Cross-talk between MET and EGFR in non-small cell lung cancer involves miR-27a and Sprouty2

Genistein inhibits A549 human lung cancer cell proliferation via miR-27a and MET signaling

Genistein is a soybean isoflavone; in its aglycone it has various biological activities. Animal experiments, clinical studies and epidemiological investigations suggest that genistein has preventative and curative functions for a number of diseases, particularly in cancer. The present study explored the potential anti-cancer effect of genistein by observing its role in inhibiting A549 human lung cancer cell proliferation and investigating the possible mechanism. A549 cells were exposed to various concentrations of genistein (0, 10, 25, 50, 100 and 200 µM; dissolved in physiological saline) for 1, 2 and 3 days. Subsequently, the viability of A549 cells was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, cell apoptosis was examined using a flow cytometer, caspase 3/9 activity was measured using commercial kits, reverse transcription quantitative polymerase chain reaction was used to analyze the miR-27a expression and western blotting was used to investigate MET protein expression. The results suggested a significant inhibition of A549 cell growth following treatment with genistein in a time- and dose-dependent manner. The current study also indicated that treatment with genistein significantly induces cell apoptosis and promotes caspase-3/9 activation of A549 cells in a dose-dependent manner. Further functional assays revealed that the anti-cancer effect of genistein activated microRNA-27a (miR-27a) expression levels and reduced MET protein expression in A549 cells. In conclusion, the present study demonstrates that genistein inhibits A549 human lung cancer cell proliferation. Furthermore, this study reports, for the first time, a correlation between the anti-cancer effect of genistein and miR-27a-mediated MET signaling.

Expression of miR-27a-3p is an independent predictive factor for recurrence in clear cell renal cell carcinoma

MicroRNAs (miRNAs) are noncoding RNAs that regulate gene expression and function in tumor development and progression. We previously identified up-regulated miRNAs in clear cell renal cell carcinoma (ccRCC) compared to matched-pair normal kidney by microarray. Here, we identify miRNAs that are up-regulated in ccRCC and are also correlated with survival and/or recurrence. Twenty-four samples from ccRCC patients who underwent nephrectomies between 2011 and 2012 were divided into two groups: one of eleven patients who experienced recurrence (Group 1), and one of thirteen patients with no evidence of disease (Group 2) 2 years after surgery. Analyzing 22 miRNAs that were up-regulated in ccRCC in our previous study, we identify five miRNAs that were statistically up-regulated in Group 1 versus Group 2 by quantitative real-time PCR. We then evaluated these miRNAs in an independent cohort of 159 frozen ccRCC samples. High levels of miR-27a-3p (p < 0.01) correlated with a worse progression-free survival rate. Multivariate analysis revealed that miR-27a-3p was an independent predictive factor for recurrence. For functional analysis, miR-27a-3p controlled cell proliferation, migration and invasion in RCC cell lines. MiR-27a-3p could act as oncogenic miRNA and may be a candidate for targeted molecular therapy in ccRCC.

miR-27a-3p suppresses tumor metastasis and VM by down-regulating VE-cadherin expression and inhibiting EMT: an essential role for Twist-1 in HCC

Twist-1 and miRNAs have been reported to be associated with tumor metastasis and angiogenesis. However, the relationship between Twist-1 and miRNAs and the function of miRNAs remain largely undefined. We aimed to reveal the Twist-1-related miRNA expression profile and to determine whether Twist-1 functions in tumor metastasis and vasculogenic mimicry (VM) by regulating miRNA expression in hepatocellular carcinoma (HCC). Results showed that the expression of miR-27a-3p was consistently down-regulated in HCC cell lines and tissue samples displaying high expression of Twist-1. Both loss- and gain-of-function assays revealed suppressive effects of miR-27a-3p. Low miR-27a-3p expression was significantly associated with early metastasis in HCC. Subsequent investigations revealed that miR-27a-3p mediated the inhibition of epithelial–mesenchymal transition (EMT). Additional experiments showed that VE-cadherin is a direct target of miR-27a-3p and further demonstrated the critical role of miR-27a-3p in suppressing tumor metastasis and VM. Conclusions: Twist-1 up-regulation in HepG2 cells resulted in the differential expression of 18 miRNAs. Among them, miR-27a-3p deregulation contributed to VM and metastasis. The miR-27a-3p-mediated down-regulation of VE-cadherin and inhibition of EMT may be essential for Twist-1 to induce tumor metastasis and VM. Our findings highlight the importance of miR-27a-3p and suggest a promising new strategy for anti-HCC therapy.

ψ-Bufarenogin, a novel anti-tumor compound, suppresses liver cancer growth by inhibiting receptor tyrosine kinase-mediated signaling

Resistance of hepatocellular carcinoma (HCC) to existing chemotherapeutic agents largely contributes to the poor prognosis of patients, and discovery of novel anti-HCC drug is in an urgent need. Herein we report ψ-Bufarenogin, a novel active compound that we isolated from the extract of toad skin, exhibited potent therapeutic effect in xenografted human hepatoma without notable side effects. In vitro, ψ-Bufarenogin suppressed HCC cells proliferation through impeding cell cycle progression, and it facilitated cell apoptosis by downregulating Mcl-1 expression. Moreover, ψ-Bufarenogin decreased the number of hepatoma stem cells through Sox2 depression and exhibited synergistic effect with conventional chemotherapeutics. Mechanistic study revealed that ψ-Bufarenogin impaired the activation of MEK/ERK pathway, which is essential in the proliferation of hepatoma cells. ψ-Bufarenogin notably suppressed PI3-K/Akt cascade, which was required in ψ-Bufarenogin-mediated reduction of Mcl-1 and Sox2. ψ-Bufarenogin inhibited the auto-phosphorylation and activation of epithelial growth factor receptor (EGFR) and hepatocyte growth factor receptor (c-Met), thereafter suppressed their primary downstream cascades Raf/MEK/ERK and PI3-K/Akt signaling. Taken together, ψ-Bufarenogin suppressed HCC growth via inhibiting, at least partially, receptor tyrosine kinases-regulated signaling, suggesting that ψ-Bufarenogin could be a novel lead compound for anti-HCC drug.

