT, but not cHCC, exhibited overexpression of ZEB1, Twist, transforming growth factor-β receptor type II, and vimentin, and aberrant E-cadherin expression, indicating EMT. The HCC-BDTT demonstrated increased expression in IL-6 and stemness factor Bmi1, but reduced level of metastasis-suppressive protein, insulin-like growth factor-binding protein 4. The invasive ability of the highly aggressive Mahlavu cell was attenuated by pre-miR-200c+141, whereas the invasive ability of the less aggressive Huh7 cell was enhanced by anti-miR-200c+141.

CONCLUSIONS

Simultaneous silencing of miR-200c and miR-141 was likely to be responsible for the development of HCC-BDTT via ZEB1-directed EMT activation and Sec23a-mediated secretome.

Loss of microRNA-200a expression correlates with tumor progression in breast cancer

MicroRNAs (miRNAs) are 19∼22 nucleotide-long, noncoding, small RNAs, involved in post-transcriptional regulation of many target genes. The miRNA-200 family has been shown to play a crucial role in the epithelial to mesenchymal transition in human cancers. In situ hybridization (ISH) was used to investigate the expression level of miRNA-200a in breast cancers. Formalin-fixed, paraffin embedded (FFPE) tissues from normal breast, ductal carcinoma in situ (DCIS), primary cancers, and metastatic lymph nodes were achieved and constructed to tissue microarrays. MiRNA-200a expression was demonstrated in 95.2% of normal breast tissue samples and 80.4% of DCIS, whereas 178 (58.0%) of 307 breast cancers and 83.3% of metastatic lymph node samples lacked miRNA-200a expression (P < 0.001). Moreover, loss of MiRNA-200a expression correlated with high histologic grade (P = 0.017) and perinodal tumor extension (P = 0.026). However, miRNA-200a expression did not predict tumor recurrence or patient survival. In conclusion, loss of miRNA-200a is frequently observed in breast cancers, especially tumors with high grade histology. These findings suggest that miRNA-200a may play an important role in breast cancer initiation and progression. ISH can be used to detect miRNAs in FFPE sections, and should permit the validation of miRNAs as biomarkers in large clinical samples.

Silibinin suppresses EMT-driven erlotinib resistance by reversing the high miR-21/low miR-200c signature in vivo

The flavolignan silibinin was studied for its ability to restore drug sensitivity to EGFR-mutant NSCLC xenografts with epithelial-to-mesenchymal transition (EMT)-driven resistance to erlotinib. As a single agent, silibinin significantly decreased the tumor volumes of erlotinib-refractory NSCLC xenografts by approximately 50%. Furthermore, the complete abrogation of tumor growth was observed with the co-treatment of erlotinib and silibinin. Silibinin fully reversed the EMT-related high miR-21/low miR-200c microRNA signature and repressed the mesenchymal markers SNAIL, ZEB, and N-cadherin observed in erlotinib-refractory tumors. Silibinin was sufficient to fully activate a reciprocal mesenchymal-to-epithelial transition (MET) in erlotinib-refractory cells and prevent the highly migratogenic phenotype of erlotinib-resistant NSCLC cells. Given that the various mechanisms of resistance to erlotinib result from EMT, regardless of the EGFR mutation status, a water-soluble, silibinin-rich milk thistle extract might be a suitable candidate therapy for upcoming clinical trials aimed at preventing or reversing NSCLC progression following erlotinib treatment.

Regulating miRNA by natural agents as a new strategy for cancer treatment

MicroRNAs (miRNAs) are small single-strand non-coding endogenous RNAs that regulate gene expression by multiple mechanisms. Recent evidence suggests that miRNAs are critically involved in the pathogenesis, evolution, and progression of cancer. The miRNAs are also crucial for the regulation of cancer stem cells (CSCs). In addition, miRNAs are known to control the processes of Epithelial-to-Mesenchymal Transition (EMT) of cancer cells. This evidence suggests that miRNAs could serve as targets in cancer treatment, and as such manipulating miRNAs could be useful for the killing CSCs or reversal of EMT phenotype of cancer cells. Hence, targeting miRNAs, which are deregulated in cancer, could be a promising strategy for cancer therapy. Recently, the regulation of miRNAs by natural, nontoxic chemopreventive agents including curcumin, resveratrol, isoflavones, (-)-epigallocatechin-3-gallate (EGCG), lycopene, 3,3'- diindolylmethane (DIM), and indole-3-carbinol (I3C) has been described. Therefore, natural agents could inhibit cancer progression, increase drug sensitivity, reverse EMT, and prevent metastasis though modulation of miRNAs, which will provide a newer therapeutic approach for cancer treatment especially when combined with conventional therapeutics.

MiRNA in melanoma-derived exosomes

Proteins, RNAs and viruses can be spread through exosomes, therefore transport utilizing these nanovesicles is of the great interest. MiRNAs are common exosomal constituents capable of influencing expression of a variety of target genes. MiRNA signatures of exosomes are unique in cancer patients and differ from those in normal controls. The knowledge about miRNA profiles of tumor-derived exosomes may contribute to better diagnosis, determination of tumor progression and response to treatment, as well as to the development of targeted therapies. We summarize the current knowledge with regard to miRNAs that are found in exosomes derived from tumors, particularly from melanoma.

N1-guanyl-1,7-diaminoheptane sensitizes bladder cancer cells to doxorubicin by preventing epithelial-mesenchymal transition through inhibition of eukaryotic translation initiation factor 5A2 activation

Drug resistance greatly reduces the efficacy of doxorubicin-based chemotherapy in bladder cancer treatment; however, the underlying mechanisms are poorly understood. We aimed to investigate whether N1-guanyl-1,7-diaminoheptane (GC7), which inhibits eukaryotic translation initiation factor 5A2 (eIF5A2) activation, exerts synergistic cytotoxicity with doxorubicin in bladder cancer, and whether eIF5A2 is involved in chemoresistance to doxorubicin-based bladder cancer treatment. BIU-87, J82, and UM-UC-3 bladder cancer cells were transfected with eIF5A2 siRNA or negative control siRNA before incubation with doxorubicin alone or doxorubicin plus GC7 for 48 h. Doxorubicin cytotoxicity was enhanced by GC7 in BIU-87, J82, and UM-UC-3 cells. It significantly inhibited activity of eIF5A2, suppressed doxorubicin-induced epithelial-mesenchymal transition in BIU-87 cells, and promoted mesenchymal-epithelial transition in J82 and UM-UC-3 cells. Knockdown of eIF5A2 sensitized bladder cancer cells to doxorubicin, prevented doxorubicin-induced EMT in BIU-87 cells, and encouraged mesenchymal-epithelial transition in J82 and UM-UC-3 cells. Combination therapy with GC7 may enhance the therapeutic efficacy of doxorubicin in bladder cancer by inhibiting eIF5A2 activation and preventing epithelial-mesenchymal transition.

Sequence variation among members of the miR-200 microRNA family is correlated with variation in the ability to induce hallmarks of mesenchymal-epithelial transition in ovarian cancer cells

Background

Epithelial-Mesenchymal Transition (EMT) is a transient and reversible (Mesenchymal-Epithelial Transition or MET) process by which epithelial cells acquire mesenchymal cell characteristics including reduced intercellular adhesion and increased cell motility. While EMT/MET has long been recognized as an essential component of early embryonic development, there is a growing body of evidence indicating that EMT/MET is also a key component of ovarian cancer (OC) metastasis. Recent findings have implicated members of the miR-200 family of microRNAs (miRNAs) in this process.

Methods

Individual members of the miR-200 family of miRNAs were transiently over expressed in metastatic (mesenchymal-like) OC cell lines. Changes in morphology, molecular profiles and drug sensitivity were monitored relative to cells transfected with a negative control.

Results

Morphological hallmarks of MET were detected in cells transfected with all miR-200 family members. Gene expression profiling demonstrated up regulation of epithelial biomarkers and down regulation of mesenchymal biomarkers in transfected cells although significant variation in molecular response and drug sensitivity was associated with different members of the miR-200 family.

