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

MiRNAs and cancer

Cancer is the result of a complex multistep process that involves the accumulation of sequential alterations of several genes, including those encoding microRNAs (miRNAs). miRNAs are a class of 17- to 27-nucleotide single-stranded RNA molecules that regulate gene expression posttranscriptionally. A large body of evidence implicates aberrant miRNA expression patterns in most, if not all, human malignancies. This article reviews our current knowledge about miRNAs, focusing on their involvement in cancer and their potential as diagnostic, prognostic, and therapeutic tools.

MicroRNA polymorphisms: a giant leap towards personalized medicine

"An individual's genetic inheritance of microRNA polymorphisms associated with disease progression, prognosis and treatment holds the key to create safer and more personalized drugs and can be a giant leap towards personalized medicine."

MicroRNA polymorphisms: the future of pharmacogenomics, molecular epidemiology and individualized medicine

Referred to as the micromanagers of gene expression, microRNAs (miRNAs) are evolutionarily conserved small noncoding RNAs. Polymorphisms in the miRNA pathway (miR-polymorphisms) are emerging as powerful tools to study the biology of a disease and have the potential to be used in disease prognosis and diagnosis. Detection of miR-polymorphisms holds promise in the field of miRNA pharmacogenomics, molecular epidemiology and for individualized medicine. MiRNA pharmacogenomics can be defined as the study of miRNAs and polymorphisms affecting miRNA function in order to predict drug behavior and to improve drug efficacy. Advancements in the miRNA field indicate the clear involvement of miRNAs and genetic variations within the miRNA pathway in the progression and prognosis of diseases such as cancer, neurological disorders, muscular hypertrophy, gastric mucosal atrophy, cardiovascular disease and Type II diabetes. Various algorithms are available to predict miRNA-target mRNA sites; however, it is advisable to use multiple algorithms to confirm the predictions. Polymorphisms that may potentially affect miRNA-mediated regulation of the cell can be present not only in the 3 -UTR of a miRNA target gene, but also in the genes involved in miRNA biogenesis and in pri-, pre- and mature-miRNA sequences. A polymorphism in processed miRNAs may affect expression of several genes and have serious consequences, whereas a polymorphism in miRNA target site, in the 3 -UTR of the target mRNA, may be more target and/or pathway specific. In this review, we for the first time suggest a classification of miRNA polymorphisms/mutations. We also describe the importance and implications of miR-polymorphisms in gene regulation, disease progression, pharmacogenomics and molecular epidemiology.

MicroRNAs: novel biomarkers for human cancer

BACKGROUND

MicroRNAs (miRNAs), small RNA molecules of approximately 22 nucleotides, have been shown to be up- or downregulated in specific cell types and disease states. These molecules have become recognized as one of the major regulatory gatekeepers of coding genes in the human genome.

CONTENT

We review the structure, nomenclature, mechanism of action, technologies used for miRNA detection, and associations of miRNAs with human cancer. miRNAs are produced in a tissue-specific manner, and changes in miRNA within a tissue type can be correlated with disease status. miRNAs appear to regulate mRNA translation and degradation via mechanisms that are dependent on the degree of complementarity between the miRNA and mRNA molecules. miRNAs can be detected via several methods, such as microarrays, bead-based arrays, and quantitative real-time PCR. The tissue concentrations of specific miRNAs have been associated with tumor invasiveness, metastatic potential, and other clinical characteristics for several types of cancers, including chronic lymphocytic leukemia, and breast, colorectal, hepatic, lung, pancreatic, and prostate cancers.

SUMMARY

By targeting and controlling the expression of mRNA, miRNAs can control highly complex signal-transduction pathways and other biological pathways. The biologic roles of miRNAs in cancer suggest a correlation with prognosis and therapeutic outcome. Further investigation of these roles may lead to new approaches for the categorization, diagnosis, and treatment of human cancers.

MicroRNAs and cancer: short RNAs go a long way

MicroRNAs (miRNAs) may be important regulators of gene expression. By modulating oncogenic and tumor suppressor pathways they could, in principle, contribute to tumorigenesis. Consistent with this hypothesis, recurrent genetic and epigenetic alterations of individual miRNAs are found in some tumors. Functional studies are now elucidating the mechanism of action of putative oncogenic and tumor suppressor miRNAs.

Targeted therapy: comprehensive review

The National Hospice and Palliative Care Organization estimates that in 2006, 44.1% of hospice admissions had cancer as primary diagnosis, still representing the most common diagnosis in this level of care. In the recent years, the treatment of cancer sustained unprecedented advances with better understanding of cancer biology. Growth factor receptors emerged as target for effective therapy providing significant clinical benefit, for example epidermal growth factor receptor 2 or human epidermal growth factor receptor 2 + breast cancer disease has been routinely treated with trastuzumab, a monoclonal antibody, with significant survival benefit. Other cancers had their treatment changed by targeted therapy. This article reviews concepts of cancer cell biology and analyze the current standard of care use of targeted therapy. The data highlights aspects of targeted therapy important to health care professionals involved in hospice and palliative care of patients with cancer.