Negative feedback regulation of AXL by miR-34a modulates apoptosis in lung cancer cells

The AXL receptor tyrosine kinase is frequently overexpressed in cancers and is important in cancer invasion/metastasis and chemoresistance. Here, we demonstrate a regulatory feedback loop between AXL and microRNA (miRNA) at the post-transcriptional level. Both the GAS6-binding domain and the kinase domain of AXL, particularly the Y779 tyrosine phosphorylation site, are shown to be crucial for this autoregulation. To clarify the role of miRNAs in this regulation loop, approaches using bioinformatics and molecular techniques were applied, revealing that miR-34a may target the 3' UTR of AXL mRNA to inhibit AXL expression. Interestingly and importantly, AXL overexpression may induce miR-34a expression by activating the transcription factor ELK1 via the JNK signaling pathway. In addition, ectopic overexpression of ELK1 promotes apoptosis through, in part, down-regulation of AXL. Therefore, we propose that AXL is autoregulated by miR-34a in a feedback loop; this may provide a novel opportunity for developing AXL-targeted anticancer therapies.

Early and late effects of prenatal corticosteroid treatment on the microRNA profiles of lung tissue in rats

Glucocorticoids have been administered to mothers at risk of premature delivery to induce maturation of preterm fetal lungs and prevent the development of respiratory distress syndrome. Micro (mi)RNAs serve various crucial functions in cell proliferation, differentiation and organ development; however, few studies have demonstrated an association between miRNAs and lung development. The aim of the present study was to investigate alterations in the miRNA profiles of rat lung tissue following prenatal glucocorticoid therapy for fetal lung development. The differences in miRNA expression profiles were compared between postnatal days 7 (D7) and 120 (D120) rat lung tissues, followed by validation using reverse transcription-quantitative polymerase chain reaction. The miRNA profiles of rat lung tissues following prenatal dexamethasone (DEX) therapy were also investigated. miRNAs with 2-fold changes were selected for further analysis. At D120, 6 upregulated and 6 downregulated miRNAs were detected, compared with D7. Among these differentially expressed miRNAs, miR-101-3p and miR-99b-5p were associated with the lowest and highest expressions of miRNA at D7, respectively. A limited impact on the miRNA profiles of rat lung tissues was observed following prenatal DEX treatment, which may help to further clarify the mechanisms underlying normal lung development. However, the results of the present study cannot entirely elucidate the effects of prenatal DEX treatment on the lung development of premature infants, and further studies investigating the impact of prenatal corticosteroids on fetal lung miRNA profiles are required.

MicroRNAs: Non-coding fine tuners of receptor tyrosine kinase signalling in cancer

Emerging evidence point to a crucial role for non-coding RNAs in modulating homeostatic signaling under physiological and pathological conditions. MicroRNAs, the best-characterized non-coding RNAs to date, can exquisitely integrate spatial and temporal signals in complex networks, thereby confer specificity and sensitivity to tissue response to changes in the microenvironment. MicroRNAs appear as preferential partners for Receptor Tyrosine Kinases (RTKs) in mediating signaling under stress conditions. Stress signaling can be especially relevant to disease. Here we focus on the ability of microRNAs to mediate RTK signaling in cancer, by acting as both tumor suppressors and oncogenes. We will provide a few general examples of microRNAs modulating specific tumorigenic functions downstream of RTK signaling and integrate oncogenic signals from multiple RTKs. A special focus will be devoted to epidermal growth factor receptor (EGFR) signaling, a system offering relatively rich information. We will explore the role of selected microRNAs as bidirectional modulators of EGFR functions in cancer cells. In addition, we will present the emerging evidence for microRNAs being specifically modulated by oncogenic EGFR mutants and we will discuss how this impinges on EGFRmut driven chemoresistance, which fits into the tumor heterogeneity-driven cancer progression. Finally, we discuss how other non-coding RNA species are emerging as important modulators of cancer progression and why the scenario depicted herein is destined to become increasingly complex in the future.

miR-sc8 Inhibits Schwann Cell Proliferation and Migration by Targeting Egfr

MicroRNAs (miRNAs) negatively regulate the expression of target genes at the post-transcriptional level in diverse biological processes. We have previously identified a group of novel miRNAs in proximal nerve following rat sciatic nerve transection by Solexa sequencing. In this study, the biological function and action mode of miR-sc8, one of the above identified miRNAs, were investigated. An increased expression of miR-sc8 inhibited cell proliferation and migration of Schwann cells (SCs), and inversely, silencing of the miR-sc8 expression promoted cell proliferation and migration of SCs. The epidermal growth factor receptor (Egfr) was identified as the target gene of miR-sc8, which exerted negative regulation of Egfr by translational suppression. The temporal change profile of the miR-sc8 expression was negatively correlated with that of the Egfr expression in proximal nerve following sciatic nerve transection. Moreover, Knockdown of Egfr attenuated the promoting effects of miR-sc8 inhibitor on SC proliferation and migration. Overall, our data indicate that miR-sc8 affects phenotype modulation of SCs by targeting Egfr, providing further insights into the regulatory role of miRNAs in peripheral nerve regeneration.

Integrated analysis of the miRNA, gene and pathway regulatory network in gastric cancer

Gastric cancer is one of the most common malignant tumors worldwide; however, the efficacy of clinical treatment is limited. MicroRNAs (miRNAs) are a class of small non-coding RNAs that have been reported to play a key role in the development of cancer. They also provide novel candidates for targeted therapy. To date, in-depth studies on the molecular mechanisms of gastric cancer involving miRNAs are still absent. We previously reported that 5 miRNAs were identified as being significantly increased in gastric cancer, and the role of these miRNAs was investigated in the present study. By using bioinformatics tools, we found that more than 4,000 unique genes are potential downstream targets of gastric cancer miRNAs, and these targets belong to the protein class of nucleic acid binding, transcription factor, enzyme modulator, transferase and receptor. Pathway mapping showed that the targets of gastric cancer miRNAs are involved in the MAPK signaling pathway, pathways in cancer, the PI3K-Akt signaling pathway, the HTLV-1 signaling pathway and Ras signaling pathway, thus regulating cell growth, differentiation, apoptosis and metastasis. Analysis of the pathways related to miRNAs may provides potential drug targets for future therapy of gastric cancer.

Atypical role of sprouty in colorectal cancer: sprouty repression inhibits epithelial-mesenchymal transition

Sprouty (SPRY) appears to act as a tumor suppressor in cancer, whereas we demonstrated that SPRY2 functions as a putative oncogene in colorectal cancer (CRC) (Oncogene, 2010, 29: 5241-5253). We investigated the mechanisms by which SPRY regulates epithelial-mesenchymal transition (EMT) in CRC. SPRY1 and SPRY2 mRNA transcripts were significantly upregulated in human CRC. Suppression of SPRY2 repressed AKT2 and EMT-inducing transcription factors and significantly increased E-cadherin expression. Concurrent downregulation of SPRY1 and SPRY2 also increased E-cadherin and suppressed mesenchymal markers in colon cancer cells. An inverse expression pattern between AKT2 and E-cadherin was established in a human CRC tissue microarray. SPRY2 negatively regulated miR-194-5p that interacts with AKT2 3' untranslated region. Mir-194 mimics increased E-cadherin expression and suppressed cancer cell migration and invasion. By confocal microscopy, we demonstrated redistribution of E-cadherin to plasma membrane in colon cancer cells transfected with miR-194. Spry1(-/-) and Spry2(-/-) double mutant mouse embryonic fibroblasts exhibited decreased cell migration while acquiring several epithelial markers. In CRC, SPRY drive EMT and may serve as a biomarker of poor prognosis.