Conclusions

Our results indicate that although ectopic overexpression of all members of the miR-200 family in mesenchymal-like OC cells results in morphological changes characteristic of MET, the underlying molecular changes and induced drug sensitivities are highly variable and correlated with sequence variation within the seed and non-seed regions of individual family members.

TGF-β upregulates miR-182 expression to promote gallbladder cancer metastasis by targeting CADM1

Transforming growth factor β (TGF-β) plays important roles in tumor metastasis by regulating miRNAs expression. miR-182 is an important molecule in the regulation of cancer progression. The aim of the study is to assess the role of miR-182 in TGF-β-induced cancer metastasis. In the present study, we found that miR-182 levels are significantly upregulated in GBC tissues compared with normal controls, and miR-182 expression is remarkably increased in primary tumors that subsequently metastasized, when compared to those primary tumors that did not metastasize. TGF-β induces miR-182 expression in GBC cells, and overexpression of miR-182 promotes GBC cell migration and invasion, whereas miR-182 inhibition suppresses TGF-β-induced cancer cell migration and invasion. The blockage of miR-182 by a specific inhibitor effectively inhibits pulmonary metastases in vivo. We further identified that the cell adhesion molecule1 (CADM1) is a new target gene of miR-182. miR-182 negatively regulates CADM1 expression in vitro and in vivo. Importantly, re-expression of CADM1 in GBC cells partially abrogates miR-182-induced cell invasion.

CONCLUSIONS

miR-182 is an important mediator of GBC metastasis, thus offering a new target for the development of therapeutic agents against GBC.

The proto-oncogene KRAS is targeted by miR-200c

The GTPase K-ras is involved in a variety of cellular processes such as differentiation, proliferation and survival. However, activating mutations, which frequently occur in many types of cancer, turn KRAS into one of the most prominent oncogenes. Likewise, miR-200c is a key player in tumorigenesis functioning as a molecular switch between an epithelial, non-migratory, chemosensitive and a mesenchymal, migratory, chemoresistant state. While it has been reported that KRAS is modulated by several tumor suppressor miRNAs, this is the first report on the regulation of KRAS by miR-200c, both playing a pivotal role in oncogenesis. We show that KRAS is a predicted target of miR-200c and that the protein expression of KRAS inversely correlates with the miR-200c expression in a panel of human breast cancer cell lines. KRAS was experimentally validated as a target of miR-200c by Western blot analyses and luciferase reporter assays. Furthermore, the inhibitory effect of miR-200c-dependent KRAS silencing on proliferation and cell cycle was demonstrated in different breast and lung cancer cell lines. Thereby, the particular role of KRAS was dissected from the role of all the other miR-200c targets by specific knockdown experiments using siRNA against KRAS. Cell lines harboring an activating KRAS mutation were similarly affected by miR-200c as well as by the siRNA against KRAS. However, in a cell line with wild-type KRAS only miR-200c was able to change proliferation and cell cycle. Our findings suggest that miR-200c is a potent inhibitor of tumor progression and therapy resistance, by regulating a multitude of oncogenic pathways including the RAS pathway. Thus, miR-200c may cause stronger anti-tumor effects than a specific siRNA against KRAS, emphasizing the potential role of miR-200c as tumor suppressive miRNA.

Integrated mRNA and microRNA transcriptome sequencing characterizes sequence variants and mRNA-microRNA regulatory network in nasopharyngeal carcinoma model systems

Nasopharyngeal carcinoma (NPC) is a prevalent malignancy in Southeast Asia among the Chinese population. Aberrant regulation of transcripts has been implicated in many types of cancers including NPC. Herein, we characterized mRNA and miRNA transcriptomes by RNA sequencing (RNASeq) of NPC model systems. Matched total mRNA and small RNA of undifferentiated Epstein–Barr virus (EBV)-positive NPC xenograft X666 and its derived cell line C666, well-differentiated NPC cell line HK1, and the immortalized nasopharyngeal epithelial cell line NP460 were sequenced by Solexa technology. We found 2812 genes and 149 miRNAs (human and EBV) to be differentially expressed in NP460, HK1, C666 and X666 with RNASeq; 533 miRNA–mRNA target pairs were inversely regulated in the three NPC cell lines compared to NP460. Integrated mRNA/miRNA expression profiling and pathway analysis show extracellular matrix organization, Beta-1 integrin cell surface interactions, and the PI3K/AKT, EGFR, ErbB, and Wnt pathways were potentially deregulated in NPC. Real-time quantitative PCR was performed on selected mRNA/miRNAs in order to validate their expression. Transcript sequence variants such as short insertions and deletions (INDEL), single nucleotide variant (SNV), and isomiRs were characterized in the NPC model systems. A novel TP53 transcript variant was identified in NP460, HK1, and C666. Detection of three previously reported novel EBV-encoded BART miRNAs and their isomiRs were also observed. Meta-analysis of a model system to a clinical system aids the choice of different cell lines in NPC studies. This comprehensive characterization of mRNA and miRNA transcriptomes in NPC cell lines and the xenograft provides insights on miRNA regulation of mRNA and valuable resources on transcript variation and regulation in NPC, which are potentially useful for mechanistic and preclinical studies.

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Using RNASeq we characterized the mRNA and miRNA transcriptomes in NPC and NP models.

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2812 Genes and 149 miRNAs (human and EBV) were differentially expressed in NPC vs NP models.

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533 miRNA–mRNA target pairs were inversely regulated in HK1, C666, and X666 vs NP460.

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ECM, β1 integrin, PI3K/AKT, EGFR, ErbB, and Wnt pathways appeared to be deregulated in NPC.

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A novel TP53 mutation was identified in NP460, HK1, and C666.

Tongxinluo ameliorates renal structure and function by regulating miR-21-induced epithelial-to-mesenchymal transition in diabetic nephropathy

Diabetic nephropathy (DN) is one of the most important diabetic microangiopathies. The epithelial-to-mesenchymal transition (EMT) plays an important role in DN. The physiological role of microRNA-21 (miR-21) was closely linked to EMT. However, it remained elusive whether tongxinluo (TXL) ameliorated renal structure and function by regulating miR-21-induced EMT in DN. This study aimed to determine the effect of TXL on miR-21-induced renal tubular EMT and to explore the relationship between miR-21 and TGF-β1/smads signals. Real-time RT-PCR, cell transfection, in situ hybridization (ISH), and laser confocal microscopy were used, respectively. Here, we revealed that TXL dose dependently lowered miR-21 expression in tissue, serum, and cells. Overexpression of miR-21 can enhance α-smooth muscle actin (SMA) expression and decrease E-cadherin expression by upregulating smad3/p-smad3 expression and downregulating smad7 expression. Interestingly, TXL also increased E-cadherin expression and decreased α-SMA expression by regulating miR-21 expression. More importantly, TXL decreased collagen IV, fibronectin, glomerular basement membrane, glomerular area, and the albumin/creatinine ratio, whereas it increased the creatinine clearance ratio. The results demonstrated that TXL ameliorated renal structure and function by regulating miR-21-induced EMT, which was one of the mechanisms to protect against DN, and that miR-21 may be one of the therapeutic targets for TXL in DN.

Androgen receptor inducing bladder cancer progression by promoting an epithelial-mesenchymal transition

The study investigated the role of androgen receptor (AR) as a potential target for the treatment of bladder cancer in regulating epithelial-mesenchymal transition or transformation (EMT). Cell proliferation, and migration capacity were determined in bladder cancer T24 cells treated with small interfering RNA directed against AR, and expression levels of E-cadherin, β-catenin and N- cadherin were assessed using quantitative reverse transcription PCR (qRT-PCR). Tumour cell growth was evaluated in vivo in T24 tumour-bearing nude mice receiving electroporation-assisted administration of anti-AR small interfering RNA. It was found that low AR expression decreased proliferation and migration of bladder cancer cells. In vivo experiments showed that silencing AR expression significantly suppressed AR-positive bladder tumour growth with decreased cell proliferation. Low AR level of T24 bladder cancer cells treated with dehydrotestosterone (DHT) decreased expression of E-cadherin, β-catenin and N-cadherin expression, indicating a strong sensitivity to the EMT and In cells with low AR content, TGF-β induced down-regulation of E-cadherin and β-catenin. It is concluded that suppression of AR expression decreased the production of TGF-β, inhibiting EMT and bladder cancer cell growth in vitro and in vivo, implying that its use might be a potential therapeutic target for the treatment of bladder cancer.