MicroRNAs as biomarkers and therapeutic drugs in human cancer

MicroRNAs (miRNAs) are evolutionarily conserved, endogenous, noncoding small RNAs that act as post-transcriptional gene regulators. Experimental evidence has shown that miRNAs can play roles as oncogenes or tumor suppressor genes, suggesting their contribution to cancer development and progression. Expression profiles of human miRNAs demonstrated that many miRNAs are deregulated in cancers and are differentially expressed in normal tissues and cancers. Therefore, miRNA profiling is used to create signatures for a variety of cancers, indicating that the profile will help further establish molecular diagnosis, prognosis and therapy using miRNAs. This paper introduces the aberrant expression of miRNAs in human cancer, and discusses the potential of these miRNAs as biomarkers and targets/molecules for molecular therapy.

Patterns of microRNA expression characterize stages of human B-cell differentiation

Mature B-cell differentiation provides an important mechanism for the acquisition of adaptive immunity. Malignancies derived from mature B cells constitute the majority of leukemias and lymphomas. These malignancies often maintain the characteristics of the normal B cells that they are derived from, a feature that is frequently used in their diagnosis. The role of microRNAs in mature B cells is largely unknown. Through concomitant microRNA and mRNA profiling, we demonstrate a potential regulatory role for microRNAs at every stage of the mature B-cell differentiation process. In addition, we have experimentally identified a direct role for the microRNA regulation of key transcription factors in B-cell differentiation: LMO2 and PRDM1 (Blimp1). We also profiled the microRNA of B-cell tumors derived from diffuse large B-cell lymphoma, Burkitt lymphoma, and chronic lymphocytic leukemia. We found that, in contrast to many other malignancies, common B-cell malignancies do not down-regulate microRNA expression. Although these tumors could be distinguished from each other with use of microRNA expression, each tumor type maintained the expression of the lineage-specific microRNAs. Expression of these lineage-specific microRNAs could correctly predict the lineage of B-cell malignancies in more than 95% of the cases. Thus, our data demonstrate that microRNAs may be important in maintaining the mature B-cell phenotype in normal and malignant B cells.

Prognostic value of miR-16 expression in childhood acute lymphoblastic leukemia relationships to normal and malignant lymphocyte proliferation

miR-16, a miRNA involved in cell proliferation and apoptosis regulation, may interfere with either oncogenic or tumor-suppressor pathways and is implicated in leukemogenesis. We then explored its expression in 93 childhood acute lymphoblastic leukemia (ALL) cases. A high miR-16 expression was associated with hyperleukocytosis and poor cytogenetic groups. In the whole group and in B-cell ALLs, disease-free survival (DFS) was significantly shorter for miR-16 above quartile 75. In T-cell ALLs, for both DFS and overall survival, a significant trend was found with a survival shortening from the lowest to the highest miR-16 levels. miR-16 expression neither significantly correlated with normal and malignant lymphocyte proliferation nor varied according to lymphocyte differentiation. The prognostic value of miR-16 in childhood ALL highlighted the complexity of miR-16 functions.

Identification of forensically relevant body fluids using a panel of differentially expressed microRNAs

The serology-based methods routinely used in forensic casework for the identification of biological fluids are costly in terms of time and sample and have varying degrees of sensitivity and specificity. Recently, the use of a molecular genetics-based approach using messenger RNA (mRNA) profiling has been proposed to supplant conventional methods for body fluid identification. However, the size of the amplification products used in these mRNA assays (approximately 200-300 nt) might not be ideal for use with degraded or compromised samples frequently encountered in forensic casework. Recently, there has been an explosion of interest in a novel class of small noncoding RNAs, microRNAs (miRNAs, approximately 20-25 bases in length), with numerous published studies reporting that some miRNAs are expressed in a tissue-specific manner. In this article, we provide the first comprehensive evaluation of miRNA expression in dried, forensically relevant biological fluids--blood, semen, saliva, vaginal secretions, and menstrual blood--in an attempt to identify putative body fluid-specific miRNAs. Most of the 452 human miRNAs tested (approximately 67% of the known miRNAome) were either expressed in multiple body fluids or not expressed at all. Nevertheless, we have identified a panel of nine miRNAs--miR451, miR16, miR135b, miR10b, miR658, miR205, miR124a, miR372, and miR412--that are differentially expressed to such a degree as to permit the identification of the body fluid origin of forensic biological stains using as little as 50 pg of total RNA. The miRNA-based body fluid identification assays were highly specific because the miRNA expression profile for each body fluid was different from that obtained from 21 human tissues. The results of this study provide an initial indication that miRNA profiling may provide a promising alternative approach to body fluid identification for forensic casework.

Down-regulation of hsa-miR-10a in chronic myeloid leukemia CD34+ cells increases USF2-mediated cell growth

MicroRNAs (miRNA) are small noncoding, single-stranded RNAs that inhibit gene expression at a posttranscriptional level, whose abnormal expression has been described in different tumors. The aim of our study was to identify miRNAs potentially implicated in chronic myeloid leukemia (CML). We detected an abnormal miRNA expression profile in mononuclear and CD34(+) cells from patients with CML compared with healthy controls. Of 157 miRNAs tested, hsa-miR-10a, hsa-miR-150, and hsa-miR-151 were down-regulated, whereas hsa-miR-96 was up-regulated in CML cells. Down-regulation of hsa-miR-10a was not dependent on BCR-ABL1 activity and contributed to the increased cell growth of CML cells. We identified the upstream stimulatory factor 2 (USF2) as a potential target of hsa-miR-10a and showed that overexpression of USF2 also increases cell growth. The clinical relevance of these findings was shown in a group of 85 newly diagnosed patients with CML in which expression of hsa-miR-10a was down-regulated in 71% of the patients, whereas expression of USF2 was up-regulated in 60% of the CML patients, with overexpression of USF2 being significantly associated with decreased expression of hsa-miR-10a (P = 0.004). Our results indicate that down-regulation of hsa-miR-10a may increase USF2 and contribute to the increase in cell proliferation of CML implicating a miRNA in the abnormal behavior of CML.