MicroRNA in Cancer and Cachexia--A Mini-Review

MicroRNAs (miRNAs) are short noncoding RNAs with a length of approximately 22 nucleotides that are involved in posttranscriptional regulation of gene expression. miRNAs cover an important role in all biological processes, and aberrant miRNA expression is commonly associated with cancer. Recent discoveries have associated the involvement of miRNA in an increasingly large number of biological processes, including cachexia. The cachexia syndrome is a debilitating state of cancer that is, at least in part, associated with apoptosis. The mechanism through which tumors promote the characteristic distal loss of muscle and fat mass during the cachectic process is still not deeply investigated. In this review, we briefly describe the role of miRNAs in cancer development and cachexia.

Improved diagnostics targeting c-MET in non-small cell lung cancer: expression, amplification and activation?

BACKGROUND

Several c-MET targeting inhibitory molecules have already shown promising results in the treatment of patients with Non-small Cell Lung Cancer (NSCLC). Combination of EGFR- and c-MET-specific molecules may overcome EGFR tyrosine kinase inhibitor (TKI) resistance. The aim of this study was to allow for the identification of patients who might benefit from TKI treatments targeting MET and to narrow in on the diagnostic assessment of MET.

METHODS

222 tumor tissues of patients with NSCLC were analyzed concerning c-MET expression and activation in terms of phosphorylation (Y1234/1235 and Y1349) using a microarray format employing immunohistochemistry (IHC). Furthermore, protein expression and MET activation was correlated with the amplification status by Fluorescence in Situ Hybridization (FISH).

RESULTS

Correlation was observed between phosphorylation of c-MET at Y1234/1235 and Y1349 (spearman correlation coefficient rs = 0.41; p < 0.0001). No significant correlation was shown between MET expression and phosphorylation (p > 0.05). c-MET gene amplification was detected in eight of 214 patients (3.7%). No significant association was observed between c-MET amplification, c-MET protein expression and phosphorylation.

CONCLUSION

Our data indicate, that neither expression of c-MET nor the gene amplification status might be the best way to select patients for MET targeting therapies, since no correlation with the activation status of MET was observed. We propose to take into account analyzing the phosphorylation status of MET by IHC to select patients for MET targeting therapies. Signaling of the receptor and the activation of downstream molecules might be more crucial for the benefit of therapeutics targeting MET receptor tyrosine kinases than expression levels alone.

Emerging Roles of MicroRNAs in EGFR-Targeted Therapies for Lung Cancer

Lung cancer is a leading cause of cancer mortality worldwide. Several molecular pathways underlying mechanisms of this disease have been partly elucidated, among which the epidermal growth factor receptor (EGFR) pathway is one of the well-known signaling cascades that plays a critical role in tumorigenesis. Dysregulation of the EGFR signaling is frequently found in lung cancer. The strategies to effectively inhibit EGFR signaling pathway have been mounted for developing anticancer therapeutic agents. However, most anti-EGFR-targeted agents fail to repress cancer progression because of developing drug-resistance. Therefore, studies of the mechanisms underpinning the resistance toward anti-EGFR agents may provide important findings for lung cancer treatment using anti-EGFR therapies. Recently, increasing numbers of miRNAs are correlated with the drug resistance of lung cancer cells to anti-EGFR agents, indicating that miRNAs may serve as novel targets and/or promising predictive biomarkers for anti-EGFR therapy. In this paper, we summarize the emerging role of miRNAs as regulators to modulate the EGFR signaling and the resistance of lung cancer cells to anti-EGFR therapy. We also highlight the evidence supporting the use of miRNAs as biomarkers for response to anti-EGFR agents and as novel therapeutic targets to circumvent the resistance of lung cancer cells to EGFR inhibitors.

Ginsenoside-Rg1 induces angiogenesis by the inverse regulation of MET tyrosine kinase receptor expression through miR-23a

Therapeutic angiogenesis has been implicated in ischemic diseases and wound healing. Ginsenoside-Rg1 (Rg1), one of the most abundant active components of ginseng, has been demonstrated as an angiogenesis-stimulating compound in different models. There is increasing evidence implicating microRNAs (miRNAs), a group of non-coding RNAs, as important regulators of angiogenesis, but the role of microRNAs in Rg1-induced angiogenesis has not been fully explored. In this report, we found that stimulating endothelial cells with Rg1 could reduce miR-23a expression. In silico experiments predicted hepatocyte growth factor receptor (MET), a well-established mediator of angiogenesis, as the target of miR-23a. Transfection of the miR-23a precursor or inhibitor oligonucleotides validated the inverse relationship of miR-23a and MET expression. Luciferase reporter assays further confirmed the interaction between miR-23a and the MET mRNA 3'-UTR. Intriguingly, ginsenoside-Rg1 was found to increase MET protein expression in a time-dependent manner. We further demonstrated that ginsenoside-Rg1-induced angiogenic activities were indeed mediated through the down-regulation of miR-23a and subsequent up-regulation of MET protein expression, as confirmed by gain- and loss-of-function angiogenic experiments. In summary, our results demonstrated that ginsenoside-Rg1 could induce angiogenesis by the inverse regulation of MET tyrosine kinase receptor expression through miR-23a. This study has broadened our understanding of the non-genomic effects of ginsenoside-Rg1, and provided molecular evidence that warrant further development of natural compound as novel angiogenesis-promoting therapy.