Expression of miRNAs and ZEB1 and ZEB2 correlates with histopathological grade in papillary urothelial tumors of the urinary bladder

Histopathological grading of papillary urothelial tumors (PUTs) of the urinary bladder is subjective and poorly reproducible. We investigated the relationship between the expression of frequently deregulated microRNAs (miRNAs) as well as their target genes (ZEB1/ZEB2) and bladder cancer histopathological grade in an attempt to find a miRNA that might allow more reliable grading of PUTs. We measured the expression levels of four miRNAs (miR-145, miR-205, miR-125b, and miR-200c) in 120 formalin-fixed, paraffin-embedded bladder tumor tissue samples using real-time PCR assays. ZEB1 and ZEB2 expression was assessed in the same bladder tissues by immunohistochemistry. MiR-205 distinguished low-grade papillary urothelial carcinoma (LG) from high-grade papillary urothelial carcinoma (HG), and miR-145 distinguished HG from infiltrating carcinoma (CA) with an area under the receiver operator characteristic curve (AUC) of 0.992 and 0.997, respectively (sensitivity/specificity of 95.8/96.7 % and 100/91.7 %, respectively; p < 0.05). The expression level of miR-125b was significantly lower in LG than in PUNLMP, with an AUC value of 0.870 (93.3 % sensitivity and 84.2 % specificity; p < 0.05). ZEB1 immunoreactivity was more frequently detected in HG than in LG (57 % vs 13 %, p < 0.01) and in HG than in CA (57 % vs 17 %, p < 0.01). ZEB2 immunoreactivity was more frequent in CA than in HG (83 % vs 54 %, p < 0.05). ZEB1/ZEB2 and miRNAs expression seems to reliably distinguish between different grades of PUTs of the urinary bladder. They might well serve as useful complementary diagnostic biomarkers for grading of papillary urothelial tumors.

Epithelial-mesenchymal Transition and Cell Invasion

Epithelial-mesenchymal transition (EMT) is a complex process in which epithelial cells acquire the characteristics of invasive mesenchymal cells. EMT has been implicated in cancer progression and metastasis as well as the formation of many tissues and organs during development. Epithelial cells undergoing EMT lose cell-cell adhesion structures and polarity, and rearrange their cytoskeletons. Several oncogenic pathways such as transforming growth factor (TGF) -β, Wnt, and Notch signaling pathways, have been shown to induce EMT. These pathways have activated transcription factors including Snail, Slug, and the ZEB family which work as transcriptional repressors of E-cadherin, thereby making epithelial cells motile and resistant to apoptosis. Mounting evidence shows that EMT is associated with cell invasion and tumor progression.In this review, we summarize the characteristic features of EMT, pathways leading to EMT, and the role of EMT in cell invasion. Three topics are addressed in this review: (1) Definition of EMT, (2) Signaling pathways leading to EMT, (3) Role of EMT in cell invasion. Understanding the role of EMT in cell invasion will provide valuable information for establishing strategies to develop anti-metastatic therapeutics which modulate malignant cellular processes mediated by EMT.

MiR-200, a new star miRNA in human cancer

MicroRNAs (miRNAs) are a set of non-coding small RNA molecules in control of gene expression at posttranscriptional/translational level. They not only play crucial roles in normal developmental progress, but also are commonly dysregulated in human diseases, including cancer. MiR-200 is a family of tumor suppressor miRNAs consisting of five members, which are significantly involved in inhibition of epithelial-to-mesenchymal transition (EMT), repression of cancer stem cells (CSCs) self-renewal and differentiation, modulation of cell division and apoptosis, and reversal of chemoresistance. In this article, we summarize the latest findings with regard to the tumor suppressor signatures of miR-200 and the regulatory mechanisms of miR-200 expression. The collected evidence supports that miR-200 is becoming a new star miRNA in study of human cancer.

Altered microRNA expression profile during epithelial wound repair in bronchial epithelial cells

BACKGROUND

Airway epithelial cells provide a protective barrier against environmental particles including potential pathogens. Epithelial repair in response to tissue damage is abnormal in asthmatic airway epithelium in comparison to the repair of normal epithelium after damage. The complex mechanisms coordinating the regulation of the processes involved in wound repair requires the phased expression of networks of genes. Small non-coding RNA molecules termed microRNAs (miRNAs) play a critical role in such coordinated regulation of gene expression. We aimed to establish if the phased expression of specific miRNAs is correlated with the repair of mechanically induced damage to the epithelium.

METHODS

To investigate the possible involvement of miRNA in epithelial repair, we analyzed miRNA expression profiles during epithelial repair in a cell culture model using TaqMan-based quantitative real-time PCR in a TaqMan Low Density Array format. The expression of 754 miRNA genes at seven time points in a 48-hour period during the wound repair process was profiled using the bronchial epithelial cell line 16HBE14o- growing in monolayer.

RESULTS

The expression levels of numerous miRNAs were found to be altered during the wound repair process. These miRNA genes were clustered into 3 different patterns of expression that correlate with the further regulation of several biological pathways involved in wound repair. Moreover, it was observed that expression of some miRNA genes were significantly altered only at one time point, indicating their involvement in a specific stage of the epithelial wound repair.

CONCLUSIONS

In summary, miRNA expression is modulated during the normal repair processes in airway epithelium in vitro suggesting a potential role in regulation of wound repair.

TMPRSS2-ERG gene fusions induce prostate tumorigenesis by modulating microRNA miR-200c

Chromosomal translocations that juxtapose the androgen-sensitive TMPRSS2 gene promoter to the oncogenic ETS-family transcription factor ERG result in excessive ERG overexpression in approximately 50% of prostate cancer (PCa) patients. Although numerous studies have investigated ERG-downstream genes, such studies have not attempted to examine miRNAs, which however are emerging to be important regulators of cancer. Through bioinformatics analysis of ChIP-Seq ERG data and miRNA expression profiling data we nominated miR-200c as a direct target of ERG. Experimentation of PCa cells with ERG overexpression or knockdown demonstrated that ERG directly repressed miR-200c expression by physically binding to the ETS motif within its promoter. Consequently, miR-200c was down-regulated in ERG-positive PCa and miR-200c target gene expression was restored. In addition, the expression pattern of miR-200c target genes predicted ERG status in clinical PCa specimens. Furthermore, miR-200c was found important in modulating ZEB1 up-regulation by ERG. Most importantly, miR-200c reconstitution fully reversed ERG-induced epithelial-to-mesenchymal transition, cell migration and invasion. Therefore, our study report miR-200c as a first miRNA target of ERG and a critical inhibitor of PCa cell motility. Therapeutic delivery of miR-200c may provide personalized treatment for patients with the molecular subtype of PCa that harbors TMPRSS2-ERG gene fusions.