Potentially important microRNA cluster on chromosome 17p13.1 in primary peritoneal carcinoma

MicroRNAs are a group of small non-coding RNAs approximately 22 nucleotides in length. Recent work has shown differential expression of mature microRNAs in human cancers. We characterized the alteration in expression of a select group of microRNAs in primary peritoneal carcinoma relative to matched cases of ovarian serous carcinoma. MicroRNA expression was analysed using semi-quantitative stem-loop RT-PCR on a set of 34 formalin-fixed paraffin-embedded samples. Protein expression of p53 and bcl-2 was quantified in the corresponding tissue microarray. We provide definitive evidence that there is downregulation of a select group of microRNAs in tumours meeting Gynaecological Oncology Group criteria for primary peritoneal carcinoma relative to ovarian serous carcinoma. Specifically, we show decreased p53 expression and downregulation of miR-195 and miR-497 from the microRNA cluster site at chromosome 17p13.1 in primary peritoneal carcinoma relative to ovarian serous carcinoma. miR-195 and miR-497 may have potential roles as tumour-suppressor genes in primary peritoneal tumourigenesis.

Over-expressed microRNA-27a and 27b influence fat accumulation and cell proliferation during rat hepatic stellate cell activation

Hepatic stellate cells (HSCs) activation is an initial event in liver fibrosis. MicroRNAs (miRNAs) have been found to play essential roles in cell differentiation, proliferation, and fat metabolism. In this study, we showed that down-regulation of two over-expressed miRNAs, miR-27a and 27b allowed culture-activated rat HSCs to switch to a more quiescent HSC phenotype, with restored cytoplasmic lipid droplets and decreased cell proliferation. Mechanistically, retinoid X receptor alpha was confirmed to be the target of miR-27a and 27b. These results indicated a new role and mechanism of miR-27a and 27b in regulating fat metabolism and cell proliferation during HSCs activation.

Novel genetic variants in microRNA genes and familial breast cancer

MicroRNA (miRNA) plays an important role in tumorigenesis, but whether miRNA is a cancer predisposition factor or not is still unknown. Considering the fact that miRNA regulates a number of tumor suppressor genes (TSGs) and oncogenes, genetic variations in miRNA genes could affect the levels of expression of TSGs or oncogenes and, thereby, cancer risk. To test this hypothesis, we screened genetic variants in 17 selected miRNA genes, which are predicted to regulate key breast cancer genes, in 42 patients with familial breast cancer. Seven novel genetic variants were observed in 7 primary or precursor miRNA genes. Among them, 1 rare variant in the precursor of miR-30c-1 and 1 rare variant in the primary precursor of miR-17 were only observed in noncarriers of BRCA1/2 mutations. In functional assays, these 2 variants resulted in conformational changes in the predicted secondary structures, and consequently altered the expression of mature miR-30c-1 and miR-17. In the target in vitro assay, we observed that miR-17 could bind to the 3'UTR of BRCA1 mRNAs, which is predicted to be a target for miR-17. Our findings suggest that functional genetic variants in miRNA genes can potentially alter the regulation of key breast cancer genes. Whether they confer genetic susceptibility to breast cancer remains to be determined.

MicroRNA-101, down-regulated in hepatocellular carcinoma, promotes apoptosis and suppresses tumorigenicity

Although aberrant microRNA (miRNA) expressions have been observed in different types of cancer, their pathophysiologic role and their relevance to tumorigenesis are still largely unknown. In this study, we first evaluated the expression of 308 miRNAs in human hepatocellular carcinoma (HCC) and normal hepatic tissues and identified 29 differentially expressed miRNAs in HCC tissues. miR-101, a significantly down-regulated miRNA, was further studied in greater detail because the signal pathway(s) regulated by miR-101 and the role of miR-101 in tumorigenesis have not yet been elucidated. Interestingly, decreased expression of miR-101 was found in all six hepatoma cell lines examined and in as high as 94.1% of HCC tissues, compared with their nontumor counterparts. Furthermore, ectopic expression of miR-101 dramatically suppressed the ability of hepatoma cells to form colonies in vitro and to develop tumors in nude mice. We also found that miR-101 could sensitize hepatoma cell lines to both serum starvation- and chemotherapeutic drug-induced apoptosis. Further investigation revealed that miR-101 significantly repressed the expression of luciferase carrying the 3'-untranslated region of Mcl-1 and reduced the endogenous protein level of Mcl-1, whereas the miR-101 inhibitor obviously up-regulated Mcl-1 expression and inhibited cell apoptosis. Moreover, silencing of Mcl-1 phenocopied the effect of miR-101 and forced expression of Mcl-1 could reverse the proapoptotic effect of miR-101. These results indicate that miR-101 may exert its proapoptotic function via targeting Mcl-1. Taken together, our data suggest an important role of miR-101 in the molecular etiology of cancer and implicate the potential application of miR-101 in cancer therapy.

