A MicroRNA signature associated with prognosis and progression in chronic lymphocytic leukemia

Therapeutic microRNA strategies in human cancer

MicroRNAs (miRNAs) are approximately 22 nucleotide long, noncoding, endogenous RNA molecules which exert their functions by base pairing with messenger RNAs (mRNAs), thereby regulate protein-coding gene expression. In eukaryotic cells, miRNAs play important roles in regulating biological processes such as proliferation, differentiation, apoptosis, and stem cell self-renewal. The human genome may contain as many as 1,000 miRNAs, and more than 700 of them have been identified. miRNAs are predicted to target up to one third of mRNAs. Each miRNA can target hundreds of transcripts directly or indirectly, while more than one miRNA can converge on a single transcript target. Therefore, the potential regulatory circuitry afforded by miRNA is enormous. Recently, mounting evidence implicates miRNAs as a new class of modulator for human tumor initiation and progression. Therefore, it has been proposed that manipulating miRNA activity and miRNA biogenesis may be a novel avenue for developing efficient therapies against cancer.

Karyotype-specific microRNA signature in chronic lymphocytic leukemia

Chromosomal abnormalities, immunoglobulin heavy chain variable-region (IGHV) gene mutation status, and zeta-associated protein 70 (ZAP-70) expression levels have independent prognostic relevance in chronic lymphocytic leukemia (CLL); however, their concordance is variable. Because deregulation of microRNAs has been linked to disease initiation and progression in CLL, we studied the value of the microRNAs as a signature for CLL patients with specific chromosomal abnormalities. We identified 32 microRNAs able to discriminate the 11q deletion, 17p deletion, trisomy 12, 13q deletion, and normal karyotype cytogenetic subgroups. The expression values of 9 among the 32 microRNAs (miR-151-3p, miR-34a, miR-29c, miR-29b, miR-155, miR-148a, miR-146a, miR-146b5p, and miR-640) were correlated with gene expression data from the same samples to assess their biologic impact on CLL. In this study we also found that IGHV unmutated, high expression of ZAP-70 protein, and low expression of the miR-223, miR-29c, miR-29b, and miR-181 family were strongly associated with disease progression in CLL cases harboring 17p deletion, whereas in those harboring trisomy 12 only high expression of the miR-181a, among the analyzed parameters, suggested more aggressive disease. Thus, the use of the microRNA-based classifications may yield clinically useful biomarkers of tumor behavior in CLL.

MicroRNA expression profiling in acute myeloid and chronic lymphocytic leukaemias

Altered expression of microRNAs, a new class of noncoding RNAs that regulate messenger RNA and protein expression of target genes, has been recently demonstrated to have an essential role in the process of leukaemogenesis. Distinctive patterns of activation and/or silencing of multiple microRNAs (microRNA signatures) associated with certain cytogenetic and molecular subsets of leukaemia have been identified using genome-wide high-throughput profiling assays. This has led not only to the discovery of new molecular pathways implicated in leukaemogenesis, but also supplied prognostic information complementing that gained from cytogenetics, gene mutations and altered gene expression in acute and chronic leukaemias. We review herein results of current studies analysing changes of microRNA expression in acute myeloid leukaemia and chronic lymphocytic leukaemia, and discuss their potential biologic, diagnostic and prognostic relevance.

Investigation of the miR16-1 (C > T) + 7 Substitution in Seven Different Types of Cancer from Three Ethnic Groups

Background. MicroRNAs are a type of small noncoding RNA molecules that have been shown to control gene expression in eukaryotes. Aberrant expression and alteration of miRNAs may be responsible for human diseases including cancer. An miR16-1 (C > T) + 7 gene mutation has been previously found in familial chronic lymphocytic leukemia patients, one of which reported a family history of breast cancer. miR16-1 regulates the expression of bcl-2, which is important in retinoblastoma, and is located in a genomic region that is frequently lost in nasopharyngeal and hepatocellular carcinomas (HCCs). Therefore, miR16-1 may be potentially important in the etiology of several solid tumors. To understand the power of the miR16-1 (C > T) + 7 mutation as a prognostic and diagnostic risk factor, we investigated the mutation in patients with seven different types of cancer including 188 with breast, 102 with ovarian, and 22 nasopharyngeal carcinomas, 96 HCC, 872 chronic myeloid leukemia (CML), 39 chronic lymphocytic leukemia (CLL), and 46 retinoblastoma cases from three different ethnic groups and of hereditary and sporadic etiology. Methods. 5′Nuclease TaqMan SNP genotyping assay was used to detect the miR16-1 gene C > T substitution. Results. The miR16-1 (C > T) + 7 substitution was not detected in any of the groups studied. Conclusions. Considering the large scale of our study, the representation of different ethnicities and levels of hereditary risk, we conclude that the miR-16-1 (C > T) + 7 mutation is not a good diagnostic or prognostic indicator of risk for the cancers tested.

Antagonism of microRNA-126 suppresses the effector function of TH2 cells and the development of allergic airways disease

Allergic asthma is an inflammatory disease of the lung characterized by abnormal T helper-2 (T(H)2) lymphocyte responses to inhaled antigens. The molecular mechanisms leading to the generation of T(H)2 responses remain unclear, although toll-like receptors (TLRs) present on innate immune cells play a pivotal role in sensing molecular patterns and in programming adaptive T cell responses. Here we show that in vivo activation of TLR4 by house dust mite antigens leads to the induction of allergic disease, a process that is associated with expression of a unique subset of small, noncoding microRNAs. Selective blockade of microRNA (miR)-126 suppressed the asthmatic phenotype, resulting in diminished T(H)2 responses, inflammation, airways hyperresponsiveness, eosinophil recruitment, and mucus hypersecretion. miR-126 blockade resulted in augmented expression of POU domain class 2 associating factor 1, which activates the transcription factor PU.1 that alters T(H)2 cell function via negative regulation of GATA3 expression. In summary, this study presents a functional connection between miRNA expression and asthma pathogenesis, and our data suggest that targeting miRNA in the airways may lead to anti-inflammatory treatments for allergic asthma.

MicroRNA expression, survival, and response to interferon in liver cancer

BACKGROUND

Hepatocellular carcinoma is a common and aggressive cancer that occurs mainly in men. We examined microRNA expression patterns, survival, and response to interferon alfa in both men and women with the disease.

METHODS

We analyzed three independent cohorts that included a total of 455 patients with hepatocellular carcinoma who had undergone radical tumor resection between 1999 and 2003. MicroRNA-expression profiling was performed in a cohort of 241 patients with hepatocellular carcinoma to identify tumor-related microRNAs and determine their association with survival in men and women. In addition, to validate our findings, we used quantitative reverse-transcriptase-polymerase-chain-reaction assays to measure microRNAs and assess their association with survival and response to therapy with interferon alfa in 214 patients from two independent, prospective, randomized, controlled trials of adjuvant interferon therapy.