Axl mediates acquired resistance of head and neck cancer cells to the epidermal growth factor receptor inhibitor erlotinib

Elevated expression and activity of the epidermal growth factor receptor (EGFR) is associated with development and progression of head and neck cancer (HNC) and a poor prognosis. Clinical trials with EGFR tyrosine kinase inhibitors (e.g., erlotinib) have been disappointing in HNC. To investigate the mechanisms mediating resistance to these agents, we developed an HNC cell line (HN5-ER) with acquired erlotinib resistance. In contrast to parental HN5 HNC cells, HN5-ER cells exhibited an epithelial-mesenchymal (EMT) phenotype with increased migratory potential, reduced E-cadherin and epithelial-associated microRNAs (miRNA), and elevated vimentin expression. Phosphorylated receptor tyrosine kinase profiling identified Axl activation in HN5-ER cells. Growth and migration of HN5-ER cells were blocked with a specific Axl inhibitor, R428, and R428 resensitized HN5-ER cells to erlotinib. Microarray analysis of HN5-ER cells confirmed the EMT phenotype associated with acquired erlotinib resistance, and identified activation of gene expression associated with cell migration and inflammation pathways. Moreover, increased expression and secretion of interleukin (IL)-6 and IL-8 in HN5-ER cells suggested a role for inflammatory cytokine signaling in EMT and erlotinib resistance. Expression of the tumor suppressor miR-34a was reduced in HN5-ER cells and increasing its expression abrogated Axl expression and reversed erlotinib resistance. Finally, analysis of 302 HNC patients revealed that high tumor Axl mRNA expression was associated with poorer survival (HR = 1.66, P = 0.007). In summary, our results identify Axl as a key mediator of acquired erlotinib resistance in HNC and suggest that therapeutic inhibition of Axl by small molecule drugs or specific miRNAs might overcome anti-EGFR therapy resistance.

miR-200b and cancer/testis antigen CAGE form a feedback loop to regulate the invasion and tumorigenic and angiogenic responses of a cancer cell line to microtubule-targeting drugs

Cancer/testis antigen cancer-associated gene (CAGE) is known to be involved in various cellular processes, such as proliferation, cell motility, and anti-cancer drug resistance. However, the mechanism of the expression regulation of CAGE remains unknown. Target scan analysis predicted the binding of microRNA-200b (miR-200b) to CAGE promoter sequences. The expression of CAGE showed an inverse relationship with miR-200b in various cancer cell lines. miR-200b was shown to bind to the 3'-UTR of CAGE and to regulate the expression of CAGE at the transcriptional level. miR-200b also enhanced the sensitivities to microtubule-targeting drugs in vitro. miR-200b and CAGE showed opposite regulations on invasion potential and responses to microtubule-targeting drugs. Xenograft experiments showed that miR-200b had negative effects on the tumorigenic and metastatic potential of cancer cells. The effect of miR-200b on metastatic potential involved the expression regulation of CAGE by miR-200b. miR-200b decreased the tumorigenic potential of a cancer cell line resistant to microtubule-targeting drugs in a manner associated with the down-regulation of CAGE. ChIP assays showed the direct regulation of miR-200b by CAGE. CAGE enhanced the invasion potential of a cancer cell line stably expressing miR-200b. miR-200b exerted a negative regulation on tumor-induced angiogenesis. The down-regulation of CAGE led to the decreased expression of plasminogen activator inhibitor-1, a TGFβ-responsive protein involved in angiogenesis, and VEGF. CAGE mediated tumor-induced angiogenesis and was necessary for VEGF-promoted angiogenesis. Human recombinant CAGE protein displayed angiogenic potential. Thus, miR-200b and CAGE form a feedback regulatory loop and regulate the response to microtubule-targeting drugs, as well as the invasion, tumorigenic potential, and angiogenic potential.

miR-200b and miR-200c as prognostic factors and mediators of gastric cancer cell progression

PURPOSE

The purpose of this study was to investigate the clinicopathologic significance and potential role of miR-200b and miR-200c in the development and progression of gastric cancer.

EXPERIMENTAL DESIGN

We examined miR-200b and miR-200c expression in 36 paired normal and stomach tumor specimens, as well as gastric cancer cell lines, by quantitative real-time PCR. In addition, miR-200b and miR-200c were detected by ISH using gastric cancer tissue microarrays, and the association between miR-200b and miR-200c levels and clinicopathologic factors and prognosis were analyzed. A luciferase assay was conducted for target evaluation. The functional effects of miR-200b and miR-200c on gastric cancer cells were validated by a cell proliferation assay and cell invasion and migration assays.

RESULTS

miR-200b and miR-200c were downregulated in the gastric cancer specimens and cell lines tested. miR-200b and miR-200c levels were significantly correlated with the clinical stage, T stage, lymph node metastasis, and survival of patients. Ectopic expression of miR-200b and miR-200c impaired cell growth and invasion. In addition, when overexpressed, miR-200b and miR-200c commonly directly targeted DNMT3A, DNMT3B, and SP1 (a transactivator of the DNMT1 gene), which resulted in marked reduction of the expression of DNA methyltransferases DNMT1, DNMT3A, and DNMT3B at the protein level. This effect, in turn, led to a decrease in global DNA methylation and reexpression of p16, RASS1A1, and E-cadherin via promoter DNA hypomethylation.

CONCLUSION

Our findings suggest that miR-200b and miR-200c, as valuable markers of gastric cancer prognosis, may be a promising approach to human gastric cancer treatment.

Role of the epithelial-mesenchymal transition in bladder cancer: from prognosis to therapeutic target

Bladder cancer (BC) is the second most common malignancy of urological organs. However, patients with non-muscle-invasive BC are at high risk of recurrence and progression into muscle-invasive BC, and the prognosis of patients with muscle-invasive BC is limited by the high rate of metastasis. The epithelial-mesenchymal transition (EMT) is characterized by loss of cell-to-cell adhesion and cell polarity and is closely associated with the invasion and metastasis of several cancers. Given the multifocality and high rates of relapse, progression, and metastasis of BC, the EMT is likely to participate in BC as well. Numerous factors associate with the EMT, and the key regulators of the EMT are E-cadherin, N-cadherin, Twist, Snail, Slug, Zeb-1, Zeb-2, vimentin, and microRNAs. This review focuses on the current concepts regarding the EMT in cancer and the evidence for involvement of the EMT in BC. Several potential EMT targets that may be useful in the treatment of BC are also described.

NF-κB-mediated inflammation leading to EMT via miR-200c is involved in cell transformation induced by cigarette smoke extract

Cigarette smoking constitutes a major human health hazard because it is the most important risk factor for lung cancer. Although evidence for smoking-induced lung cancer in humans is strong, the molecular mechanisms by which smoking causes cancer remain to be established. In this investigation, we evaluated the roles of inflammation and the epithelial-mesenchymal transition (EMT) in cigarette smoke extract (CSE)-induced transformation of human bronchial epithelial (HBE) cells. The results showed that chronic exposure to CSE induced EMT and transformation of these cells. Activation of nuclear factor-κB (NF-κB) by CSE increased levels of the proinflammatory interleukin-6 (IL-6), and acute and chronic exposures to CSE caused decreases in miR-200c levels. By blocking NF-κB with Bay11-7082 and IL-6 with anti-IL-6 antibody and enhancement of IL-6 with human recombinant IL-6, we found that the NF-κB signal pathway was involved in CSE-induced increases of IL-6, which suppressed miR-200c expression and promoted EMT. Moreover, IL-6 was necessary for maintenance of CSE-induced transformation and for malignant progression of HBE cells. Finally, blocking of NF-κB with Bay11-7082 prevented CSE-induced EMT and malignant transformation due to decreases of E-cadherin and miR-200c and elevations of IL-6, N-cadherin, and vimentin. Thus, we have defined a link between inflammation and EMT, processes involved in the malignant transformation of cells caused by CSE. This link, mediated through miRNAs, establishes a mechanism for CSE-induced lung carcinogenesis.