The role of microRNA in human leukemia: a review

MicroRNAs (miRNAs or miRs) are 18-22-nucleotide non-coding RNAs that have emerged as a new paradigm of epigenetic regulation in both normal development and cellular function, and in the pathogenesis of human disease including cancer. This review summarizes the current literature of mechanism of gene regulation by miRNA and their role in hematopoiesis and leukemogenesis. An understanding of these processes suggests further avenues for research to understand gene regulation and miRNA-based therapeutic approaches.

microRNA-29c and microRNA-223 down-regulation has in vivo significance in chronic lymphocytic leukemia and improves disease risk stratification

Aberrant expression of microRNAs has been recently associated with chronic lymphocytic leukemia (CLL) outcome. Although disease evolution can be predicted by several prognostic factors, a better outcome individualization in a given patient is still of utmost interest. Here, we showed that miR-29c and miR-223 expression levels decreased significantly with progression from Binet stage A to C were significantly lower in poor prognostic subgroups (defined by several prognostic factors) and could significantly predict treatment-free survival (TFS) and overall survival (OS). Furthermore, we developed a quantitative real-time polymerase chain reaction (qPCR) score combining miR-29c, miR-223, ZAP70, and LPL (from 0 to 4 poor prognostic markers) to stratify treatment and death risk in a cohort of 110 patients with a median follow-up of 72 months (range, 2-312). Patients with a score of 0/4, 1/4, 2/4, 3/4, and 4/4 had a median TFS of greater than 312, of 129, 80, 36, and 19 months, respectively (hazard ratio, HR(0/4 < 1/4 < 2/4 < 3/4 < 4/4) = 17.00, P < .001). Patients with a score of 0-1/4, 2-3/4, and 4/4 had a median OS of greater than 312, of 183 and 106 months, respectively (HR(0/4 < 1/4 < 2/4 < 3/4 < 4/4) = 13.69, P = .001). This score will help to identify, among the good and poor prognosis subgroups, patients who will need early therapy and thus will require a closer follow-up.

MicroRNA-15b regulates cell cycle progression by targeting cyclins in glioma cells

MicroRNAs (miRNAs) are non-protein-coding RNAs that function as post-transcriptional gene regulators. Recent evidence has shown that miRNA plays a pivotal role in the development of many cancers including glioma, a lethal brain cancer. We have recently compared the miRNA expression profiles between normal brain and glioma tissues from Chinese patients by miRNA microarray and identified a panel of differentially expressed miRNAs. Here, we studied the function of one miRNA, miR-15b, in glioma carcinogenesis and elucidated its downstream targets. Over-expression of miR-15b resulted in cell cycle arrest at G0/G1 phase while suppression of miR-15b expression resulted in a decrease of cell populations in G0/G1 and a corresponding increase of cell populations in S phase. We further showed that CCNE1 (encoding cyclin E1) is one of the downstream targets of miR-15b. Taken together, our findings indicate that miR-15b regulates cell cycle progression in glioma cells by targeting cell cycle-related molecules.

The role of cytogenetic abnormalities as a prognostic marker in primary myelofibrosis: applicability at the time of diagnosis and later during disease course

Although cytogenetic abnormalities are important prognostic factors in myeloid malignancies, they are not included in current prognostic scores for primary myelofibrosis (PMF). To determine their relevance in PMF, we retrospectively examined the impact of cytogenetic abnormalities and karyotypic evolution on the outcome of 256 patients. Baseline cytogenetic status impacted significantly on survival: patients with favorable abnormalities (sole deletions in 13q or 20q, or trisomy 9 +/- one other abnormality) had survivals similar to those with normal diploid karyotypes (median, 63 and 46 months, respectively), whereas patients with unfavorable abnormalities (rearrangement of chromosome 5 or 7, or > or = 3 abnormalities) had a poor median survival of 15 months. Patients with abnormalities of chromosome 17 had a median survival of only 5 months. A model containing karyotypic abnormalities, hemoglobin, platelet count, and performance status effectively risk-stratified patients at initial evaluation. Among 73 patients assessable for clonal evolution during stable chronic phase, those who developed unfavorable or chromosome 17 abnormalities had median survivals of 18 and 9 months, respectively, suggesting the potential role of cytogenetics as a risk factor applicable at any time in the disease course. Dynamic prognostic significance of cytogenetic abnormalities in PMF should be further prospectively evaluated.

Genetic analysis of cancer-implicated MicroRNA in ovarian cancer

PURPOSE

There is accumulating evidence that microRNAs may function like classic tumor suppressor genes but little is known about their mechanism of inactivation in cancer cells. We investigated whether somatic mutations are a common mechanism of inactivation of microRNA genes in ovarian cancer.

EXPERIMENTAL DESIGN

Ten cancer-implicated microRNA genes were analyzed for somatic mutations in 90 ovarian epithelial cancers and matching normal DNA. High-resolution melt analysis and bidirectional sequencing was used to detect sequence variations.

RESULTS

High-resolution melt analysis and direct sequencing did not identify any somatic mutations but did reveal numerous novel and previously reported germ line base substitutions, deletions, and insertions surrounding the mature microRNA sequences. The majority of variants were detected in the same proportion of non-cancer control individuals suggesting that they do not represent ovarian cancer-predisposing alleles.

CONCLUSION

The absence of somatic mutations in any of the 10 cancer-implicated microRNAs in our large cohort of ovarian tumors suggests that this may be an uncommon mechanism of inactivation of microRNAs in ovarian cancer.

miRNAs: from biogenesis to networks

In eukaryotes, besides alternative splicing and promoter regulation of "classical" genes, there is also another level of genetic regulation based on non-coding RNAs (ncRNAs). The most famous group of ncRNAs is microRNAs, probably the biggest number of genome regulators. Here, we summarize the knowledge that has been accumulated about the microRNA field, focusing our attention on brief history, biogenesis, regulated mechanism, computational methods of miRNA finding and miRNA target sites, miRNAs and diseases, and miRNAs and network analysis.