RESULTS

In patients with hepatocellular carcinoma, the expression of miR-26a and miR-26b in nontumor liver tissue was higher in women than in men. Tumors had reduced levels of miR-26 expression, as compared with paired noncancerous tissues, which indicated that the level of miR-26 expression was also associated with hepatocellular carcinoma. Moreover, tumors with reduced miR-26 expression had a distinct transcriptomic pattern, and analyses of gene networks revealed that activation of signaling pathways between nuclear factor kappaB and interleukin-6 might play a role in tumor development. Patients whose tumors had low miR-26 expression had shorter overall survival but a better response to interferon therapy than did patients whose tumors had high expression of the microRNA.

CONCLUSIONS

The expression patterns of microRNAs in liver tissue differ between men and women with hepatocellular carcinoma. The miR-26 expression status of such patients is associated with survival and response to adjuvant therapy with interferon alfa.

Predicting respiratory tumor motion with multi-dimensional adaptive filters and support vector regression

Intra-fraction tumor tracking methods can improve radiation delivery during radiotherapy sessions. Image acquisition for tumor tracking and subsequent adjustment of the treatment beam with gating or beam tracking introduces time latency and necessitates predicting the future position of the tumor. This study evaluates the use of multi-dimensional linear adaptive filters and support vector regression to predict the motion of lung tumors tracked at 30 Hz. We expand on the prior work of other groups who have looked at adaptive filters by using a general framework of a multiple-input single-output (MISO) adaptive system that uses multiple correlated signals to predict the motion of a tumor. We compare the performance of these two novel methods to conventional methods like linear regression and single-input, single-output adaptive filters. At 400 ms latency the average root-mean-square-errors (RMSEs) for the 14 treatment sessions studied using no prediction, linear regression, single-output adaptive filter, MISO and support vector regression are 2.58, 1.60, 1.58, 1.71 and 1.26 mm, respectively. At 1 s, the RMSEs are 4.40, 2.61, 3.34, 2.66 and 1.93 mm, respectively. We find that support vector regression most accurately predicts the future tumor position of the methods studied and can provide a RMSE of less than 2 mm at 1 s latency. Also, a multi-dimensional adaptive filter framework provides improved performance over single-dimension adaptive filters. Work is underway to combine these two frameworks to improve performance.

MicroRNA profiling of BRCA1/2 mutation-carrying and non-mutation-carrying high-grade serous carcinomas of ovary

BACKGROUND

MicroRNAs (miRNA) are 20 approximately 25 nucleotide non-coding RNAs that inhibit the translation of targeted mRNA, and they have been implicated in the development of human malignancies. High grade serous ovarian carcinomas, the most common and lethal subtype of ovarian cancer, can occur sporadically or in the setting of BRCA1/2 syndromes. Little is known regarding the miRNA expression profiles of high grade serous carcinoma in relation to BRCA1/2 status, and compared to normal tubal epithelium, the putative tissue of origin for high grade serous carcinomas.

METHODOLOGY/PRINCIPAL FINDINGS

Global miRNA expression profiling was performed on a series of 33 high grade serous carcinomas, characterized with respect to BRCA1/2 status (mutation, epigenetic silencing with loss of expression or normal), and with clinical follow-up, together with 2 low grade serous carcinomas, 2 serous borderline tumors, and 3 normal fallopian tube samples, using miRNA microarrays (328 human miRNA). Unsupervised hierarchical clustering based on miRNA expression profiles showed no clear separation between the groups of carcinomas with different BRCA1/2 status. There were relatively few miRNAs that were differentially expressed between the genotypic subgroups. Comparison of 33 high grade serous carcinomas to 3 normal fallopian tube samples identified several dysregulated miRNAs (false discovery rate <5%), including miR-422b and miR-34c. Quantitative RT-PCR analysis performed on selected miRNAs confirmed the pattern of differential expression shown by microarray analysis. Prognostically, lower level miR-422b and miR-34c in high grade serous carcinomas were both associated with decreased disease-specific survival by Kaplan-Meier analysis (p<0.05).

CONCLUSIONS/SIGNIFICANCE

High grade serous ovarian carcinomas with and without BRCA1/2 abnormalities demonstrate very similar miRNA expression profiles. High grade serous carcinomas as a group exhibit significant miRNA dysregulation in comparison to tubal epithelium and the levels of miR-34c and miR-422b appear to be prognostically important.

Causes and consequences of microRNA dysregulation in cancer

Over the past several years it has become clear that alterations in the expression of microRNA (miRNA) genes contribute to the pathogenesis of most--if not all--human malignancies. These alterations can be caused by various mechanisms, including deletions, amplifications or mutations involving miRNA loci, epigenetic silencing or the dysregulation of transcription factors that target specific miRNAs. Because malignant cells show dependence on the dysregulated expression of miRNA genes, which in turn control or are controlled by the dysregulation of multiple protein-coding oncogenes or tumour suppressor genes, these small RNAs provide important opportunities for the development of future miRNA-based therapies.

MicroRNA expression profiling of human metastatic cancers identifies cancer gene targets

Small non-coding microRNAs (miRNAs) contribute to cancer development and progression, and are differentially expressed in normal tissues and cancers. However, the specific role of miRNAs in the metastatic process is still unknown. To seek a specific miRNA expression signature characterizing the metastatic phenotype of solid tumours, we performed a miRNA microarray analysis on 43 paired primary tumours (ten colon, ten bladder, 13 breast, and ten lung cancers) and one of their related metastatic lymph nodes. We identified a metastatic cancer miRNA signature comprising 15 overexpressed and 17 underexpressed miRNAs. Our results were confirmed by qRT-PCR analysis. Among the miRNAs identified, some have a well-characterized association with cancer progression, eg miR-10b, miR-21, miR-30a, miR-30e, miR-125b, miR-141, miR-200b, miR-200c, and miR-205. To further support our data, we performed an immunohistochemical analysis for three well-defined miRNA gene targets (PDCD4, DHFR, and HOXD10 genes) on a small series of paired colon, breast, and bladder cancers, and one of their metastatic lymph nodes. We found that the immunohistochemical expression of these targets significantly follows the corresponding miRNA deregulation. Our results suggest that specific miRNAs may be directly involved in cancer metastasis and that they may represent a novel diagnostic tool in the characterization of metastatic cancer gene targets.