A Bmi1-miRNAs cross-talk modulates chemotherapy response to 5-fluorouracil in breast cancer cells

The polycomb group transcriptional modifier Bmi1 is often upregulated in numerous cancers and is intensely involved in normal and cancer stem cells, and importantly is as a prognostic indicator for some cancers, but its role in breast cancer remains unclear. Here, we found Bmi1 overexpression in 5-Fu (5-fluorouracil)-resistant MCF-7 cells (MCF-7/5-Fu) derived from MCF-7 breast cancer cells, MDA-MB-231 and MDA-MB-453 breast cancer cells compared to MCF-7 cells, was related with 5-Fu resistance and enrichment of CD44⁺/CD24^- stem cell subpopulation. Bmi1 knockdown enhanced the sensitivity of breast cancer cells to 5-Fu and 5-Fu induced apoptosis via mitochondrial apoptotic pathway, and decreased the fraction of CD44⁺/CD24^- subpopulation. In addition, our analysis showed inverse expression pattern between Bmi1 and miR-200c and miR-203 in selected breast cancer cell lines, and miR-200c and miR-203 directly repressed Bmi1 expression in protein level confirmed by luciferase reporter assay. MiR-200c and miR-203 overexpression in breast cancer cells downregulated Bmi1 expression accompanied with reversion of resistance to 5-Fu mediated by Bmi1. Inversely, Bmi1 overexpression inhibited miR-200c expression in MCF-7 cells, but not miR-203, however ectopic wild-type p53 expression reversed Bmi1 mediated miR-200c downregulation, suggesting the repressive effect of Bmi1 on miR-200c maybe depend on p53. Thus, our study suggests a cross-talk between Bmi1 and miR-200c mediated by p53, and Bmi1 interference would improve chemotherapy efficiency in breast cancer via susceptive apoptosis induction and cancer stem cell enrichment inhibition.

How microRNAs influence both hereditary and inflammatory-mediated colon cancers

MicroRNAs have emerged as important post-translational regulators of gene expression and are involved in several physiological and pathological states including the pathogenesis of human colon cancers. In regards to tumor development, microRNAs can act as oncogenes or tumor suppressors. Two hereditary predispositions (i.e., Lynch syndrome and familial adenomatous polyposis) contribute to the development of colon cancer. In addition, individuals who suffer from inflammatory bowel diseases such as Crohn's disease or ulcerative colitis have a higher risk of developing colon cancer. Here, we discuss the occurrence of the deregulated expression of microRNAs in colon cancer that arise as a result of hereditary predisposition and inflammatory bowel disease.

Biomarkers in bladder cancer: translational and clinical implications

Bladder cancer is associated with high recurrence and mortality rates. These tumors show vast heterogeneity reflected by diverse morphologic manifestations and various molecular alterations associated with these disease phenotypes. Biomarkers that prospectively evaluate disease aggressiveness, progression risk, probability of recurrence and overall prognosis would improve patient care. Integration of molecular markers with conventional pathologic staging of bladder cancers may refine clinical decision making for the selection of adjuvant and salvage therapy. In the past decade, numerous bladder cancer biomarkers have been identified, including various tumor suppressor genes, oncogenes, growth factors, growth factor receptors, hormone receptors, proliferation and apoptosis markers, cell adhesion molecules, stromal factors, and oncoproteins. Recognition of two distinct pathways for urothelial carcinogenesis represents a major advance in the understanding and management of this disease. Nomograms for combining results from multiple biomarkers have been proposed to increase the accuracy of clinical predictions. The scope of this review is to summarize the major biomarker findings that may have translational and clinical implications.

Krüppel-like factor 8 promotes tumorigenic mammary stem cell induction by targeting miR-146a

The properties of stem cells can be induced during the epithelial to mesenchymal transition (EMT). The responsible molecular mechanisms, however, remain largely undefined. Here we report the identification of the microRNA-146a (miR-146a) as a common target of Krüppel-like factor 8 (KLF8) and TGF-β, both of which are known EMT-inducers. Upon KLF8 overexpression or TGF-β treatment, a significant portion of the MCF-10A cells gained stem cell traits as demonstrated by an increased expression of CD44(high)/CD24low, activity of aldehyde dehydrogenase (ALDH), mammosphere formation and chemoresistance. Along with this change, the expression of miR-146a was highly upregulated in the cells. Importantly, we found that miR-146a was aberrantly co-overexpressed with KLF8 in a panel of invasive human breast cancer cell lines. Ectopic expression of KLF8 failed to induce the stem cell traits in the MCF-10A cells if the cells were pre-treated with miR-146a inhibitor, whereas overexpression of miR-146a in the MCF-10A cells alone was sufficient to induce the stem cell traits. Co-staining and luciferase reporter analyses indicated that miR-146a targets the 3'-UTR of the Notch signaling inhibitor NUMB for translational inhibition. Overexpression of KLF8 dramatically potentiated the tumorigenecity of MCF-10A cells expressing the H-Ras oncogene, which was accompanied by a loss of NUMB expression in the tumors. Taken together, this study identifies a novel role and mechanism for KLF8 in inducing pro-tumorigenic mammary stem cells via miR-146a potentially by activating Notch signaling. This mechanism could be exploited as a therapeutic target against drug resistance of breast cancer.

Alterations of DNA methylome in human bladder cancer

Bladder cancer is the fourth most common cancer in men in the United States, and its recurrence rate is highest among all malignancies. The unmet need for improved strategies for early detection, treatment, and monitoring of the progression of this disease continues to translate into high mortality and morbidity. The quest for advanced diagnostic, therapeutic, and prognostic approaches for bladder cancer is a high priority, which can be achieved by understanding the molecular mechanisms of the initiation and progression of this malignancy. Aberrant DNA methylation in single or multiple cancer-related genes/loci has been found in human bladder tumors and cancer cell lines, and urine sediments, and correlated with many clinicopathological features of this disease, including tumor relapse, muscle-invasiveness, and survival. The present review summarizes the published research on aberrant DNA methylation in connection with human bladder cancer. Representative studies are highlighted to set forth the current state of knowledge, gaps in the knowledgebase, and future directions in this prime epigenetic field of research. Identifying the potentially reversible and 'drugable' aberrant DNA methylation events that initiate and promote bladder cancer development can highlight biological markers for early diagnosis, effective therapy and accurate prognosis of this malignancy.

The evolving understanding of microRNA in bladder cancer

PURPOSE

Micro ribonucleic acid (miR) expression is altered in urologic malignancies, including bladder cancer (BC). Individual miRs have been shown to modulate multiple signaling pathways that contribute to BC. We reviewed the primary literature on the role of miRs in BC; we provide a general introduction to the processing, regulation, and function of miRs as tumor suppressors and oncogenes and critically evaluate the literature on the implications of altered miR expression in BC.

MATERIALS AND METHODS

We searched the English language literature for original and review articles in PubMed from 1993 to March 2013, using the terms "microRNA" and "bladder cancer," "transitional cell carcinoma," or "urothelial carcinoma." This search yielded 133 unique articles with more than 85% of them published within the last 3 years.

RESULTS

To date, the majority of miR studies in BC use profiling to describe dynamic changes in miR expression across stage and grade. Generalized down-regulation of miRs, including those that target the fibroblast growth factor 3 pathway, such as miR-145, miR-101, miR-100, and miR-99a, has been observed in low-grade, non-muscle invasive BC. In contrast, generalized increased expression of miRs is observed in high-grade, muscle-invasive BC compared with adjacent normal bladder urothelium, including miRs predicted to target p53, such as miR-21 and miR-373. Furthermore, p53 suppresses transcriptional factors that promote mesenchymal differentiation, ZEB-1 and ZEB-2, through regulation of the miR200 family.

CONCLUSIONS

Aberrations in miR expression identified between non-muscle invasive BC and muscle-invasive BC provide insight into the molecular alterations known to distinguish the two parallel pathways of bladder carcinogenesis. The heterogeneity of tumor specimens and research methods limits the reproducibility of changes in miR expression profiles between studies and underscores the importance of in vivo validation in a field that utilizes in silico miR target-prediction models.