Multiple approach to analyzing the role of microRNAs in apoptosis

MicroRNAs (miRNAs) are noncoding RNAs whose hallmarks are the very short sequences and the ability to repress the translation and/or transcription of target genes. miRNAs can have diverse functions, including regulation of cellular differentiation, proliferation, and embryogenesis. Over the past 5 years, an increasing number of studies have linked different miRNAs with programmed cell death or apoptosis. The principal aim of this chapter is to describe a method that (1) identifies miRNAs involved in apoptosis, using a validated array profiling approach, (2) assesses the direct involvement of candidate miRNAs in apoptosis, and (3) identifies the molecular mechanisms possibly involved in apoptotic response. To disclose the possible molecular targets of miRNAs, we propose the generation of a database created using a list of presumptive miRNA targets and the changes in the transcriptome after ectopic expression of the miRNAs. Our proposed method for doing this is suitable for both discovery of apoptotic pathways that regulate miRNAs and finding new miRNAs able to induce apoptosis.

MicroRNAs in cancer

Within the past few years, studies on microRNA (miRNA) and cancer have burst onto the scene. Profiling of the miRNome (global miRNA expression levels) has become prevalent, and abundant miRNome data are currently available for various cancers. The pattern of miRNA expression can be correlated with cancer type, stage, and other clinical variables, so miRNA profiling can be used as a tool for cancer diagnosis and prognosis. miRNA expression analyses also suggest oncogenic (or tumor-suppressive) roles of miRNAs. miRNAs play roles in almost all aspects of cancer biology, such as proliferation, apoptosis, invasion/metastasis, and angiogenesis. Given that many miRNAs are deregulated in cancers but have not yet been further studied, it is expected that more miRNAs will emerge as players in the etiology and progression of cancer. Here we also discuss miRNAs as a tool for cancer therapy.

Identification of miRNAs associated with tumorigenesis of retinoblastoma by miRNA microarray analysis

INTRODUCTION

MicroRNAs (miRNAs) are small (approximately 22 nucleotides) regulatory RNAs which play fundamental roles in many human diseases, including cancer. There is no report on the miRNA expression profile of retinoblastoma.

METHODS

This work was undertaken to identify differentially expressed miRNAs in human retinoblastoma tissues by microRNA microarray technique, and some miRNAs were verified using northern blot analysis and the in situ hybridization method.

RESULTS

A cluster of microRNAs was identified as highly expressed in retinoblastoma, including hsa-miR-494, hsa-let-7e, hsa-miR-513-1, hsa-miR-513-2, hsa-miR-518c*, hsa-miR-129-1, hsa-miR-129-2, hsa-miR-198, hsa-miR-492, hsa-miR-498, hsa-miR-320, hsa-miR-503, and hsa-miR-373*.

CONCLUSION

These miRNAs are the first to be reported for human retinoblastoma and may play significant roles in regulating tumor genesis.

Expression profile of microRNA in epithelial cancer: diagnosis, classification and prediction

BACKGROUND

MicroRNAs (miRNAs), the small non-coding RNAs, regulate gene expression in a sequence-specific manner. Up to one-third of human messenger RNAs (mRNAs) appear to be miRNA targets. Each miRNA can target hundreds of mRNA transcripts and production of proteins directly or indirectly, while more than one miRNA can converge on a single transcript target. Therefore, potential regulatory circuitries afforded by miRNAs are enormous. Recent studies indicate that miRNAs act as key regulators of various fundamental biological processes, in which common pathways are shared with cancer.

OBJECTIVE/METHODS

To provide an overview of the potential application of miRNA profile in human epithelial cancer diagnosis, more than 180 miRNA-related publications have been reviewed.

CONCLUSION

Increasing evidence shows that the expression of miRNAs is remarkably deregulated in human cancer owing to multiple epigenetic and genomic alterations, and several miRNAs have been demonstrated to serve as tumor suppressor genes or oncogenes in cancer. The deregulated miRNA expression profile in human cancer may prove a powerful tool for cancer detection, diagnosis, classification and prognosis.

Expression of microRNAs in diffuse large B cell lymphoma is associated with immunophenotype, survival and transformation from follicular lymphoma

MicroRNAs are naturally occurring small RNA species that regulate gene expression and are frequently abnormally expressed in cancers. However, the role of microRNAs in lymphoma is poorly understood. Therefore, we undertook a comprehensive study of microRNA expression in two of the most common lymphomas: diffuse large B-cell lymphoma (DLBCL) (n= 80) and follicular lymphoma (FCL) (n= 18) using microarrays containing probes for 464 human microRNAs. Unsupervised cluster analysis revealed distinct expression patterns between these two lymphomas and specific microRNA signatures (including members of the miR-17–92 cluster) were derived that correctly predicted lymphoma type in >95% of cases. Furthermore, we identified microRNAs in de novo DLBCL (n= 64) associated with germinal centre-like and non-germinal centre-like immunophenotypes, international prognostic index status and event-free survival in CHOP and rituximab (R)-CHOP treated patients. Despite the indolent nature of FCL a significant proportion of cases undergo high-grade transformation to more aggressive DLBCL. In order to see if transformation is associated with changes in microRNA expression we compared transformed DLBCL cases (n= 16) with de novo DLBCL, as well as FCL cases that underwent subsequent transformation (n= 7) with FCL cases that had not transformed at a median follow-up of 60 months (n= 11). Differential expression of 12 microRNAs correctly predicted >85% of transformed versus de novo DLBCL cases; six microRNAs (miR-223, 217, 222, 221 and let-7i and 7b) were found which could similarly predict or transformation in FCL (P< 0.05). These data suggest that microRNAs have potential as diagnostic and prognostic markers in these lymphomas and may be used to identify FCL patients at risk of high-grade transformation.