Antisense inhibition of microRNA-21 or -221 arrests cell cycle, induces apoptosis, and sensitizes the effects of gemcitabine in pancreatic adenocarcinoma

OBJECTIVES

The contribution of overexpressed microRNA-21 and -221 (miR-21 and miR-221) to the malignant phenotype was determined by inhibiting these miRNAs using antisense oligonucleotides.

METHODS

The effects of antisense to miR-21 and miR-221 on cell proliferation, cell cycle arrest, induction of apoptosis, combinatorial effects with gemcitabine, and effects on target protein levels were studied.

RESULTS

Low nanomolar concentrations of both antisense oligonucleotides reduced proliferation of pancreatic cancer cell lines. Reduced proliferation was less pronounced in the normal ductal epithelial cell line human pancreatic Nestin-expressing cell or in pancreatic cancer cell lines exposed to an irrelevant control oligonucleotide. Inhibition of miR-21 and miR-221 increased the amount of apoptosis in HS766T cells by 3- to 6-fold compared with the control oligonucleotide. HS766T cells exposed to miR-21 antisense resulted in cell cycle arrest (G1 phase). Protein levels of tumor suppressor targets of the miRNAs were increased by antisense to miR-21 (PTEN and RECK) and miR-221 (p27). Antisense to miR-21 and miR-221 sensitized the effects of gemcitabine, and the antisense-gemcitabine combinations were synergistic at high fraction affected.

CONCLUSIONS

We demonstrate that antisense to miR-21 and miR-221 results in significant cell killing under various conditions and that antisense oligonucleotides targeted to miRNA represents a potential new therapy for pancreatic cancer.

miR-24 Inhibits cell proliferation by targeting E2F2, MYC, and other cell-cycle genes via binding to "seedless" 3'UTR microRNA recognition elements

miR-24, upregulated during terminal differentiation of multiple lineages, inhibits cell-cycle progression. Antagonizing miR-24 restores postmitotic cell proliferation and enhances fibroblast proliferation, whereas overexpressing miR-24 increases the G1 compartment. The 248 mRNAs downregulated upon miR-24 overexpression are highly enriched for DNA repair and cell-cycle regulatory genes that form a direct interaction network with prominent nodes at genes that enhance (MYC, E2F2, CCNB1, and CDC2) or inhibit (p27Kip1 and VHL) cell-cycle progression. miR-24 directly regulates MYC and E2F2 and some genes that they transactivate. Enhanced proliferation from antagonizing miR-24 is abrogated by knocking down E2F2, but not MYC, and cell proliferation, inhibited by miR-24 overexpression, is rescued by miR-24-insensitive E2F2. Therefore, E2F2 is a critical miR-24 target. The E2F2 3'UTR lacks a predicted miR-24 recognition element. In fact, miR-24 regulates expression of E2F2, MYC, AURKB, CCNA2, CDC2, CDK4, and FEN1 by recognizing seedless but highly complementary sequences.

MicroRNA involvement in the pathogenesis and management of breast cancer

MicroRNAs (miRNAs) are a highly abundant class of endogenous small non-coding RNAs (18-25 nucleotides in length) that regulate gene expression by targeting protein-coding mRNAs post-transcriptionally. miRNAs have been implicated in cancer development and progression. As miRNAs and their regulatory functions are further revealed, the more the importance of miRNA-directed gene regulation is emphasised. In the human genome, 695 mature miRNAs have been identified, although computational calculation predicts that this may increase to >1000. Deregulation of miRNA expression profiles is thought to be implicated in the pathogenesis of many human cancers including breast tumours. Breast cancer subtypes are observed to have deranged miRNA expression signatures, which makes miRNAs important targets for developing a novel molecular classification of breast cancer and opening avenues for more individualised treatment strategies for patients with breast cancer.

Molecular diagnosis of hematopoietic and lymphoid neoplasms

This chapter summarizes the significance and molecular diagnostic detection of genetic abnormalities commonly associated with hematolymphoid neoplasms. Methodologic aspects of laboratory diagnosis are presented, as well as discussion of multiparameter genotyping of tumors for prognosis and the role of minimal residual disease monitoring in specific neoplasms.

Identification of a microRNA signature associated with progression of leukoplakia to oral carcinoma

MicroRNAs (miRs) are non-coding RNA molecules involved in cancer initiation and progression. Deregulated miR expression has been implicated in cancer; however, there are no studies implicating an miR signature associated with progression in oral squamous cell carcinoma (OSCC). Although OSCC may develop from oral leukoplakia, clinical and histological assessments have limited prognostic value in predicting which leukoplakic lesions will progress. Our aim was to quantify miR expression changes in leukoplakia and same-site OSCC and to identify an miR signature associated with progression. We examined miR expression changes in 43 sequential progressive samples from 12 patients and four non-progressive leukoplakias from four different patients, using TaqMan Low Density Arrays. The findings were validated using quantitative RT-PCR in an independent cohort of 52 progressive dysplasias and OSCCs, and five non-progressive dysplasias. Global miR expression profiles distinguished progressive leukoplakia/OSCC from non-progressive leukoplakias/normal tissues. One hundred and nine miRs were highly expressed exclusively in progressive leukoplakia and invasive OSCC. miR-21, miR-181b and miR-345 expressions were consistently increased and associated with increases in lesion severity during progression. Over-expression of miR-21, miR-181b and miR-345 may play an important role in malignant transformation. Our study provides the first evidence of an miR signature potentially useful for identifying leukoplakias at risk of malignant transformation.

MicroRNA dynamics in the stages of tumorigenesis correlate with hallmark capabilities of cancer

While altered expression of microRNAs (miRs) in tumors has been well documented, it remains unclear how the miR transcriptome intersects neoplastic progression. By profiling the miR transcriptome we identified miR expression signatures associated with steps in tumorigenesis and the acquisition of hallmark capabilities in a prototypical mouse model of cancer. Metastases and a rare subset of primary tumors shared a distinct miR signature, implicating a discrete lineage for metastatic tumors. The miR-200 family is strongly down-regulated in metastases and met-like primary tumors, thereby relieving repression of the mesenchymal transcription factor Zeb1, which in turn suppresses E-cadherin. Treatment with a clinically approved angiogenesis inhibitor normalized angiogenic signature miRs in primary tumors, while altering expression of metastatic signature miRs similarly to liver metastases, suggesting their involvement in adaptive resistance to anti-angiogenic therapy via enhanced metastasis. Many of the miR changes associated with specific stages and hallmark capabilities in the mouse model are similarly altered in human tumors, including cognate pancreatic neuroendocrine tumors, implying a generality.