The relative expression of Mig6 and EGFR is associated with resistance to EGFR kinase inhibitors

The sensitivity of only a few tumors to anti-epidermal growth factor receptor EGFR tyrosine kinase inhibitors (TKIs) can be explained by the presence of EGFR tyrosine kinase (TK) domain mutations. In addition, such mutations were rarely found in tumor types other than lung, such as pancreatic and head and neck cancer. In this study we sought to elucidate mechanisms of resistance to EGFR-targeted therapies in tumors that do not harbor TK sensitizing mutations in order to identify markers capable of guiding the decision to incorporate these drugs into chemotherapeutic regimens. Here we show that EGFR activity was markedly decreased during the evolution of resistance to the EGFR tyrosine kinase inhibitor (TKI) erlotinib, with a concomitant increase of mitogen-inducible gene 6 (Mig6), a negative regulator of EGFR through the upregulation of the PI3K-AKT pathway. EGFR activity, which was more accurately predicted by the ratio of Mig6/EGFR, highly correlated with erlotinib sensitivity in panels of cancer cell lines of different tissue origins. Blinded testing and analysis in a prospectively followed cohort of lung cancer patients treated with gefitinib alone demonstrated higher response rates and a marked increased in progression free survival for patients with a low Mig6/EGFR ratio (approximately 100 days, P = 0.01).

MicroRNA-antagonism regulates breast cancer stemness and metastasis via TET-family-dependent chromatin remodeling

Tumor cells metastasize to distant organs through genetic and epigenetic alterations, including changes in microRNA (miR) expression. Here we find miR-22 triggers epithelial-mesenchymal transition (EMT), enhances invasiveness and promotes metastasis in mouse xenografts. In a conditional mammary gland-specific transgenic (TG) mouse model, we show that miR-22 enhances mammary gland side-branching, expands the stem cell compartment, and promotes tumor development. Critically, miR-22 promotes aggressive metastatic disease in MMTV-miR-22 TG mice, as well as compound MMTV-neu or -PyVT-miR-22 TG mice. We demonstrate that miR-22 exerts its metastatic potential by silencing antimetastatic miR-200 through direct targeting of the TET (Ten eleven translocation) family of methylcytosine dioxygenases, thereby inhibiting demethylation of the mir-200 promoter. Finally, we show that miR-22 overexpression correlates with poor clinical outcomes and silencing of the TET-miR-200 axis in patients. Taken together, our findings implicate miR-22 as a crucial epigenetic modifier and promoter of EMT and breast cancer stemness toward metastasis.

Dysregulation of miR-106a and miR-591 confers paclitaxel resistance to ovarian cancer

Background:

MicroRNAs are noncoding regulatory RNAs strongly implicated in carcinogenesis, cell survival, and chemosensitivity. Here, microRNAs associated with chemoresistance in ovarian carcinoma, the most lethal of gynaecological malignancies, were identified and their functional effects in chemoresistant ovarian cancer cells were assessed.

Methods:

MicroRNA expression in paclitaxel (PTX)-resistant SKpac sublines was compared with that of the PTX-sensitive, parental SKOV3 ovarian cancer cell line using microarray and qRT–PCR. The function of differentially expressed microRNAs in chemoresistant ovarian cancer was further evaluated by apoptosis, cell proliferation, and migration assays.

Results:

Upregulation of miR-106a and downregulation of miR-591 were associated with PTX resistance in ovarian cancer cells and human tumour samples. Transfection with anti-miR-106a or pre-miR-591 resensitized PTX-resistant SKpac cells to PTX by enhancing apoptosis (23 and 42% increase), and inhibited their cell migration (43 and 56% decrease) and proliferation (64 and 65% decrease). Furthermore, ZEB1 was identified as a novel target gene of miR-591, and BCL10 and caspase-7 were target genes of miR-106a, as identified by immunoblotting and luciferase assay.

Conclusion:

MiR-106a and miR-591 have important roles in conferring PTX resistance to ovarian cancer cells. Modulation of these microRNAs resensitizes PTX-resistant cancer cells by targeting BCL10, caspase-7, and ZEB1.

The glioma-associated oncogene homolog 1 promotes epithelial--mesenchymal transition in human esophageal squamous cell cancer by inhibiting E-cadherin via Snail

The glioma-associated oncogene homolog 1 (GLI1) family of zinc finger transcription factors is the nuclear mediator of the Hedgehog pathway that regulates genes essential for various stages of tumor development and progression. However, the role and mechanism by which high expression of GLI1 contributes to the invasion and metastasis of human esophageal squamous cell cancer (ESCC) has not been fully elucidated. In the present study, we demonstrated that GLI1 was over-expressed in human ESCC tissues, especially in ESCC tissues with deep invasion and lymph-node metastasis. Moreover, GLI1 was also over-expressed in ESCC cell lines and correlated with the aggressiveness of ESCC cell lines. In addition, GLI signaling pathway agonist purmorphamine could increase the invasion and metastasis ability of ESCC cells in vitro. There is increasing evidence for the contribution of epithelial-mesenchymal transition (EMT) to ESCC invasion and metastasis, therefore we investigated GLI1's role in EMT. Our results showed that high expression of GLI1 dampened expression of E-cadherin and enhanced the expression of Vimentin, and it also improved the expression of Snail, indicative of its role in EMT occurrence. Mechanistic studies showed that down-expression of Snail reversed GLI1 activation-regulated expression of EMT markers, suggesting the role of Snail in GLI1-mediated EMT. Taken together, our results had revealed that GLI1 could participate in the invasion and metastasis of ESCC through EMT. These studies indicated that in ESCC, GLI1 could be a useful target for cancer prevention and therapy.

MiR-204 down regulates SIRT1 and reverts SIRT1-induced epithelial-mesenchymal transition, anoikis resistance and invasion in gastric cancer cells

BACKGROUND

Our previous studies showed that SIRT1 was over-expressed in gastric cancer specimens and related with lymph node metastasis. However, the mechanism of SIRT1 up-regulation and its association with metastasis in gastric cancer remain unclear. The present study was undertaken to understand the role of microRNA in regulation of SIRT1 in the progression of gastric cancer.

METHODS

Expression of miR-204 and SIRT1 was assessed in two gastric cancer cell lines and 24 matched cancer specimens. Luciferase reporter assay was carried to verify that miR-204 targeting SIRT1. Cell invasion ability of AGS and BGC was detected by transwell invasion assay. Annexin V/PI assay was used to investigate the cell sensitivity of anoikis. Western blot analysis to assess SIRT1, Vimentin, E-Cadherin, LKB1, and β-actin expression was performed in gastic cancer cell lines.

RESULTS

SIRT1 was defined as the target gene and elucidated the biological functions of miR-204 with a luciferase reporter assay and Western blot analysis. We verified that miR-204 levels were down-regulated and significantly associated with the up-regulation of SIRT1 mRNA levels in gastric cancer specimens. Over-expression of miR-204 reduced cell invasion and anoikis resistance in gastric cancer cells. Up-regulation of miR-204 influenced the levels of the epithelial mesenchymal transition (EMT)-associated genes, increasing E-cadherin levels and decreasing Vimentin levels. We demonstrated that the regulation of EMT by miR-204 involves cooperation with LKB1. Furthermore, silencing of SIRT1 phenocopied the effects of miR-204 in gastric cancer cells. These data demonstrate that miR-204 plays an important role in regulating metastasis of gastric cancer, which is involved in post-transcriptional repression of SIRT1.

CONCLUSION

Our results suggest that down-regulation of miR-204 promotes gastric cancer cell invasion by activating the SIRT1-LKB1 pathway. These data demonstrate that miR-204 plays an important role in regulating metastasis of gastric cancer, which is involved in post-transcriptional repression of SIRT1.

Cross-contamination of a UROtsa stock with T24 cells--molecular comparison of different cell lines and stocks

BACKGROUND

UROtsa is an authentic, immortalized human urothelial cell line that is used to study the effects of metals and other toxic substances, mostly in the context of bladder cancer carcinogenesis. Unusual properties on the molecular level of a provided UROtsa cell line stock prompted us to verify its identity.

METHODS

UROtsa cell line stocks from different sources were tested on several molecular levels and compared with other cell lines. MicroRNA and mRNA expression was determined by Real-Time PCR. Chromosome numbers were checked and PCR of different regions of the large T-antigen was performed. DNA methylation of RARB, PGR, RASSF1, CDH1, FHIT, ESR1, C1QTNF6, PTGS2, SOCS3, MGMT, and LINE1 was analyzed by pyrosequencing and compared with results from the cell lines RT4, T24, HeLa, BEAS-2B, and HepG2. Finally, short tandem repeat (STR) profiling was applied.