How to use clinical vignettes in hematology--a pilot survey in the context of chronic lymphocytic leukemia

RATIONALE

Case vignettes have been validated as an efficient tool for assessing the quality of clinical practices, and have been used in a variety of medical settings. However, their use in the field of hematology has not been tested.

OBJECTIVES

We undertook a study to pre-test seven case vignettes, and thereby to assess practice patterns and, when possible, guideline adherence in the treatment of chronic lymphocytic leukemia (CLL) by French hematologists.

FINDINGS

Of the 64 hematologists who agreed to participate, 26 (41%) completed the vignettes. We found significant differences in the physicians' patterns of ordering further investigations among young and old patients in the same clinical context. This is not consistent with published guidelines. Moreover, the most striking differences concerned the physicians' interpretations of prognostic factors and the use of radiological testing before treatment. Modalities of treatment were variable across clinical situations, especially with regard to second-line treatments. Clinicians understood the vignettes well, except for those that dealt with stem cell transplantation.

CONCLUSIONS

This pilot study showed the feasibility of the use of case vignettes to assess the quality of clinical practice in CLL. The initial results identified deviations from the published guidelines. A large-scale European survey will commence in a few months.

Cellular versus viral microRNAs in host-virus interaction

MicroRNAs (miRNAs) mark a new paradigm of RNA-directed gene expression regulation in a wide spectrum of biological systems. These small non-coding RNAs can contribute to the repertoire of host-pathogen interactions during viral infection. This interplay has important consequences, both for the virus and the host. There have been reported evidences of host-cellular miRNAs modulating the expression of various viral genes, thereby playing a pivotal role in the host-pathogen interaction network. In the hide-and-seek game between the pathogens and the infected host, viruses have evolved highly sophisticated gene-silencing mechanisms to evade host-immune response. Recent reports indicate that virus too encode miRNAs that protect them against cellular antiviral response. Furthermore, they may exploit the cellular miRNA pathway to their own advantage. Nevertheless, our increasing knowledge of the host-virus interaction at the molecular level should lead us toward possible explanations to viral tropism, latency and oncogenesis along with the development of an effective, durable and nontoxic antiviral therapy. Here, we summarize the recent updates on miRNA-induced gene-silencing mechanism, modulating host-virus interactions with a glimpse of the miRNA-based antiviral therapy for near future.

miR-192 Regulates dihydrofolate reductase and cellular proliferation through the p53-microRNA circuit

PURPOSE

The purpose of this study is to investigate the molecular mechanism of miR-192 in colon cancer.

EXPERIMENTAL DESIGN

Human colon cancer cell lines with different p53 status were used as our model system to study the effect of miR-192 on cell proliferation, cell cycle control, and mechanism of regulation.

RESULTS

Our results show that one of the key miR-192 target genes is dihydrofolate reductase (DHFR). miR-192 affects cellular proliferation through the p53-miRNA circuit. Western immunoblot analyses indicated that the expression of DHFR was significantly decreased by miR-192. Further investigation revealed that such suppression was due to translational arrest rather than mRNA degradation. More profound inhibition of cellular proliferation was observed by ectopic expression of miR-192 in colon cancer cell lines containing wild-type p53 than cells containing mutant p53. Thus, the effect of miR-192 on cellular proliferation is mainly p53 dependent. Overexpression of miR-192 triggered both G1 and G2 arrest in HCT-116 (wt-p53) cells but not in HCT-116 (null-p53) cells. The cell cycle checkpoint control genes p53 and p21 were highly overexpressed in cells that overexpressed miR-192. Endogenous miR-192 expression was increased in HCT-116 (wt-p53) and RKO (wt-p53) cells treated with methotrexate, which caused an induction of p53 expression. Chromatin immunoprecipitation-quantitative reverse transcription-PCR analysis revealed that the p53 protein interacted with the miR-192 promoter sequence.

CONCLUSION

These results indicate that miR-192 may be another miRNA candidate that is involved in the p53 tumor suppressor network with significant effect on cell cycle control and cell proliferation.

MicroRNAs in pancreatic ductal adenocarcinoma: new diagnostic and therapeutic clues

MicroRNAs (miRNAs) are small non-coding RNAs 19-24 nucleotides in length that regulate gene expression of target genes by translational repression. They regulate crucial processes such as development, proliferation, apoptosis, stress response and differentiation. Recent reports support a role for miRNAs in the initiation and progression of human malignancies; in particular, aberrant expression of miRNAs can contribute to carcinogenesis by promoting the expression of proto-oncogenes or by inhibiting the expression of tumor suppressor genes. Large high-throughput studies in patients revealed that miRNA profiling allows classifying tumors with high accuracy and predicting their outcome. In this review, we summarize recent knowledge about miRNA expression in pancreatic ductal adenocarcinoma, their possible molecular implications, and finally, we discuss the possible repercussion of these findings in terms of diagnosis and treatment of this disease.