MicroRNAs in Barrett's esophagus and esophageal adenocarcinoma

The molecular genetics of Barrett's esophagus (BE) and its evolution to esophageal adenocarcinoma (EAC) have been widely studied; however, the molecular mechanism of BE-EAC carcinogenesis has not been completely understood. MicroRNA (miRNA) is now essential to understand the molecular mechanism of cancer progression. Recent findings include the following: firstly, miRNA expression profiles can distinguish between BE and EAC; secondly, miR-196a is upregulated in EAC tissues targeting annexin A1, thereby exerting antiapoptotic effects and contributing to EAC cell survival; miR-196a may also constitute a good biomarker of progression during BE-EAC carcinogenesis; and thirdly, The miR-106b-25 polycistron is activated by genomic amplification and is involved in esophageal neoplastic progression and proliferation via the suppression of two target genes, p21 and Bim.

Multi-class cancer classification through gene expression profiles: microRNA versus mRNA

Both microRNA (miRNA) and mRNA expression profiles are important methods for cancer type classification. A comparative study of their classification performance will be helpful in choosing the means of classification. Here we evaluated the classification performance of miRNA and mRNA profiles using a new data mining approach based on a novel SVM (Support Vector Machines) based recursive feature elimination (nRFE) algorithm. Computational experiments showed that information encoded in miRNAs is not sufficient to classify cancers; gut-derived samples cluster more accurately when using mRNA expression profiles compared with using miRNA profiles; and poorly differentiated tumors (PDT) could be classified by mRNA expression profiles at the accuracy of 100% versus 93.8% when using miRNA profiles. Furthermore, we showed that mRNA expression profiles have higher capacity in normal tissue classifications than miRNA. We concluded that classification performance using mRNA profiles is superior to that of miRNA profiles in multiple-class cancer classifications.

The emerging role of microRNAs in immune cell development and differentiation

MicroRNAs (miRNAs) are small RNA strands (20-25 nucleotides) that regulate gene expression by translational repression as well as by messenger RNA degradation. This review will examine the application and function of miRNAs in immune cell development and differentiation.

Two new miR-16 targets: caprin-1 and HMGA1, proteins implicated in cell proliferation

BACKGROUND INFORMATION

miRNAs (microRNAs) are a class of non-coding RNAs that inhibit gene expression by binding to recognition elements, mainly in the 3' UTR (untranslated region) of mRNA. A single miRNA can target several hundred mRNAs, leading to a complex metabolic network. miR-16 (miRNA-16), located on chromosome 13q14, is involved in cell proliferation and apoptosis regulation; it may interfere with either oncogenic or tumour suppressor pathways, and is implicated in leukaemogenesis. These data prompted us to search for and validate novel targets of miR-16.

RESULTS

In the present study, by using a combined bioinformatics and molecular approach, we identified two novel putative targets of miR-16, caprin-1 (cytoplasmic activation/proliferation-associated protein-1) and HMGA1 (high-mobility group A1), and we also studied cyclin E which had been previously recognized as an miR-16 target by bioinformatics database. Using luciferase activity assays, we demonstrated that miR-16 interacts with the 3' UTR of the three target mRNAs. We showed that miR-16, in MCF-7 and HeLa cell lines, down-regulates the expression of caprin-1, HMGA1a, HMGA1b and cyclin E at the protein level, and of cyclin E, HMGA1a and HMGA1b at the mRNA levels.

CONCLUSIONS

Taken together, our data demonstrated that miR-16 can negatively regulate two new targets, HMGA1 and caprin-1, which are involved in cell proliferation. In addition, we also showed that the inhibition of cyclin E expression was due, at least in part, to a decrease in its mRNA stability.

Association of inflammation-related and microRNA gene expression with cancer-specific mortality of colon adenocarcinoma

PURPOSE

Inflammatory genes and microRNAs have roles in colon carcinogenesis; therefore, they may provide useful biomarkers for colon cancer. This study examines the potential clinical utility of an inflammatory gene expression signature as a prognostic biomarker for colon cancer in addition to previously examined miR-21 expression.

EXPERIMENTAL DESIGN

Quantitative reverse transcriptase-PCR. was used to measure the expression of 23 inflammatory genes in colon adenocarcinomas and adjacent noncancerous tissues from 196 patients. These data were used to develop models for cancer-specific mortality on a training cohort (n = 57), and this model was tested in both a test (n = 56) and a validation (n = 83) cohort. Expression data for miR-21 were available for these patients and were compared and combined with inflammatory gene expression.

RESULTS

PRG1, IL-10, CD68, IL-23a, and IL-12a expression in noncancerous tissue, and PRG1, ANXA1, IL-23a, IL-17a, FOXP3, and HLA-DRA expression in tumor tissues were associated with poor prognosis based on Cox regression (/Z-score/ >1.5) and were used to generate the inflammatory risk score (IRS). IRS was associated with cancer-specific mortality in the training, test (P = 0.01), and validation (P = 0.02) cohorts. This association was strong for stage II cases (P = 0.002). Expression of miR-21 was associated with IL-6, IL-8, IL-10, IL-12a, and NOS2a, providing evidence that the function of this microRNA and these inflammatory genes are linked. Both IRS and miR-21 expression were independently associated with cancer-specific mortality, including stage II patients alone.

CONCLUSION

IRS and miR-21 expression are independent predictors of colon cancer prognosis and may provide a clinically useful tool to identify high-risk patients.

Systemic delivery of synthetic microRNA-16 inhibits the growth of metastatic prostate tumors via downregulation of multiple cell-cycle genes

Recent reports have linked the expression of specific microRNAs (miRNAs) with tumorigenesis and metastasis. Here, we show that microRNA (miR)-16, which is expressed at lower levels in prostate cancer cells, affects the proliferation of human prostate cancer cell lines both in vitro and in vivo. Transient transfection with synthetic miR-16 significantly reduced cell proliferation of 22Rv1, Du145, PPC-1, and PC-3M-luc cells. A prostate cancer xenograft model revealed that atelocollagen could efficiently deliver synthetic miR-16 to tumor cells on bone tissues in mice when injected into tail veins. In the therapeutic bone metastasis model, injection of miR-16 with atelocollagen via tail vein significantly inhibited the growth of prostate tumors in bone. Cell model studies indicate that miR-16 likely suppresses prostate tumor growth by regulating the expression of genes such as CDK1 and CDK2 associated with cell-cycle control and cellular proliferation. There is a trend toward lower miR-16 expression in human prostate tumors versus normal prostate tissues. Thus, this study indicates the therapeutic potential of miRNA in an animal model of cancer metastasis with systemic miRNA injection and suggest that systemic delivery of miR-16 could be used to treat patients with advanced prostate cancer.

miRNA analysis of prostate cancer by quantitative real time PCR: comparison between formalin-fixed paraffin embedded and fresh-frozen tissue

OBJECTIVE

Micro RNA (miRNA) is a class of small noncoding RNA that plays a major role in the regulation of gene expression, which has been related to cancer behavior. The possibility of analyzing miRNA from the archives of pathology laboratories is exciting, as it allows for large retrospective studies. Formalin is the most common fixative used in the surgical pathology routine, and its promotion of nucleic acid degradation is well known. Our aim is to compare miRNA profiles from formalin-fixed paraffin embedded (FFPE) tissues with fresh-frozen prostate cancer tissues.