Dysregulation of the Met pathway in non-small cell lung cancer: implications for drug targeting and resistance

The receptor tyrosine kinase, Met, orchestrates a complex signalling network that physiologically drives a programme of 'invasive growth'. In cancer however, this process may be co-opted to promote proliferation, survival and metastasis of cancer cells. Met is thus a key therapeutic target, not least in non-small cell lung cancer (NSCLC) where it is one of the most commonly dysregulated driver oncogenes. Identifying robust biomarkers that allow the selection of patients most likely to respond to Met targeted therapies will however be essential to realising their potential. This has been underlined recently by the early termination of three pivotal phase III trials investigating Met targeted agents in NSCLC, all of which failed to show clinical benefit. In contrast to these trials, which were relatively unselective, a couple of early phase trials have recently been instigated that select patients on the basis of Met amplification. While still at an early stage, interim results are relatively encouraging and strengthen the rationale for using Met amplifaction as a biomarker. Here we will discuss this and other aberrations in Met signalling in relation to their significance in the therapeutic targeting of Met.

miR-27 is associated with chemoresistance in esophageal cancer through transformation of normal fibroblasts to cancer-associated fibroblasts

There is increasing evidence that the expression of microRNA (miRNA) in cancer is associated with chemosensitivity but the mechanism of miRNA-induced chemoresistance has not been fully elucidated. The aim of this study was to examine the role of extracellular miRNA in the response to chemotherapy in esophageal cancer. First, serum expression of miRNAs selected by miRNA array was measured by quantitative reverse transcription-polymerase chain reaction in 68 patients with esophageal cancer who received cisplatin-based chemotherapy to examine the relationship between miRNA expression and response to chemotherapy. The serum expression levels of 18 miRNAs were different between responders and non-responders by miRNA array. Of these, high expression levels of miR-27a/b correlated with poor response to chemotherapy in patients with esophageal cancer. Next, in vitro assays were conducted to investigate the mechanism of miRNA-induced chemoresistance. Although transfection of miR-27a/b to cancer cells had no significant impact on chemosensitivity, esophageal cancer cells cultured in supernatant of miR-27a/b-transfected normal fibroblast showed reduced chemosensitivity to cisplatin, compared with cancer cells cultured in supernatant of normal fibroblast. MiR-27a/b-transfected normal fibroblast showed α-smooth muscle actin (α-SMA) expression, a marker of cancer-associated fibroblasts (CAF) and increased production of transforming growth factor-β (TGF-β). Chemosensitivity recovered after administration of neutralizing antibody of TGF-β to the supernatant transfer experiments. Our results indicated that miR-27a/b is involved in resistance to chemotherapy in esophageal cancer, through miR-27a/b-induced transformation of normal fibroblast into CAF.

The EGFR/ErbB3 Pathway Acts as a Compensatory Survival Mechanism upon c-Met Inhibition in Human c-Met+ Hepatocellular Carcinoma

Background

c-Met, a high-affinity receptor for Hepatocyte Growth Factor (HGF), plays a critical role in tumor growth, invasion, and metastasis. Hepatocellular carcinoma (HCC) patients with activated HGF/c-Met signaling have a significantly worse prognosis. Targeted therapies using c-Met tyrosine kinase inhibitors are currently in clinical trials for HCC, although receptor tyrosine kinase inhibition in other cancers has demonstrated early success. Unfortunately, therapeutic effect is frequently not durable due to acquired resistance.

Methods

We utilized the human MHCC97-H c-Met positive (c-Met⁺) HCC cell line to explore the compensatory survival mechanisms that are acquired after c-Met inhibition. MHCC97-H cells with stable c-Met knockdown (MHCC97-H c-Met KD cells) were generated using a c-Met shRNA vector with puromycin selection and stably transfected scrambled shRNA as a control. Gene expression profiling was conducted, and protein expression was analyzed to characterize MHCC97-H cells after blockade of the c-Met oncogene. A high-throughput siRNA screen was performed to find putative compensatory survival proteins, which could drive HCC growth in the absence of c-Met. Findings from this screen were validated through subsequent analyses.

Results

We have previously demonstrated that treatment of MHCC97-H cells with a c-Met inhibitor, PHA665752, results in stasis of tumor growth in vivo. MHCC97-H c-Met KD cells demonstrate slower growth kinetics, similar to c-Met inhibitor treated tumors. Using gene expression profiling and siRNA screening against 873 kinases and phosphatases, we identified ErbB3 and TGF-α as compensatory survival factors that are upregulated after c-Met inhibition. Suppressing these factors in c-Met KD MHCC97-H cells suppresses tumor growth in vitro. In addition, we found that the PI3K/Akt signaling pathway serves as a negative feedback signal responsible for the ErbB3 upregulation after c-Met inhibition. Furthermore, in vitro studies demonstrate that combination therapy with PHA665752 and Gefitinib (an EGFR inhibitor) significantly reduced cell viability and increased apoptosis compared with either PHA665752 or Gefitinib treatment alone.

Conclusion

c-Met inhibition monotherapy is not sufficient to eliminate c-Met⁺ HCC tumor growth. Inhibition of both c-Met and EGFR oncogenic pathways provides superior suppression of HCC tumor growth. Thus, combination of c-Met and EGFR inhibition may represent a superior therapeutic regimen for c-Met⁺ HCC.

MicroRNA and MET in lung cancer

MicroRNAs (miRNAs) are a class of small non-protein coding RNAs that modulate important cellular functions via their post-transcriptional regulation of messenger RNAs (mRNAs). Recent evidences from multiple tumor types and model systems implicate miRNA dysregulation as a common mechanism of tumorigenesis, cancer progression and resistance to therapy. Several miRNAs are dysregulated in cancers and a single miRNA can have multiple targets involved in different oncogenic pathways. MET, the tyrosine kinase receptor for hepatocyte growth factor (HGF), has a central role in lung cancer development and in acquired resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors; it has been predicted and shown to be the target gene of multiple miRNAs, which play a crucial role in controlling its activity in a stimulatory or inhibitory sense. In this review we will focus on the most important and recent studies about the role of miRNAs in the control of MET expression, reporting also the progress made using miRNAs for therapy of lung cancer.

MET/HGF pathway in multiple myeloma: from diagnosis to targeted therapy?

The interaction between neoplastic cells and the microenvironment is critical in several cancers and plays a central role in multiple myeloma. Microenvironmental stimuli support plasma cell proliferation, survival, motility and can determine drug resistance. The network between plasma cells and surrounding cells is also responsible for increasing angiogenesis, unbalancing bone formation and bony lesions. The MET/HGF pathway is a key player in this interaction and has been found to be abnormally active in both malignant plasma cells and surrounding cells. Patients with abnormal MET and/or HGF levels usually have a poor outcome even when treated with novel drugs. This review addresses the role of MET/HGF in the pathogenesis of myeloma and describes the role of MET/HGF signaling as a prognostic factor. The different techniques to detect MET/HGF abnormalities are examined and a description of compounds targeting MET/HGF is also provided.