Single nucleotide polymorphisms of microRNA machinery genes modify the risk of renal cell carcinoma

PURPOSE

MicroRNAs (miRNA) are a class of small noncoding RNA molecules that have been implicated in a wide variety of basic cellular functions through posttranscriptional regulations on their target genes. Compelling evidence has shown that miRNAs are involved in cancer initiation and progression. We hypothesized that genetic variations of the miRNA machinery genes could be associated with the risk of renal cell carcinoma.

EXPERIMENTAL DESIGN

We genotyped 40 single nucleotide polymorphisms (SNP) from 11 miRNA processing genes (DROSHA, DGCR8, XPO5, RAN, DICER1, TARBP2, AGO1, AGO2, GEMIN3, GEMIN4, HIWI) and 15 miRNA genes in 279 Caucasian patients with renal cell carcinoma and 278 matched controls.

RESULTS

We found that two SNPs in the GEMIN4 gene were significantly associated with altered renal cell carcinoma risks. The variant-containing genotypes of Asn929Asp and Cys1033Arg exhibited significantly reduced risks, with odds ratios (OR) of 0.67 [95% confidence interval (95% CI), 0.47-0.96] and 0.68 (95% CI, 0.47-0.98), respectively. Haplotype analysis showed that a common haplotype of GEMIN4 was associated with a significant reduction in the risk of renal cell carcinoma (OR, 0.66; 95% CI, 0.45-0.97). We also conducted a combined unfavorable genotype analysis including five promising SNPs showing at least a borderline significant risk association. Compared with the low-risk reference group with one unfavorable genotype, the median-risk and high-risk groups exhibited a 1.55-fold (95% CI, 0.96-2.50) and a 2.49-fold (95% CI, 1.58-3.91) increased risk of renal cell carcinoma, respectively (P for trend < 0.001).

CONCLUSIONS

Our results suggested that genetic polymorphisms of the miRNA-machinery genes may affect renal cell carcinoma susceptibility individually and jointly.

Differentiation stage-specific expression of microRNAs in B lymphocytes and diffuse large B-cell lymphomas

miRNAs are small RNA molecules binding to partially complementary sites in the 3'-UTR of target transcripts and repressing their expression. miRNAs orchestrate multiple cellular functions and play critical roles in cell differentiation and cancer development. We analyzed miRNA profiles in B-cell subsets during peripheral B-cell differentiation as well as in diffuse large B-cell lymphoma (DLBCL) cells. Our results show temporal changes in the miRNA expression during B-cell differentiation with a highly unique miRNA profile in germinal center (GC) lymphocytes. We provide experimental evidence that these changes may be physiologically relevant by demonstrating that GC-enriched hsa-miR-125b down-regulates the expression of IRF4 and PRDM1/BLIMP1, and memory B cell-enriched hsa-miR-223 down-regulates the expression of LMO2. We further demonstrate that although an important component of the biology of a malignant cell is inherited from its nontransformed cellular progenitor-GC centroblasts-aberrant miRNA expression is acquired upon cell transformation. A 9-miRNA signature was identified that could precisely differentiate the 2 major subtypes of DLBCL. Finally, expression of some of the miRNAs in this signature is correlated with clinical outcome of uniformly treated DLBCL patients.

Ovarian cancer plasticity and epigenomics in the acquisition of a stem-like phenotype

Aggressive epithelial ovarian cancer (EOC) is genetically and epigenetically distinct from normal ovarian surface epithelial cells (OSE) and early neoplasia. Co-expression of epithelial and mesenchymal markers in EOC suggests an involvement of epithelial-mesenchymal transition (EMT) in cancer initiation and progression. This phenomenon is often associated with acquisition of a stem cell-like phenotype and chemoresistance that correlate with the specific gene expression patterns accompanying transformation, revealing a plasticity of the ovarian cancer cell genome during disease progression.Differential gene expressions between normal and transformed cells reflect the varying mechanisms of regulation including genetic changes like rearrangements within the genome, as well as epigenetic changes such as global genomic hypomethylation with localized promoter CpG island hypermethylation. The similarity of gene expression between ovarian cancer cells and the stem-like ovarian cancer initiating cells (OCIC) are surprisingly also correlated with epigenetic mechanisms of gene regulation in normal stem cells. Both normal and cancer stem cells maintain genetic flexibility by co-placement of activating and/or repressive epigenetic modifications on histone H3. The co-occupancy of such opposing histone marks is believed to maintain gene flexibility and such bivalent histones have been described as being poised for transcriptional activation or epigenetic silencing. The involvement of both-microRNA (miRNA) mediated epigenetic regulation, as well as epigenetic-induced changes in miRNA expression further highlight an additional complexity in cancer stem cell epigenomics.Recent advances in array-based whole-genome/epigenome analyses will continue to further unravel the genomes and epigenomes of cancer and cancer stem cells. In order to illuminate phenotypic signatures that delineate ovarian cancer from their associated cancer stem cells, a priority must lie in the expansion of current technologies and further implementation of bioinformatics to handle the complexity of the cancer epigenome and the various networks that coordinate disease initiation and progression. Great potential lies in the translation of these findings into epigenetic-based therapies. Additionally, targeting chemo-resistant cancer stem cells may provide a much needed breakthrough in treatment of advanced ovarian cancer and chemoresistant disease.