METHODS

The expression of 14 miRNAs was determined by quantitative real time polymerase chain reaction (qRT-PCR) in 5 paired fresh-frozen and FFPE tissues, which were representative of prostate carcinoma.

RESULTS

There was a very good correlation of the miRNA expression of miR-let7c and miR-32 between the fresh-frozen and FFPE tissues, with Pearson's correlation coefficients of 0.927 (P = 0.023) and 0.960 (P = 0.010), respectively. For the remaining miRNAs, the correlation was good with Spearman correlation coefficient of 0.638 (P < 0.001).

CONCLUSION

Analysis of miRNAs from routinely processed and stored FFPE prostate tissue is feasible for some miRNAs using qRT-PCR. Further studies should be conducted to confirm the reliability of using stock tissues for miRNA expression determination.

Linking metastasis suppression with metastamiR regulation

Cancer metastasis requires the coordinate expression of multiple genes during every step of the metastatic cascade. Molecules that regulate these genetic programs have the potential to impact metastasis at multiple levels. Breast cancer metastasis suppressor 1 (BRMS1) suppresses metastasis by inhibiting multiple steps in the cascade through regulation of many protein-encoding, metastasis-associated genes as well as metastasis-regulatory microRNA, termed metastamiR. In this Feature , we will highlight connections between BRMS1 biology and regulation of metastamiR.

The TCL1 mouse as a model for chronic lymphocytic leukemia

The TCL1 mouse has been proposed as a mouse model for chronic lymphocytic leukemia. This review details how it resembles the aggressive form of the disease rather than the more common indolent form. Although fulfilled predictions in the human disease based on investigations in the mouse model are at present lacking, there are remarkable similarities between human and mouse leukemias that have led to interesting observations on the pathophysiology of chronic lymphocytic leukemia and have identified putative therapeutic targets.

MicroRNAs with a nucleolar location

There is increasing evidence that noncoding RNAs play a functional role in the nucleus. We previously reported that the microRNA (miRNA), miR-206, is concentrated in the nucleolus of rat myoblasts, as well as in the cytoplasm as expected. Here we have extended this finding. We show by cell/nuclear fractionation followed by microarray analysis that a number of miRNAs can be detected within the nucleolus of rat myoblasts, some of which are significantly concentrated there. Pronounced nucleolar localization is a specific phenomenon since other miRNAs are present at only very low levels in the nucleolus and occur at much higher levels in the nucleoplasm and/or the cytoplasm. We have further characterized a subset of these miRNAs using RT-qPCR and in situ hybridization, and the results suggest that some miRNAs are present in the nucleolus in precursor form while others are present as mature species. Furthermore, we have found that these miRNAs are clustered in specific sites within the nucleolus that correspond to the classical granular component. One of these miRNAs is completely homologous to a portion of a snoRNA, suggesting that it may be processed from it. In contrast, the other nucleolar-concentrated miRNAs do not show homology with any annotated rat snoRNAs and thus appear to be present in the nucleolus for other reasons, such as modification/processing, or to play roles in the late stages of ribosome biosynthesis or in nonribosomal functions that have recently been ascribed to the granular component of the nucleolus.

Correcting miR-15a/16 genetic defect in New Zealand Black mouse model of CLL enhances drug sensitivity

Alterations in the human 13q14 genomic region containing microRNAs mir-15a and mir-16-1 are present in most human chronic lymphocytic leukemia (CLL). We have previously found the development of CLL in the New Zealand Black murine model to be associated with a point mutation in the primary mir-15a/16-1 region, which correlated with a decrease in mature miR-16 and miR-15a levels. In this study, addition of exogenous miR-15a and miR-16 led to an accumulation of cells in G(1) in non-New Zealand Black B cell and New Zealand Black-derived malignant B-1 cell lines. However, the New Zealand Black line had significantly greater G(1) accumulation, suggesting a restoration of cell cycle control upon exogenous miR-15a/16 addition. Our experiments showed a reduction in protein levels of cyclin D1, a miR-15a/16 target and cell cycle regulator of G(1)/S transition, in the New Zealand Black cell line following miR-15a/16 addition. These microRNAs were shown to directly target the cyclin D1 3' untranslated region using a green fluorescent protein lentiviral expression system. miR-16 was also shown to augment apoptosis induction by nutlin, a mouse double minute 2 (MDM2) antagonist, and genistein, a tyrosine kinase inhibitor, when added to a B-1 cell line derived from multiple in vivo passages of malignant B-1 cells from New Zealand Black mice with CLL. miR-16 synergized with nutlin and genistein to induce apoptosis. Our data support a role for the mir-15a/16-1 cluster in cell cycle regulation and suggest that these mature microRNAs in both the New Zealand Black model and human CLL may be targets for therapeutic efficacy in this disease.

Emerging role of microRNAs in diagnosis and treatment of various diseases including ovarian cancer

MicroRNAs (miRNAs) represent a class of small non-coding RNAs that control gene expression by targeting messenger RNA (mRNA). Recently, it has been demonstrated that miRNA expression is altered in many human diseases including cancers, suggesting that miRNA may play a potential role in the pathogenesis of different diseases. It has also been reported that there is a unique expression pattern of miRNAs in the disease state differing from the normal state. In this review, we focus on the miRNA signatures in different human diseases including cancers. Such signatures may be used as diagnostic and prognostic markers.

microRNA profiling identifies cancer-specific and prognostic signatures in pediatric malignancies

PURPOSE

microRNAs have been shown to be involved in different human cancers. We therefore have performed expression profiles on a panel of pediatric tumors to identify cancer-specific microRNAs. We also investigated if microRNAs are coregulated with their host gene.

EXPERIMENTAL DESIGN

We performed parallel microRNAs and mRNA expression profiling on 57 tumor xenografts and cell lines representing 10 different pediatric solid tumors using microarrays. For those microRNAs that map to their host mRNA, we calculated correlations between them.