Adipose tissue-secreted miR-27a promotes liver cancer by targeting FOXO1 in obese individuals

The current notion that obesity is a major risk factor for the development of and the mortality associated with a subset of liver cancer is well appreciated. However, detailed mechanistic insights underlying this relationship are lacking. Better understanding of the adipose tissue-secreted miRNAs that play a potential role in defining primary liver cancer development and mediating the obesity-cancer communication offers the potential for new insights into tumor growth and interventions to modulate tumor formation and progression. In this study, we clearly demonstrated that miR-27a is more highly upregulated in cancer, plasma, and adipose samples from obese liver cancer cases, and therefore reasoned that miR-27a excreted from adipose tissue leads to liver cancer development. To address this idea, we prepared miR-27a-overexpressing 3T3-L1 adipocytes and cocultured them with HepG2 liver cancer cells. Our results demonstrated that secretory miR-27a promoted liver cancer cell proliferation through the downregulation of the transcription factor FOXO1 and promoted the G1/S cell cycle transition by decreasing the cell cycle inhibitors p21 and p27 and increasing the cell cycle regulator cyclin D1. These findings improve our understanding of the involvement of miR-27a in obesity-liver cancer communication and might provide a novel putative target for obesity-driven primary liver cancer diagnosis and therapy.

Alcohol-induced miR-27a regulates differentiation and M2 macrophage polarization of normal human monocytes

Alcohol abuse is a leading cause of liver disease characterized by liver inflammation, fatty liver, alcoholic hepatitis, or liver cirrhosis. Immunomodulatory effects of alcohol on monocytes and macrophages contribute to alcoholic liver disease. Alcohol use, an independent risk factor for progression of hepatitis C virus (HCV) infection-mediated liver disease, impairs host defense and alters cytokine production and monocyte/macrophage activation. We hypothesized that alcohol and HCV have synergistic effects on the phenotype and function of monocytes. Our data show that acute alcohol binge drinking in healthy volunteers results in increased frequency of CD16(+) and CD68(+) and M2-type (CD206(+), dendritic cell [DC]-SIGN(+)-expressing and IL-10-secreting) circulating CD14(+) monocytes. Expression of HCV-induced CD68 and M2 markers (CD206 and DC-SIGN) in normal monocytes was further enhanced in the presence of alcohol. The levels of microRNA (miR)-27a was significantly upregulated in monocytes cultured in the presence of alcohol or alcohol and HCV as compared with HCV alone. The functional role of miR-27a in macrophage polarization was demonstrated by transfecting monocytes with an miR-27a inhibitor that resulted in reduced alcohol- and HCV- mediated monocyte activation (CD14 and CD68 expression), polarization (CD206 and DC-SIGN expression), and IL-10 secretion. Overexpression of miR-27a in monocytes enhanced IL-10 secretion via activation of the ERK signaling pathway. We found that miR-27a promoted ERK phosphorylation by downregulating the expression of ERK inhibitor sprouty2 in monocytes. Thus, we identified that sprouty2 is a target of miR-27a in human monocytes. In summary, our study demonstrates the regulatory role of miR-27a in alcohol-induced monocyte activation and polarization.

Pathway crosstalk analysis of non-small cell lung cancer based on microarray gene expression profiling

AIMS AND BACKGROUND

Lung cancer is characterized by uncontrolled cell growth in the lung tissue. A major challenge in cancer research is the biological interpretation of the complexity of cancer somatic mutation profiles. This study examines the role of pathway crosstalk in the metastatic process of lung cancer cells based on DNA microarray analysis.

METHODS

We downloaded the gene expression profile GSE10096 from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) were identified and the gene functions of selected DEGs were further analyzed. After KEGG pathway analysis, dysfunctional pathways and dysfunctional crosstalk between pathways in two types of lung cancer cells (low metastasis, M1, and high metastasis, M5) were examined.

RESULTS

A total of 13433 genes were filtered as DEGs, and after pathway analysis, 108 signaling pathways related to cancer signaling pathways were screened, including a host pathway hsa05223 and 79 neighbor pathways. Dysfunctional crosstalk analysis of pathways revealed that pathway crosstalk dysfunction of M1 and M5 cells mainly occurred between hsa05223 (non-small cell lung cancer) and hsa04310 (Wnt signaling pathway), and between non-small cell lung cancer and hsa04520 (adherens junction), respectively. Significant pathway crosstalk dysfunction also existed between adherens junction and other classical signaling pathways such as hsa04110 (cell cycle), hsa04310 (Wnt signaling pathway), hsa04350 (TGF-beta signaling pathway), and hsa04630 (Jak-STAT signaling pathway).

CONCLUSIONS

Our discovery will help to elucidate the molecular mechanisms of the high carcinogenic and metastatic potential of lung cancer cells. In addition, it will pave the way to developing effective therapies for lung cancer.

c-Met and Other Cell Surface Molecules: Interaction, Activation and Functional Consequences

The c-Met receptor, also known as the HGF receptor, is one of the most studied tyrosine kinase receptors, yet its biological functions and activation mechanisms are still not fully understood. c-Met has been implicated in embryonic development and organogenesis, in tissue remodelling homeostasis and repair and in cancer metastasis. These functions are indicative of the many cellular processes in which the receptor plays a role, including cell motility, scattering, survival and proliferation. In the context of malignancy, sustained activation of c-Met leads to a signalling cascade involving a multitude of kinases that initiate an invasive and metastatic program. Many proteins can affect the activation of c-Met, including a variety of other cell surface and membrane-spanning molecules or receptors. Some cell surface molecules share structural homology with the c-Met extracellular domain and can activate c-Met via clustering through this domain (e.g., plexins), whereas other receptor tyrosine kinases can enhance c-Met activation and signalling through intracellular signalling cascades (e.g., EGFR). In this review, we provide an overview of c-Met interactions and crosstalk with partner molecules and the functional consequences of these interactions on c-Met activation and downstream signalling, c-Met intracellular localization/recycling and c-Met degradation.

Aberrant regulation of FBW7 in cancer

FBW7 (F-box and WD repeat domain-containing 7) or Fbxw7 is a tumor suppressor, which promotes the ubiquitination and subsequent degradation of numerous oncoproteins including Mcl-1, Cyclin E, Notch, c- Jun, and c-Myc. In turn, FBW7 is regulated by multiple upstream factors including p53, C/EBP-δ, EBP2, Pin1, Hes-5 and Numb4 as well as by microRNAs such as miR-223, miR-27a, miR-25, and miR-129-5p. Given that the Fbw7 tumor suppressor is frequently inactivated or deleted in various human cancers, targeting FBW7 regulators is a promising anti-cancer therapeutic strategy.

c-Met and miRs in Cancer

c-Met, a member of the receptor tyrosine kinase family, is involved in a wide range of cellular processes, including tumor survival, cell growth, angiogenesis and metastasis, and resulting in overexpression in many human cancers, leading to a constitutive activation of the downstream pathways. Recently identified MicroRNAs are a family of small noncoding RNA molecules, extensively studied in cancer, that exert their action by inhibiting gene expression at the posttranscriptional level in several biological processes. Aberrant regulation of microRNAs expression has been implicated in the pathogenesis of different human neoplasia. Several publications point out the connections between c-Met and its ligand hepatocyte growth factor (HGF) and microRNAs. This review summarizes the current knowledge about the interplay between c-Met/HGF and microRNAs and provides evidence that microRNAs are a novel and additional system to regulate c-Met expression in tumors. In the future, microRNAs connected to c-Met may provide an additional option to inhibiting this oncogene from orchestrating an invasive growth program.