RESULTS

All tested UROtsa cell line stocks lacked large T-antigen. STR analysis unequivocally identified our main UROtsa stock as the bladder cancer cell line T24, which was different from two authentic UROtsa stocks that served as controls. Analysis of DNA methylation patterns and RNA expression confirmed their differences. Methylation pattern and mRNA expression of the contaminating T24 cell line showed moderate changes even after long-term culture of up to 56 weeks, whereas miRNAs and chromosome numbers varied markedly.

CONCLUSIONS

It is important to check the identity of cell lines, especially those that are not distributed by major cell banks. However, for some cell lines STR profiles are not available. Therefore, new cell lines should either be submitted to cell banks or at least their STR profile determined and published as part of their initial characterization. Our results should help to improve the identification of UROtsa and other cells on different molecular levels and provide information on the use of urothelial cells for long-term experiments.

Reduced expression of miR-200 family members contributes to antiestrogen resistance in LY2 human breast cancer cells

INTRODUCTION

The role of miRNAs in acquired endocrine-resistant breast cancer is not fully understood. One hallmark of tumor progression is epithelial-to-mesenchymal transition (EMT), characterized by a loss of cell adhesion resulting from reduced E-cadherin and increased cell mobility. miR-200 family members regulate EMT by suppressing expression of transcriptional repressors ZEB1/2. Previously we reported that the expression of miR-200a, miR-200b, and miR-200c was lower in LY2 endocrine-resistant, mesenchymal breast cancer cells compared to parental, endocrine sensitive, epithelial MCF-7 breast cancer cells. Here we investigated the regulation of miR-200 family members and their role in endocrine-sensitivity in breast cancer cells.

RESULTS

miR-200 family expression was progressively reduced in a breast cancer cell line model of advancing endocrine/tamoxifen (TAM) resistance. Concomitant with miR-200 decrease, there was an increase in ZEB1 mRNA expression. Overexpression of miR-200b or miR-200c in LY2 cells altered cell morphology to a more epithelial appearance and inhibited cell migration. Further, miR-200b and miR-200c overexpression sensitized LY2 cells to growth inhibition by estrogen receptor (ER) antagonists TAM and fulvestrant. Knockdown of ZEB1 in LY2 cells recapitulated the effect of miR-200b and miR-200c overexpression resulting in inhibition of LY2 cell proliferation by TAM and fulvestrant, but not the aromatase inhibitor exemestane. Demethylating agent 5-aza-2'-deoxycytidine (5-aza-dC) in combination with histone deacetylase inhibitor trichostatin A (TSA) increased miR-200b and miR-200c in LY2 cells. Concomitant with the increase in miR-200b and miR-200c, ZEB1 expression was decreased and cells appeared more epithelial in morphology and were sensitized to TAM and fulvestrant inhibition. Likewise, knockdown of ZEB1 increased antiestrogen sensitivity of LY2 cells resulting in inhibition of cell proliferation.

CONCLUSIONS

Our data indicate that reduced miRNA-200b and miR-200c expression contributes to endocrine resistance in breast cancer cells and that the reduced expression of these miR-200 family members in endocrine-resistant cells can be reversed by 5-aza-dC+TSA.

miRNA expression profiling of 51 human breast cancer cell lines reveals subtype and driver mutation-specific miRNAs

Introduction

Breast cancer is a genetically and phenotypically complex disease. To understand the role of miRNAs in this molecular complexity, we performed miRNA expression analysis in a cohort of molecularly well-characterized human breast cancer cell lines to identify miRNAs associated with the most common molecular subtypes and the most frequent genetic aberrations.

Methods

Using a microarray carrying LNA™ modified oligonucleotide capture probes), expression levels of 725 human miRNAs were measured in 51 breast cancer cell lines. Differential miRNA expression was explored by unsupervised cluster analysis and was then associated with the molecular subtypes and genetic aberrations commonly present in breast cancer.

Results

Unsupervised cluster analysis using the most variably expressed miRNAs divided the 51 breast cancer cell lines into a major and a minor cluster predominantly mirroring the luminal and basal intrinsic subdivision of breast cancer cell lines. One hundred and thirteen miRNAs were differentially expressed between these two main clusters. Forty miRNAs were differentially expressed between basal-like and normal-like/claudin-low cell lines. Within the luminal-group, 39 miRNAs were associated with ERBB2 overexpression and 24 with E-cadherin gene mutations, which are frequent in this subtype of breast cancer cell lines. In contrast, 31 miRNAs were associated with E-cadherin promoter hypermethylation, which, contrary to E-cadherin mutation, is exclusively observed in breast cancer cell lines that are not of luminal origin. Thirty miRNAs were associated with p16^INK4 status while only a few miRNAs were associated with BRCA1, PIK3CA/PTEN and TP53 mutation status. Twelve miRNAs were associated with DNA copy number variation of the respective locus.

Conclusion

Luminal-basal and epithelial-mesenchymal associated miRNAs determine the subdivision of miRNA transcriptome of breast cancer cell lines. Specific sets of miRNAs were associated with ERBB2 overexpression, p16^INK4a or E-cadherin mutation or E-cadherin methylation status, which implies that these miRNAs may contribute to the driver role of these genetic aberrations. Additionally, miRNAs, which are located in a genomic region showing recurrent genetic aberrations, may themselves play a driver role in breast carcinogenesis or contribute to a driver gene in their vicinity. In short, our study provides detailed molecular miRNA portraits of breast cancer cell lines, which can be exploited for functional studies of clinically important miRNAs.

Comparison of non-coding RNAs in human and canine cancer

The discovery of the post-transcriptional gene silencing (PTGS) by small non-protein-coding RNAs is considered as a major breakthrough in biology. In the last decade we just started to realize the biologic function and complexity of gene regulation by small non-coding RNAs. PTGS is a conserved phenomenon which was observed in various species such as fungi, worms, plants, and mammals. Micro RNAs (miRNA) and small interfering RNAs (siRNAs) are two gene silencing mediators constituting an evolutionary conserved class of non-coding RNAs regulating many biological processes in eukaryotes. As this small RNAs appear to regulate gene expression at translational and transcriptional level it is not surprising that during the last decade many human diseases among them Alzheimer's disease, cardiovascular diseases, and various cancer types were associated with deregulated miRNA expression. Consequently small RNAs are considered to hold big promises as therapeutic agents. However, despite of the enormous therapeutic potential many questions remain unanswered. A major critical point, when evaluating novel therapeutic approaches, is the transfer of in vitro settings to an in vivo model. Classical animal models rely on the laboratory kept animals under artificial conditions and often missing an intact immune system. Model organisms with spontaneously occurring tumors as e.g., dogs provide the possibility to evaluate therapeutic agents under the surveillance of an in intact immune system and thereby providing an authentic tumor reacting scenario. Considering the genomic similarity between canines and humans and the advantages of the dog as cancer model system for human neoplasias the analyses of the complex role of small RNAs in canine tumor development could be of major value for both species. Herein we discuss comparatively the role of miRNAs in human and canine cancer development and highlight the potential and advantages of the model organism dog for tumor research.

MicroRNA-200b targets CREB1 and suppresses cell growth in human malignant glioma

MicroRNAs can coordinately repress multiple target genes and interfere with the biological functions of the cell, such as proliferation and apoptosis. In the present study, we report that miR-200b was downregulated in malignant glioma cell lines and specimens. Overexpression of miR-200b suppressed the proliferation and colony formation of glioma cells. An oncogene encoding cAMP responsive element-binding protein 1 (CREB1), which has been shown to be an important transcription factor involved in the proliferation, survival, and metastasis of tumor cells, was here confirmed as a direct target gene of miR-200b. CREB1 was also found to be present at a high level in human glioma tissues. This was inversely correlated with miR-200b expression. Ectopic expression of CREB1 attenuated the growth suppressive phenotypes of glioma cells caused by miR-200b. These results indicate that miR-200b targets the CREB1 gene and suppresses glioma cell growth, suggesting that miR-200b shows tumor-suppressive activity in human malignant glioma.