RESULTS

We found that the majority of cancer types clustered together based on their global microRNA expression profiles by unsupervised hierarchical clustering. Fourteen microRNAs were significantly differentially expressed between rhabdomyosarcoma and neuroblastoma, and 8 of them were validated in independent patient tumor samples. Exploration of the expression of microRNAs in relationship with their host genes showed that the expression for 43 of 68 (63%) microRNAs located inside known coding genes was significantly correlated with that of their host genes. Among these 43 microRNAs, 5 of 7 microRNAs in the OncomiR-1 cluster correlated significantly with their host gene MIRHG1 (P < 0.01). In addition, high expression of MIRHG1 was significantly associated with high stage and MYCN amplification in neuroblastoma tumors, and the expression level of MIRHG1 could predict the outcome of neuroblastoma patients independently from the current neuroblastoma risk-stratification in two independent patient cohorts.

CONCLUSION

Pediatric cancers express cancer-specific microRNAs. The high expression of the OncomiR-1 host gene MIRHG1 correlates with poor outcome for patients with neuroblastoma, indicating important oncogenic functions of this microRNA cluster in neuroblastoma biology.

Epigenetics, miRNAs, and human cancer: a new chapter in human gene regulation

Cancer is a genetic and epigenetic disease. MicroRNAs (miRNAs), a class of small noncoding RNAs, have been shown to be deregulated in many diseases including cancer. An intertwined connection between epigenetics and miRNAs has been supported by the recent identification of a specific subgroup of miRNAs called "epi-miRNAs" that can directly and indirectly modulate the activity of the epigenetic machinery. The complexity of this connection is enhanced by the epigenetic regulation of miRNA expression that generates a fine regulatory feedback loop. This review focuses on how epigenetics affects the miRNome and how the recently identified epi-miRNAs regulate the epigenome in human cancers, ultimately contributing to human carcinogenesis.

Repression of the miR-17-92 cluster by p53 has an important function in hypoxia-induced apoptosis

We here report that miR-17-92 cluster is a novel target for p53-mediated transcriptional repression under hypoxia. We found the expression levels of miR-17-92 cluster were reduced in hypoxia-treated cells containing wild-type p53, but were unchanged in hypoxia-treated p53-deficient cells. The repression of miR-17-92 cluster under hypoxia is independent of c-Myc. Luciferase reporter assays mapped the region responding to p53-mediated repression to a p53-binding site in the proximal region of the miR-17-92 promoter. Chromatin immunoprecipitation (ChIP), Re-ChIP and gel retardation assays revealed that the binding sites for p53- and the TATA-binding protein (TBP) overlap within the miR-17-92 promoter; these proteins were found to compete for binding. Finally, we show that pri-miR-17-92 expression correlated well with p53 status in colorectal carcinomas. Over-express miR-17-92 cluster markedly inhibits hypoxia-induced apoptosis, whereas blocked miR-17-5p and miR-20a sensitize the cells to hypoxia-induced apoptosis. These data indicated that p53-mediated repression of miR-17-92 expression likely has an important function in hypoxia-induced apoptosis, and thus further our understanding of the tumour suppressive function of p53.

Plasma miR-208 as a biomarker of myocardial injury

BACKGROUND

MicroRNAs (miRNAs) are endogenous small RNAs of 21-25 nucleotides that can pair with sites in 3' untranslated regions in mRNAs of protein-coding genes to downregulate their expression. Recently, circulating miRNAs have been reported as promising biomarkers for various pathologic conditions. We assessed the hypothesis that miRNAs may leak into the circulating blood from injured cells and thereby serve as biomarkers for identifying the injured cell type.

METHODS

We used isoproterenol-induced myocardial injury in rats as a model and miRNA array analyses to identify candidate miRNAs specifically produced in the ventricles of the heart. Individual miRNA concentrations were measured by real-time reverse-transcription PCR. Plasma cardiac troponin I (cTnI) concentrations were measured with an ELISA.

RESULTS

Array analyses revealed miR-208 to be produced exclusively in the heart, and we selected this miRNA as a possible biomarker of myocardial injury. Plasma concentrations of miR-208 increased significantly (P < 0.0001) after isoproterenol-induced myocardial injury and showed a similar time course to the concentration of cTnI, a classic biomarker of myocardial injury.

CONCLUSIONS

The plasma concentration of miR-208 may be a useful indicator of myocardial injury. Our results suggest that profiling of circulating miRNAs may help identify promising biomarkers of various pathologic conditions.

Prognostic value of Dicer expression in human breast cancers and association with the mesenchymal phenotype

BACKGROUND

Dicer, a ribonuclease, is the key enzyme required for the biogenesis of microRNAs and small interfering RNAs and is essential for both mammalian development and cell differentiation. Recent evidence indicates that Dicer may also be involved in tumourigenesis. However, no studies have examined the clinical significance of Dicer at both the RNA and the protein levels in breast cancer.

METHODS

In this study, the biological and prognostic value of Dicer expression was assessed in breast cancer cell lines, breast cancer progression cellular models, and in two well-characterised sets of breast carcinoma samples obtained from patients with long-term follow-up using tissue microarrays and quantitative reverse transcription-PCR.

RESULTS

We have found that Dicer protein expression is significantly associated with hormone receptor status and cancer subtype in breast tumours (ER P=0.008; PR P=0.019; cancer subtype P=0.023, luminal A P=0.0174). Dicer mRNA expression appeared to have an independent prognostic impact in metastatic disease (hazard ratio=3.36, P=0.0032). In the breast cancer cell lines, lower Dicer expression was found in cells harbouring a mesenchymal phenotype and in metastatic bone derivatives of a breast cancer cell line. These findings suggest that the downregulation of Dicer expression may be related to the metastatic spread of tumours.

CONCLUSION

Assessment of Dicer expression may facilitate prediction of distant metastases for patients suffering from breast cancer.

MicroRNA expression, chromosomal alterations, and immunoglobulin variable heavy chain hypermutations in Mantle cell lymphomas

The contribution of microRNAs (miR) to the pathogenesis of mantle cell lymphoma (MCL) is not well known. We investigated the expression of 86 mature miRs mapped to frequently altered genomic regions in MCL in CD5(+)/CD5(-) normal B cells, reactive lymph nodes, and purified tumor cells of 17 leukemic MCL, 12 nodal MCL, and 8 MCL cell lines. Genomic alterations of the tumors were studied by single nucleotide polymorphism arrays and comparative genomic hybridization. Leukemic and nodal tumors showed a high number of differentially expressed miRs compared with purified normal B cells, but only some of them were commonly deregulated in both tumor types. An unsupervised analysis of miR expression profile in purified leukemic MCL cells revealed two clusters of tumors characterized by different mutational status of the immunoglobulin genes, proliferation signature, and number of genomic alterations. The expression of most miRs was not related to copy number changes in their respective chromosomal loci. Only the levels of miRs included in the miR-17-92 cluster were significantly related to genetic alterations at 13q31. Moreover, overexpression of miR-17-5p/miR-20a from this cluster was associated with high MYC mRNA levels in tumors with a more aggressive behavior. In conclusion, the miR expression pattern of MCL is deregulated in comparison with normal lymphoid cells and distinguishes two subgroups of tumors with different biological features.