Curcumin inhibits proliferation–migration of NSCLC by steering crosstalk between a Wnt signaling pathway and an adherens junction via EGR-1

Crosstalk between Wnt pathways and adherens junction is associated with NSCLC. Curcumin blocks cell proliferation and migration in non-small cell cancer by regulating EGR-1.

Tumor-suppressive microRNA-206 as a dual inhibitor of MET and EGFR oncogenic signaling in lung squamous cell carcinoma

Expression of the oncogene hepatocyte growth factor receptor (MET) and phosphorylation of the MET protein have been associated with both primary and acquired resistance to tyrosine kinase inhibitors (TKIs) used in therapy targeting the epidermal growth factor receptor (EGFR) in patients with non-small cell lung cancers (NSCLCs). Therefore, simultaneous inhibition of both of these receptor tyrosine kinases (RTKs) should improve disease treatment. Our previous study of microRNA (miRNA) expression signatures of lung squamous cell carcinoma (lung-SCC) revealed that microRNA-206 (miR‑206) was significantly reduced in lung-SCC tissues, suggesting that miR‑206 functions as a tumor suppressor in the disease. Furthermore, putative miR‑206 binding sites were annotated in the 3'-UTRs of MET and EGFR RTKs in miRNA databases. The aim of the study was to investigate the functional significance of miR‑206 in lung-SCC and to confirm the inhibition of both MET and EGFR oncogenic signaling by expression of miR‑206 in cancer cells. We found that restoration of mature miR‑206 inhibited cancer cell proliferation, migration, and invasion in EBC-1 cells through downregulation of both mRNA and protein levels of MET and EGFR. Interestingly, phosphorylation of ERK1/2 and AKT signaling were inhibited by restoration of miR‑206 in cancer cells. Overexpression of MET and EGFR were observed in clinical specimens of lung-SCC. Tumor-suppressive miR‑206 inhibited dual signaling networks activated by MET and EGFR, and these findings will provide new insights into the novel molecular mechanisms of lung-SCC oncogenesis and new therapeutic approaches for the treatment of this disease.

A comprehensive transcriptional portrait of human cancer cell lines

Tumor-derived cell lines have served as vital models to advance our understanding of oncogene function and therapeutic responses. Although substantial effort has been made to define the genomic constitution of cancer cell line panels, the transcriptome remains understudied. Here we describe RNA sequencing and single-nucleotide polymorphism (SNP) array analysis of 675 human cancer cell lines. We report comprehensive analyses of transcriptome features including gene expression, mutations, gene fusions and expression of non-human sequences. Of the 2,200 gene fusions catalogued, 1,435 consist of genes not previously found in fusions, providing many leads for further investigation. We combine multiple genome and transcriptome features in a pathway-based approach to enhance prediction of response to targeted therapeutics. Our results provide a valuable resource for studies that use cancer cell lines.

Dual regulation of receptor tyrosine kinase genes EGFR and c-Met by the tumor-suppressive microRNA-23b/27b cluster in bladder cancer

Recent clinical trials of chemotherapeutics for advanced bladder cancer (BC) have shown limited benefits. Therefore, new prognostic markers and more effective treatment strategies are required. One approach to achieve these goals is through the analysis of RNA networks. Our recent studies of microRNA (miRNA) expression signatures revealed that the microRNA-23b/27b (miR-23b/27b) cluster is frequently downregulated in various types of human cancers. However, the functional role of the miR-23b/27b cluster in BC cells is still unknown. Thus, the aim of the present study was to investigate the functional significance of the miR-23b/27b cluster and its regulated molecular targets, with an emphasis on its contributions to BC oncogenesis and metastasis. The expression levels of the miR-23b/27b cluster were significantly reduced in BC clinical specimens. Restoration of mature miR-23b or miR-27b miRNAs significantly inhibited cancer cell migration and invasion, suggesting that these clustered miRNAs function as tumor suppressors. Gene expression data and in silico analysis demonstrated that the genes coding for the epidermal growth factor receptor (EGFR) and hepatocyte growth factor receptor (c-Met) were potential targets of the miR-23b/27b cluster. Luciferase reporter assays and western blotting demonstrated that EGFR and c-Met receptor trypsine kinases were directly regulated by these clustered miRNAs. We conclude that the decreased expression of the tumor-suppressive miR-23b/27b cluster enhanced cancer cell proliferation, migration and invasion in BC through direct regulation of EGFR and c-Met signaling pathways. Our data on RNA networks regulated by tumor-suppressive miR-23b/27b provide new insights into the potential mechanisms of BC oncogenesis and metastasis.

Functional study of miR-27a in human hepatic stellate cells by proteomic analysis: comprehensive view and a role in myogenic tans-differentiation

We previous reported that miR-27a regulates lipid metabolism and cell proliferation during hepatic stellate cells (HSCs) activation. To further explore the biological function and underlying mechanisms of miR-27a in HSCs, global protein expression affected by overexpression of miR-27a in HSCs was analyzed by a cleavable isotope-coded affinity tags (cICAT) based comparative proteomic approach. In the present study, 1267 non-redundant proteins were identified with unique accession numbers (score ≥1.3, i.e. confidence ≥95%), among which 1171 were quantified and 149 proteins (12.72%) were differentially expressed with a differential expression ratio of 1.5. We found that up-regulated proteins by miR-27a mainly participate in cell proliferation and myogenesis, while down-regulated proteins were the key enzymes involved in de novo lipid synthesis. The expression of a group of six miR-27a regulated proteins was validated and the function of one miR-27a regulated protein was further validated. The results not only delineated the underlying mechanism of miR-27a in modulating fat metabolism and cell proliferation, but also revealed a novel role of miR-27a in promoting myogenic tans-differentiation during HSCs activation. This study also exemplified proteomics strategy as a powerful tool for the functional study of miRNA.