Association of the epithelial-to-mesenchymal transition phenotype with responsiveness to the p21-activated kinase inhibitor, PF-3758309, in colon cancer models

The p21-activated kinase (PAK) family of serine/threonine kinases, which are overexpressed in several cancer types, are critical mediators of cell survival, motility, mitosis, transcription, and translation. In the study presented here, we utilized a panel of colorectal cancer (CRC) cell lines to identify potential biomarkers of sensitivity or resistance that may be used to individualize therapy to the PAK inhibitor PF-03758309. We observed a wide range of proliferative responses in the CRC cell lines exposed to PF-03758309, this response was recapitulated in other phenotypic assays such as anchorage-independent growth, three-dimensional (3D) tumor spheroid formation, and migration. Interestingly, we observed that cells most sensitive to PF-03758309 exhibited up-regulation of genes associated with a mesenchymal phenotype (CALD1, VIM, ZEB1) and cells more resistant had an up-regulation of genes associated with an epithelial phenotype (CLDN2, CDH1, CLDN3, CDH17) allowing us to derive an epithelial-to-mesenchymal transition (EMT) gene signature for this agent. We assessed the functional role of EMT-associated genes in mediating responsiveness to PF-3758309, by targeting known genes and transcriptional regulators of EMT. We observed that suppression of genes associated with the mesenchymal phenotype conferred resistance to PF-3758309, in vitro and in vivo. These results indicate that PAK inhibition is associated with a unique response phenotype in CRC and that further studies should be conducted to facilitate both patient selection and rational combination strategies with these agents.

Sheep, wolf, or werewolf: cancer stem cells and the epithelial-to-mesenchymal transition

Multiple cancers contain subpopulations that exhibit characteristics of cancer stem cells (CSCs), the ability to self-renew and seed heterogeneous tumors. Recent evidence suggests two potentially overlapping models for these phenotypes: one where stem cells arise from multipotent progenitor cells, and another where they are created via an epithelial to mesenchymal transition. Unraveling this issue is critical, as it underlies phenomena such as metastasis and therapeutic resistance. Therefore, there is intense interest in understanding these two types of CSSs, how they differ from differentiated cancer cells, the mechanisms that drive their phenotypes, and how that knowledge can be incorporated into therapeutics.

MicroRNAs regulate both epithelial-to-mesenchymal transition and cancer stem cells

Concepts and experimental models derived from basic research have been successfully applied to the field of molecular oncology, tremendously increasing our knowledge of the nature and the progression of tumors. The process of epithelial-to-mesenchymal transition, the cancer stem cell hypothesis, and their functional association and interdependence represent some of the most significant examples. The molecular determinants underlying the plasticity of cancers are currently the object of extensive research efforts, and a substantial body of evidence suggests that these models can be connected by the regulatory role of microRNAs, small noncoding RNA molecules with a fundamental role in many cellular functions. This review will highlight and discuss this link and its possible implications for the fight against cancer.

microRNA response elements-regulated TRAIL expression shows specific survival-suppressing activity on bladder cancer

Background

Bladder transitional cell carcinoma greatly threatens human health all over the world. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) shows a strong apoptosis-inducing effect on a variety of cancer cells including bladder cancer. However, adenovirus-mediated TRAIL expression still showed cytotoxicity to normal cells mainly due to lack of tumor specificity.

Methods

To solve the problem, we applied miRNA response elements (MREs) of miR-1, miR-133 and miR-218 to confer TRAIL expression with specificity to bladder cancer cells.

Results

Expression of miR-1, miR-133 and miR-218 was greatly decreased in bladder cancer than normal bladder tissue. Luciferase assay showed that application of the 3 MREs was able to restrain exogenous gene expression to within bladder cancer cells. Subsequently, we constructed a recombinant adenovirus with TRAIL expression regulated by MREs of miR-1, miR-133 and miR-218, namely Ad-TRAIL-MRE-1-133-218. qPCR, immunoblotting and ELISA assays demonstrated that Ad-TRAIL-MRE-1-133-218 expressed in bladder cancer cells, rather than normal bladder cells. The differential TRAIL expression also led to selective apoptosis-inducing and growth-inhibiting effect of Ad-TRAIL-MRE-1-133-218 on bladder cancers. Finally, bladder cancer xenograft in mouse models further confirmed that Ad-TRAIL-MRE-1-133-218 effectively suppressed the growth of bladder cancers.

Conclusions

Collectively, we demonstrated that MREs-based TRAIL delivery into bladder cancer cells was feasible and efficient for cancer gene therapy.

microRNA expression profile in a large series of bladder tumors: identification of a 3-miRNA signature associated with aggressiveness of muscle-invasive bladder cancer

The aim of this study was to evaluate the expression levels of microRNAs (miRNAs) in bladder tumors in order to identify miRNAs involved in bladder carcinogenesis with potential prognostic implications. Expression levels of miRNAs were assessed by quantitative real-time RT-PCR in 11 human normal bladder and 166 bladder tumor samples (86 non-muscle-invasive bladder cancer (NMIBC) and 80 muscle-invasive bladder cancer (MIBC)). The expression level of 804 miRNAs was initially measured in a well-defined series of seven NMIBC, MIBC and normal bladder samples (screening set). The most strongly deregulated miRNAs in tumor samples compared to normal bladder tissue were then selected for RT-PCR validation in a well-characterized independent series of 152 bladder tumors (validation set), and in six bladder cancer cell lines. Expression levels of these miRNAs were tested for their association with clinical outcome. A robust group of 15 miRNAs was found to be significantly deregulated in bladder cancer. Except for two miRNAs, miR-146b and miR-9, which were specifically upregulated in MIBC, the majority of miRNAs (n = 13) were deregulated in the same way in the two types of bladder tumors, irrespective of pathological stage : three miRNAs were upregulated (miR-200b, miR-182 and miR-138) and the other 10 miRNAs were downregulated (miR-1, miR-133a, miR-133b, miR-145, miR-143, miR-204, miR-921, miR-1281, miR-199a and miR-199b). A 3-miRNA signature (miR-9, miR-182 and miR-200b) was found to be related to MIBC tumor aggressiveness and was associated with both recurrence-free and overall survival in univariate analysis with a trend to significance in the multivariate analysis (p = 0.05). Our results suggested a promising individual prognostic value of these new markers.

Bladder cancer: a simple model becomes complex

Bladder cancer is one of the most frequent malignancies in developed countries and it is also characterized by a high number of recurrences. Despite this, several authors in the past reported that only two altered molecular pathways may genetically explain all cases of bladder cancer: one involving the FGFR3 gene, and the other involving the TP53 gene. Mutations in any of these two genes are usually predictive of the malignancy final outcome. This cancer may also be further classified as low-grade tumors, which is always papillary and in most cases superficial, and high-grade tumors, not necessarily papillary and often invasive. This simple way of considering this pathology has strongly changed in the last few years, with the development of genome-wide studies on expression profiling and the discovery of small non-coding RNA affecting gene expression. An easy search in the OMIM (On-line Mendelian Inheritance in Man) database using "bladder cancer" as a query reveals that genes in some way connected to this pathology are approximately 150, and some authors report that altered gene expression (up- or down-regulation) in this disease may involve up to 500 coding sequences for low-grade tumors and up to 2300 for high-grade tumors. In many clinical cases, mutations inside the coding sequences of the above mentioned two genes were not found, but their expression changed; this indicates that also epigenetic modifications may play an important role in its development. Indeed, several reports were published about genome-wide methylation in these neoplastic tissues, and an increasing number of small non-coding RNA are either up- or down-regulated in bladder cancer, indicating that impaired gene expression may also pass through these metabolic pathways. Taken together, these data reveal that bladder cancer is far to be considered a simple model of malignancy. In the present review, we summarize recent progress in the genome-wide analysis of bladder cancer, and analyse non-genetic, genetic and epigenetic factors causing extensive gene mis-regulation in malignant cells.