Chronic lymphocytic leukemia and 13q14: miRs and more

Loss of a critical region in 13q14.3 [del(13q)] is the most common genomic aberration in chronic lymphocytic leukemia (CLL), occurring in more than 50% of patients (Stilgenbauer et al., Oncogene 1998;16:1891 - 1897, Dohner et al., N Engl J Med 2000;343:1910 - 1916). Despite extensive investigations, no point mutations have been found in the remaining allele that would inactivate one of the candidate tumor suppressor genes and explain the pathomechanism postulated for this region. However, the genes in the region are significantly down-regulated in CLL cells, more than would be expected by gene dosage, and recently a complex epigenetic regulatory mechanism was identified for 13q14.3 in non-malignant cells that involves asynchronous replication timing and monoallelic expression of candidate tumor suppressor genes. Here, we propose a model of a multigenic pathomechanism in 13q14.3, where several tumor suppressor genes, including the miRNA genes miR-16-1 and miR-15a, are co-regulated by the two long non-coding RNA genes DLEU1 and DLEU2 that span the critical region. Furthermore, we propose these co-regulated genes to be involved in the same molecular pathways, thereby also forming a functional gene cluster. Elucidating the molecular and cellular function of the 13q14.3 candidate genes will shed light on the underlying pathomechanism of CLL.

CpG island methylation patterns in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is the most common leukemia in Western countries. In CLL, a large number of genes affecting cancer-related pathways may be dysregulated by epigenetic silencing. We analysed by methylation-specific polymerase chain reaction the CpG island methylation status of 15 well-characterised cancer-related genes in 32 patients with CLL. Aberrant methylation in the sample of patients with CLL was shown for secreted frizzled-related protein 1 (68.8%), secreted frizzled-related protein 2 (65.6%), death-associated protein kinase 1 (50.0%), E-cadherin (21.9%), secreted frizzled-related protein 4 (15.6%), p15 (9.4%), p16 (6.3%), retinoic acid receptor beta2 (3.1%), secreted frizzled-related protein 5 (3.1%) and tissue inhibitor of matrix metalloproteinases 3 (3.1%). For human Mut-L homolog 1, O(6)-methylguanine DNA methyltransferase, p73, suppressor of cytokine signalling 1 and tissue inhibitor of matrix metalloproteinases 2 no hypermethylation was detected. Hypermethylation of at least one gene was observed in 87.5% of the samples. Our results show that aberrant CpG island methylation affecting cancer-related pathways such as Wnt signalling, regulation of apoptosis, cell cycle control and tissue invasion is a common phenomenon in CLL. Epigenetic disturbances may be involved in the pathogenesis of CLL and thus may provide a molecular rationale for therapeutic approaches.

Diet-induced hepatocellular carcinoma in genetically predisposed mice

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer death worldwide, with approximately 70% of cases resulting from hepatitis B and C viral infections, aflatoxin exposure, chronic alcohol use or genetic liver diseases. The remaining approximately 30% of cases are associated with obesity, type 2 diabetes and related metabolic diseases, although a direct link between these pathologies and HCCs has not been established. We tested the long-term effects of high-fat and low-fat diets on males of two inbred strains of mice and discovered that C57BL/6J but not A/J males were susceptible to non-alcoholic steatohepatitis (NASH) and HCC on a high-fat but not low-fat diet. This strain-diet interaction represents an important model for genetically controlled, diet-induced HCC. Susceptible mice showed morphological characteristics of NASH (steatosis, hepatitis, fibrosis and cirrhosis), dysplasia and HCC. mRNA profiles of HCCs versus tumor-free liver showed involvement of two signaling networks, one centered on Myc and the other on NFkappaB, similar to signaling described for the two major classes of HCC in humans. miRNA profiles revealed dramatically increased expression of a cluster of miRNAs on the X chromosome without amplification of the chromosomal segment. A switch from high-fat to low-fat diet reversed these outcomes, with switched C57BL/6J males being lean rather than obese and without evidence for NASH or HCCs at the end of the study. A similar diet modification may have important implications for prevention of HCCs in humans.

Src homology 2 domain-containing inositol-5-phosphatase and CCAAT enhancer-binding protein beta are targeted by miR-155 in B cells of Emicro-MiR-155 transgenic mice

We showed that Emicro-MiR-155 transgenic mice develop acute lymphoblastic leukemia/high-grade lymphoma. Most of these leukemias start at approximately 9 months irrespective of the mouse strain. They are preceded by a polyclonal pre-B-cell proliferation, have variable clinical presentation, are transplantable, and develop oligo/monoclonal expansion. In this study, we show that in these transgenic mice the B-cell precursors have the highest MiR-155 transgene expression and are at the origin of the leukemias. We determine that Src homology 2 domain-containing inositol-5-phosphatase (SHIP) and CCAAT enhancer-binding protein beta (C/EBPbeta), 2 important regulators of the interleukin-6 signaling pathway, are direct targets of MiR-155 and become gradually more down-regulated in the leukemic than in the preleukemic mice. We hypothesize that miR-155, by down-modulating Ship and C/EBPbeta, initiates a chain of events that leads to the accumulation of large pre-B cells and acute lymphoblastic leukemia/high-grade lymphoma.

Regulation of MicroRNA Biogenesis: A miRiad of mechanisms

microRNAs are small, non-coding RNAs that influence diverse biological functions through the repression of target genes during normal development and pathological responses. Widespread use of microRNA arrays to profile microRNA expression has indicated that the levels of many microRNAs are altered during development and disease. These findings have prompted a great deal of investigation into the mechanism and function of microRNA-mediated repression. However, the mechanisms which govern the regulation of microRNA biogenesis and activity are just beginning to be uncovered. Following transcription, mature microRNA are generated through a series of coordinated processing events mediated by large protein complexes. It is increasingly clear that microRNA biogenesis does not proceed in a 'one-size-fits-all' manner. Rather, individual classes of microRNAs are differentially regulated through the association of regulatory factors with the core microRNA biogenesis machinery. Here, we review the regulation of microRNA biogenesis and activity, with particular focus on mechanisms of post-transcriptional control. Further understanding of the regulation of microRNA biogenesis and activity will undoubtedly provide important insights into normal development as well as pathological conditions such as cardiovascular disease and cancer.