MicroRNA and cancer--a brief overview

MicroRNAs (miRNAs) are short non-coding RNAs with a length of ∼22 nucleotides, involved in posttranscriptional regulation of gene expression. Until now, over 2588 miRNAs have been identified in humans and the list is growing. MicroRNAs have an important role in all biological processes and aberrant miRNA expression is associated with many diseases including cancer. In the year 2002 the first connection between cancer and miRNA deregulation was discovered. Since then, a lot of information about the key role which miRNAs play in cancer development and drug resistance has been gained. However, there is still a long way to go to fully understand the miRNA world. In this review, we briefly describe miRNA biogenesis and discuss the role of miRNAs in cancer development and drug resistance. Finally we explain how miRNAs can be used as biomarkers and as a novel therapeutic approach in cancer.

Emerging role of MicroRNAs and long noncoding RNAs in respiratory disease

The advent of techniques such as microarrays and high-throughput sequencing has revolutionized our ability to examine messenger RNA (mRNA) expression within the respiratory system. Importantly, these approaches have also uncovered the widespread expression of "noncoding RNAs," including microRNAs and long noncoding RNAs, which impact biologic responses through the regulation of mRNA transcription and/or translation. To date, most studies of the role of noncoding RNAs have focused on microRNAs, which regulate mRNA translation via the RNA interference pathway. These studies have shown changes in microRNA expression in cells and tissues derived from patients with asthma, pulmonary fibrosis, cystic fibrosis, COPD, and non-small cell lung cancer. Although the evidence is currently limited, we review the work that has been carried out in cell and animal models that has identified the function and mechanism of action of a small number of these microRNAs in disease etiology. In addition to microRNAs, we assess the emerging evidence that long noncoding RNAs regulate respiratory phenotype. Because these investigations into long noncoding RNAs were performed almost exclusively in non-small cell lung cancer, future work will need to extend these into other respiratory diseases and to analyze how microRNAs and long noncoding RNAs interact to regulate mRNA expression. From a clinical perspective, the targeting of noncoding RNAs as a novel therapeutic approach will require a deeper understanding of their function and mechanism of action. However, in the short term, changes in miRNA and long noncoding RNA expression are likely to be of use as biomarkers for disease stratification and/or assessment of drug action.

Crosstalk between kinases, phosphatases and miRNAs in cancer

Reversible phosphorylation of proteins, performed by kinases and phosphatases, is the major post translational protein modification in eukaryotic cells. This intracellular event represents a critical regulatory mechanism of several signaling pathways and can be related to a vast array of diseases, including cancer. Cancer research has produced increasing evidence that kinase and phosphatase activity can be compromised by mutations and also by miRNA silencing, performed by small non-coding and endogenously produced RNA molecules that lead to translational repression. miRNAs are believed to target about one-third of human mRNAs while a single miRNA may target about 200 transcripts simultaneously. Regulation of the phosphorylation balance by miRNAs has been a topic of intense research over the last years, spanning topics going as far as cancer aggressiveness and chemotherapy resistance. By addressing recent studies that have shown miRNA expression patterns as phenotypic signatures of cancers and how miRNA influence cellular processes such as apoptosis, cell cycle control, angiogenesis, inflammation and DNA repair, we discuss how kinases, phosphatases and miRNAs cooperatively act in cancer biology.

MicroRNAs in Cancer Biology and Therapy: Current Status and Perspectives

The study of a class of small non-coding RNA molecules, named microRNAs (miRNAs), has advanced our understanding of many of the fundamental processes of cancer biology and the molecular mechanisms underlying tumor initiation and progression. MiRNA research has become more and more attractive as evidence is emerging that miRNAs likely play important regulatory roles virtually in all essential bioprocesses. Looking at this field over the past decade it becomes evident that our understanding of miRNAs remains rather incomplete. As research continues to reveal the mechanisms underlying cancer therapy efficacy, it is clear that miRNAs contribute to responses to drug therapy and are themselves modified by drug therapy. One important area for miRNA research is to understand the functions of miRNAs and the relevant signaling pathways in the initiation, progression and drug-resistance of tumors to be able to design novel, effective targeted therapeutics that directly target pathologically essential miRNAs and/or their target genes. Another area of increasing importance is the use of miRNA signatures in the diagnosis and prognosis of various types of cancers. As the study of non-coding RNAs is increasingly more popular and important, it is without doubt that the next several years of miRNA research will provide more fascinating results.

Tumor suppressor microRNA-27a in colorectal carcinogenesis and progression by targeting SGPP1 and Smad2

The aberrant expression of microRNAs (miRNAs) is associated with colorectal carcinogenesis, but the underlying mechanisms are not clear. This study showed that the miRNA-27a (miR-27a) was significantly reduced in colorectal cancer tissues and colorectal cancer cell lines, and that the reduced miR-27a was associated with distant metastasis and colorectal cancer clinical pathological stages-miR-27a was lower at stages III/IV than that at stage II. Bioinformatic and systemic biological analysis predicted several targets of miR-27a, among them SGPP1 and Smad2 were significantly affected. SGPP1 and Smad2 at mRNA and protein levels were negatively correlated with miR-27a in human colorectal cancer tissues and cancer cell lines. Increased miR-27a significantly repressed SGPP1 and Smad2 at transcriptional and translational levels. Functional studies showed that increasing miR-27a inhibited colon cancer cell proliferation, promoted apoptosis and attenuated cell migration, which were also linked to downregulation of p-STAT3 and upregulation of cleaved caspase 3. In vivo, miR-27a inhibited colon cancer cell growth in tumor-bearing mice. Taken together, this study has revealed miR-27a as a tumor suppressor and has identified SGPP1 and Smad2 as novel targets of miR-27a, linking to STAT3 for regulating cancer cell proliferation, apoptosis and migration in colorectal cancer. Therefore, miR-27a could be a useful biomarker for monitoring colorectal cancer development and progression, and also could have a therapeutic potential by targeting SGPP1, Smad2 and STAT3 for colorectal cancer therapy.

MicroRNAs: novel players in cancer diagnosis and therapies

First discovered in 1993, microRNAs (miRNAs) have been one of the hottest research areas over the past two decades. Oftentimes, miRNAs levels are found to be dysregulated in cancer patients. The potential use of miRNAs in cancer therapies is an emerging and promising field, with research finding miRNAs to play a role in cancer initiation, tumor growth, and metastasis. Therefore, miRNAs could become an integral part from cancer diagnosis to treatment in future. This review aims to examine current novel research work on the potential roles of miRNAs in cancer therapies, while also discussing several current challenges and needed future research.