Beyond HPV: oncomirs as new players in cervical cancer

MicroRNAs (miRNAs) are a recently discovered family of 18-24 nucleotide non-coding RNAs that can negatively regulate target mRNAs. All studied multicellular eukaryotes utilize miRNAs to regulate basic cellular functions including proliferation, differentiation, and death. It is now apparent that abnormal miRNA expression is a common feature of human malignancies. This review discusses the various cancer-relevant miRNAs (oncomirs) especially in cervical tumorigenesis and the potential role of oncomirs as therapeutic agents and targets for the treatment of cervical cancer.

Bcl-2 family proteins and cancer

BCL-2 was the first anti-death gene discovered, a milestone with far reaching implications for tumor biology. Multiple members of the human Bcl-2 family of apoptosis-regulating proteins have been identified, including six antiapoptotic, three structurally similar proapoptotic proteins and several structurally diverse proapoptotic interacting proteins that operate as upstream agonists or antagonists. These proteins, in turn, are regulated through myriad post-translational modifications and interactions with other proteins. Bcl-2-family proteins regulate all major types of cell death, including apoptosis, necrosis and autophagy, thus operating as nodal points at the convergence of multiple pathways with broad relevance to oncology. Experimental therapies targeting Bcl-2-family mRNAs or proteins are currently in clinical testing, raising hopes that a new class of anticancer drugs may soon be available.

The roles of microRNA in cancer and apoptosis

microRNAs (miRNAs) are highly conserved, non-protein-coding RNAs that function to regulate gene expression. In mammals this regulation is primarily carried out by repression of translation. miRNAs play important roles in homeostatic processes such as development, cell proliferation and cell death. Recently the dysregulation of miRNAs has been linked to cancer initiation and progression, indicating that miRNAs may play roles as tumour suppressor genes or oncogenes. The role of miRNAs in apoptosis is not fully understood, however, evidence is mounting that miRNAs are important in this process. The dysregulation of miRNAs involved in apoptosis may provide a mechanism for cancer development and resistance to cancer therapy. This review examines the biosynthesis of miRNA, the mechanisms of miRNA target regulation and the involvement of miRNAs in the initiation and progression of human cancer. It will include miRNAs involved in apoptosis, specifically those miRNAs involved in the regulation of apoptotic pathways and tumour suppressor/oncogene networks. It will also consider emerging evidence supporting a role for miRNAs in modulating sensitivity to anti-cancer therapy.

Regulatory T cells as central regulators of both autoimmunity and B cell malignancy in New Zealand Black mice

Regulatory T cells (Tregs) play an important role in protection against autoimmune disease and are also known to be potent inhibitors of anti-tumor immune responses. The New Zealand Black (NZB) mouse is a murine model for both autoimmune diseases, since high levels of autoantibodies are present, and human CLL, due to the expansion of malignant B-1 cells. In this study, we examined the functional role of CD4(+)CD25(+) Foxp3(+) Tregs in these different manifestations. Flow cytometric analysis showed increased levels of Tregs in NZB mice compared to healthy C57Bl/6 controls. Aged NZB mice that have developed a B-1 cell malignancy identified as IgM(+)CD5(+), have the most pronounced increase in Tregs. Ex vivo treatment of splenocytes from NZB mice with IFN-alpha resulted in a decrease in the frequency of Tregs and malignant B-1 cells. In vivo treatment of both NZB and C57Bl/6 mice with poly (I:C), a potent inducer of IFN-alpha, also led to a decrease in the levels of Tregs and malignant B-1 cells (NZB only) while amplifying autoimmune manifestations. These results indicate that while high levels of Tregs found in NZB mice might suppress a more severe autoimmune disease, they may also contribute to the development of the B cell malignancy.

MicroRNA profiling as a tool to understand prognosis, therapy response and resistance in breast cancer

Despite advances in detection and therapies, breast cancer is still the leading cause of cancer death in women worldwide. The etiology of this neoplasm is complex, and both genetic and environmental factors contribute to the complicated scenario. Gene profiling studies have been extensively used over the past decades as a powerful tool in defining the signature of different cancers and in predicting outcome and response to therapies. More recently, a new class of small non-coding RNAs, microRNAs (miRNAs), able to regulate gene expression binding seed sequences on the 3'UTR of mRNA targets, has been linked to several human diseases, including cancer. An increasing amount of experimental evidence shows that miRNAs are aberrantly expressed in different tumour types, and that they can have a causal role in tumourigenesis. Here, we describe and discuss the evidence supporting the association between miRNAs and breast cancer, underlining their role in the development of this neoplasia, and the impact on putative innovative therapeutical approaches.

MicroRNAs: key players in the immune system, differentiation, tumorigenesis and cell death

Micro (mi)RNAs are small, highly conserved noncoding RNAs that control gene expression post-transcriptionally either via the degradation of target mRNAs or the inhibition of protein translation. Each miRNA is believed to regulate the expression of multiple mRNA targets, and many miRNAs have been linked to the initiation and progression of human cancer. miRNAs control various activities of the immune system and different stages of hematopoietic development, and their misexpression is the cause of various blood malignancies. Certain miRNAs have oncogenic activities, whereas others have the potential to act as tumor suppressors. Because they control fundamental processes such as differentiation, cell growth and cell death, the study of the role of miRNAs in human neoplasms holds great promise for novel forms of therapy. Here, we summarize the role of miRNAs and their targets in contributing to human cancers and their function as regulators of apoptotic pathways and the immune system.