MicroRNA expression profiling in bone marrow: implications in hematological malignancies

MicroRNA (miRNA) have been recently attributed a crucial role in the control of gene expression in numerous physiological and pathological processes including growth, differentiation and even oncogenesis. Besides detailed mechanistic studies on their generation and function, there has been a great deal of interest in the study of miRNA as surrogate markers of disease. Numerous studies have attempted to define miRNA profiles as predictors of disease outcome, or for the classification/diagnosis of different pathologies. In the present review, we summarize the main studies describing the involvement of miRNA in bone marrow (BM) diseases and in normal BM function during hematopoiesis.

Downregulation of miRNA-200c links breast cancer stem cells with normal stem cells

Human breast tumors contain a breast cancer stem cell (BCSC) population with properties reminiscent of normal stem cells. We found 37 microRNAs that were differentially expressed between human BCSCs and nontumorigenic cancer cells. Three clusters, miR-200c-141, miR-200b-200a-429, and miR-183-96-182 were downregulated in human BCSCs, normal human and murine mammary stem/progenitor cells, and embryonal carcinoma cells. Expression of BMI1, a known regulator of stem cell self-renewal, was modulated by miR-200c. miR-200c inhibited the clonal expansion of breast cancer cells and suppressed the growth of embryonal carcinoma cells in vitro. Most importantly, miR-200c strongly suppressed the ability of normal mammary stem cells to form mammary ducts and tumor formation driven by human BCSCs in vivo. The coordinated downregulation of three microRNA clusters and the similar functional regulation of clonal expansion by miR-200c provide a molecular link that connects BCSCs with normal stem cells.

MicroRNAs in common diseases and potential therapeutic applications

1. Evidence gathered in recent years has revealed microRNAs (miRNAs) fine-tune gene expression and play an important role in various cellular processes, including cell growth, differentiation, proliferation and apoptosis. 2. The present review summarizes current knowledge of miRNA pathways in the pathogenesis of cancer, cardiac diseases, neurodegenerative diseases, diabetes, autoimmune/inflammatory diseases and infection. 3. There is considerable potential to target miRNAs as a novel approach in the treatment of human diseases. Currently, miRNA-based therapies are being examined in both animal models and human clinical trials.

miRò: a miRNA knowledge base

miRò is a web-based knowledge base that provides users with miRNA-phenotype associations in humans. It integrates data from various online sources, such as databases of miRNAs, ontologies, diseases and targets, into a unified database equipped with an intuitive and flexible query interface and data mining facilities. The main goal of miRò is the establishment of a knowledge base which allows non-trivial analysis through sophisticated mining techniques and the introduction of a new layer of associations between genes and phenotypes inferred based on miRNAs annotations. Furthermore, a specificity function applied to validated data highlights the most significant associations. The miRò web site is available at: http://ferrolab.dmi.unict.it/miro.Database URL:http://ferrolab.dmi.unict.it/miro.

MicroRNA expression profile in non-cancerous colonic tissue associated with lymph node metastasis of colon cancer

OBJECTIVE

To identify microRNA expression patterns associated with the lymph node metastasis of colon cancer.

METHODS

MicroRNA were isolated from six frozen non-cancerous surrounding colonic tissues derived from stage II-III colon cancer patients with (n = 3) and without (n = 3) lymph node metastasis. We compared the microRNA expression profiles of the six non-cancerous colonic tissues from two colon cancer patient groups; those with confirmed lymph node metastasis, termed the lymph node positive group, and those without detectable lymph node metastasis, termed the lymph node negative group. MicroRNA expression was analyzed with Agilent microarrays containing 723 human microRNA probes. We validated the expression level of differentially expressed microRNA using quantitative real-time PCR analysis.

RESULTS

Two microRNA (hsa-miR-129*, hsa-miR-137) were differentially expressed in the lymph node positive group compared with the lymph node negative group. The expression level of hsa-miR-137 was quantified via quantitative real-time PCR analysis for validation. Hsa-miR-137 expression was significantly upregulated nearly 6.6-fold in lymph node positive specimens (P = 0.036). The quantitative real-time PCR result correlates with the microarray finding.

CONCLUSION

The non-cancerous colonic tissues from colon cancer patients with lymph node metastasis have a significantly different microRNA expression profile compared to that from colon cancer patients without lymph node metastasis. The differentially expressed microRNA could have relevance to the lymph node metastasis of colon cancer and may provide a simple profiling method to assist in identifying patients with lymph node metastasis. Besides, these data might offer new ideas for preventing and controlling lymphatic metastasis in colon cancer.

Emerging roles of microRNAs as molecular switches in the integrated circuit of the cancer cell

Transformation of normal cells into malignant tumors requires the acquisition of six hallmark traits, e.g., self-sufficiency in growth signals, insensitivity to antigrowth signals and self-renewal, evasion of apoptosis, limitless replication potential, angiogenesis, invasion, and metastasis, which are common to all cancers (Hanahan and Weinberg 2000). These new cellular traits evolve from defects in major regulatory microcircuits that are fundamental for normal homeostasis. The discovery of microRNAs (miRNAs) as a new class of small non-protein-coding RNAs that control gene expression post-transcriptionally by binding to various mRNA targets suggests that these tiny RNA molecules likely act as molecular switches in the extensive regulatory web that involves thousands of transcripts. Most importantly, accumulating evidence suggests that numerous microRNAs are aberrantly expressed in human cancers. In this review, we discuss the emergent roles of microRNAs as switches that function to turn on/off known cellular microcircuits. We outline recent compelling evidence that deregulated microRNA-mediated control of cellular microcircuits cooperates with other well-established regulatory mechanisms to confer the hallmark traits of the cancer cell. Furthermore, these exciting insights into aberrant microRNA control in cancer-associated circuits may be exploited for cancer therapies that will target deregulated miRNA switches.

MicroRNAs as New Players for Diagnosis, Prognosis, and Therapeutic Targets in Breast Cancer

MicroRNAs are small nonprotein-coding RNAs that regulate the expressions of a wide variety of genes by sequence-specific base pairing on the 3′UTR of mRNA targets resulting in mRNA degradation or inhibition of translation. Aberrant expressions of miRNAs have been linked to tumor development, metastasis, diagnosis, prognosis, and therapy response in human breast cancer. Some miRNAs have been considered to have potential clinical applications as a tool for breast cancer prognosis and therapy. Here we describe and discuss lines of evidence supporting the important relationship between miRNAs and breast cancer, and its therapeutic strategies.