Translocation t(2;11) in CLL cells results in CXCR4/MAML2 fusion oncogene

Recent investigations of chromosomal aberrations in chronic lymphocytic leukemia (CLL) led to a better understanding of the molecular causes of CLL. Here we report a rearrangement between MAML2 (mastermind-like protein 2) and CXCR4 (specific receptor for CXC chemokine stromal cell-derived factor-1) in CLL cells of a patient with a t(2;11)(q22.1;q21) chromosomal translocation. The rearrangement between MAML2 and CXCR4, created by a t(2;11)(q22.1;q21) translocation, results in a new fusion gene in which a portion of CXCR4 is linked to the MAML2 gene. This fusion gene encodes for CXCR4/MAML2 protein chimera in which the N-terminal basic domain of MAML2 is replaced by the N-terminal domain of CXCR4.

A microRNA meta-signature for pancreatic ductal adenocarcinoma

Due to its aggressive and late presentation, there is an urgent need for novel and reliable biomarkers for the diagnosis and prognostication of pancreatic ductal adenocarcinoma (PDAC). MiRNAs have been extensively profiled in PDAC tissues, biopsies, blood samples and other biofluids and their expression levels compared to normal and chronic pancreatitis (CP) specimens in order to identify the most relevant candidates. Consolidation of these activities has not been attempted until now. The evaluated meta-review by Ma et al. helps to define the use of miRNAs as biomarkers for detecting this tumor-type and predicting survival outcomes in PDAC. Based on frequency and consistency between microarray studies, they identified a miRNA meta-signature for recognising PDAC: upregulation of miR-21, 23a, 31, 100, 143, 155, and 221; with downregulation of miR-148a, 217 and 375. Furthermore, they validated high miR-21, high miR-31 and low miR-375 tumoural expression as independently prognostic for poor overall-survival (OS; n = 70).

Three-dimensional lung tumor microenvironment modulates therapeutic compound responsiveness in vitro--implication for drug development

Three-dimensional (3D) cell culture is gaining acceptance in response to the need for cellular models that better mimic physiologic tissues. Spheroids are one such 3D model where clusters of cells will undergo self-assembly to form viable, 3D tumor-like structures. However, to date little is known about how spheroid biology compares to that of the more traditional and widely utilized 2D monolayer cultures. Therefore, the goal of this study was to characterize the phenotypic and functional differences between lung tumor cells grown as 2D monolayer cultures, versus cells grown as 3D spheroids. Eight lung tumor cell lines, displaying varying levels of epidermal growth factor receptor (EGFR) and cMET protein expression, were used to develop a 3D spheroid cell culture model using low attachment U-bottom plates. The 3D spheroids were compared with cells grown in monolayer for 1) EGFR and cMET receptor expression, as determined by flow cytometry, 2) EGFR and cMET phosphorylation by MSD assay, and 3) cell proliferation in response to epidermal growth factor (EGF) and hepatocyte growth factor (HGF). In addition, drug responsiveness to EGFR and cMET inhibitors (Erlotinib, Crizotinib, Cetuximab [Erbitux] and Onartuzumab [MetMab]) was evaluated by measuring the extent of cell proliferation and migration. Data showed that EGFR and cMET expression is reduced at day four of untreated spheroid culture compared to monolayer. Basal phosphorylation of EGFR and cMET was higher in spheroids compared to monolayer cultures. Spheroids showed reduced EGFR and cMET phosphorylation when stimulated with ligand compared to 2D cultures. Spheroids showed an altered cell proliferation response to HGF, as well as to EGFR and cMET inhibitors, compared to monolayer cultures. Finally, spheroid cultures showed exceptional utility in a cell migration assay. Overall, the 3D spheroid culture changed the cellular response to drugs and growth factors and may more accurately mimic the natural tumor microenvironment.

miR-Synth: a computational resource for the design of multi-site multi-target synthetic miRNAs

RNAi is a powerful tool for the regulation of gene expression. It is widely and successfully employed in functional studies and is now emerging as a promising therapeutic approach. Several RNAi-based clinical trials suggest encouraging results in the treatment of a variety of diseases, including cancer. Here we present miR-Synth, a computational resource for the design of synthetic microRNAs able to target multiple genes in multiple sites. The proposed strategy constitutes a valid alternative to the use of siRNA, allowing the employment of a fewer number of molecules for the inhibition of multiple targets. This may represent a great advantage in designing therapies for diseases caused by crucial cellular pathways altered by multiple dysregulated genes. The system has been successfully validated on two of the most prominent genes associated to lung cancer, c-MET and Epidermal Growth Factor Receptor (EGFR). (See http://microrna.osumc.edu/mir-synth).

MicroRNA-206 induces G1 arrest in melanoma by inhibition of CDK4 and Cyclin D

Expression profiling of microRNAs in melanoma lesional skin biopsies compared with normal donor skin biopsies, as well as melanoma cell lines compared with normal melanocytes, revealed that hsa-miR-206 was down-regulated in melanoma (-75.4-fold, P = 1.7 × 10(-4)). MiR-206 has been implicated in a large number of cancers, including breast, lung, colorectal, ovarian, and prostate cancers; however, its role in tumor development remains largely unknown, its biologic function is poorly characterized, and its targets affecting cancer cells are largely unknown. MiR-206 reduced growth and migration/invasion of multiple melanoma cell lines. Bioinformatics identified cell cycle genes CDK2, CDK4, Cyclin C, and Cyclin D1 as strong candidate targets. Western blots and 3'UTR reporter gene assays revealed that miR-206 inhibited translation of CDK4, Cyclin D1, and Cyclin C. Additionally, hsa-miR-206 transfection induced G1 arrest in multiple melanoma cell lines. These observations support hsa-miR-206 as a tumor suppressor in melanoma and identify Cyclin C, Cyclin D1, and CDK4 as miR-206 targets.

microRNA-27a functions as a tumor suppressor in esophageal squamous cell carcinoma by targeting KRAS

microRNAs (miRNAs) have been suggested to play a vital role in regulating tumor progression and invasion. However, the expression of miR-27a in esophageal squamous cell carcinoma (ESCC) and its effect on the tumorigenesis of ESCC are unclear. In the present study, we found that miR-27a was downregulated in esophageal carcinoma cell lines and ESCC specimens with lymph node metastasis. Furthermore, we demonstrated that miR-27a binds to the 3'-untranslated region (UTR) of KRAS and inhibits the expression of the KRAS protein. miR-27a levels were inversely correlated with levels of KRAS mRNA and protein in ESCC specimens. Both in vitro and in vivo assays revealed that miR-27a attenuated ESCC proliferation, invasion and tumor growth in nude mice. miR-27a exerts its tumor suppressor function through inhibition of the KRAS-related ERK pathways. Our findings suggest, for the first time, that miR-27a suppresses tumorigenesis of ESCC by targeting KRAS.