Association of a microRNA/TP53 feedback circuitry with pathogenesis and outcome of B-cell chronic lymphocytic leukemia

The long noncoding RNA sONE represses triple-negative breast cancer aggressiveness through inducing the expression of miR-34a, miR-15a, miR-16, and let-7a

Triple-negative breast cancer (TNBC) represents an aggressive breast cancer subtype. Among young females, TNBC is the leading cause of cancer-related mortalities. Recently, long noncoding RNAs (lncRNAs) are representing a promising pool of regulators for tuning the aggressiveness of several solid malignancies. However, this still needs further investigations in TNBC. The main aim of this study is to unravel the expression pattern of sONE lncRNA and its mechanistic role in TNBC. Results showed that sONE is restrictedly expressed in TNBC patients; its expression level is inversely correlated with the aggressiveness of the disease. sONE acts as a posttranscriptional regulator to endothelial nitric oxide synthase (eNOS) and thus affecting eNOS-induced nitric oxide (NO) production from TNBC cells measured by Greiss reagent. Mechanistically, sONE is a potential tumor suppressor lncRNA in TNBC cells; repressing cellular viability, proliferation, colony-forming ability, migration, and invasion capacities of MDA-MB-231. Furthermore, sONE effects were found to be extended to affect the maestro tumor suppressor TP53 and the oncogenic transcription factor c-Myc. Knocking down of sONE resulted in a marked decrease in TP53 and increase in c-Myc and consequently altering the expression status of their downstream tumor suppressor microRNAs (miRNAs) such as miR-34a, miR-15, miR-16, and let-7a. In conclusion, this study highlights sONE as a downregulated tumor suppressor lncRNA in TNBC cells acting through repressing eNOS-induced NO production, affecting TP53 and c-Myc proteins levels and finally altering the levels of a panel of tumor suppressor miRNAs downstream TP53/c-Myc proteins.

MicroRNA in Brain pathology: Neurodegeneration the Other Side of the Brain Cancer

The mammalian brain is made up of billions of neurons and supporting cells (glial cells), intricately connected. Molecular perturbations often lead to neurodegeneration by progressive loss of structure and malfunction of neurons, including their death. On the other side, a combination of genetic and cellular factors in glial cells, and less frequently in neurons, drive oncogenic transformation. In both situations, microenvironmental niches influence the progression of diseases and therapeutic responses. Dynamic changes that occur in cellular transcriptomes during the progression of developmental lineages and pathogenesis are controlled through a variety of regulatory networks. These include epigenetic modifications, signaling pathways, and transcriptional and post-transcriptional mechanisms. One prominent component of the latter is small non-coding RNAs, including microRNAs, that control the vast majority of these networks including genes regulating neural stemness, differentiation, apoptosis, projection fates, migration and many others. These cellular processes are also profoundly dependent on the microenvironment, stemness niche, hypoxic microenvironment, and interactions with associated cells including endothelial and immune cells. Significantly, the brain of all other mammalian organs expresses the highest number of microRNAs, with an additional gain in expression in the early stage of neurodegeneration and loss in expression in oncogenesis. However, a mechanistic explanation of the concept of an apparent inverse correlation between the odds of cancer and neurodegenerative diseases is only weakly developed. In this review, we thus will discuss widespread de-regulation of microRNAome observed in these two major groups of brain pathologies. The deciphering of these intricacies is of importance, as therapeutic restoration of pre-pathological microRNA landscape in neurodegeneration must not lead to oncogenesis and vice versa. We thus focus on microRNAs engaged in cellular processes that are inversely regulated in these diseases. We also aim to define the difference in microRNA networks between pro-survival and pro-apoptotic signaling in the brain.

miR-34a: a new player in the regulation of T cell function by modulation of NF-κB signaling

NF-κB functions as modulator of T cell receptor-mediated signaling and transcriptional regulator of miR-34a. Our in silico analysis revealed that miR-34a impacts the NF-κB signalosome with miR-34a binding sites in 14 key members of the NF-κB signaling pathway. Functional analysis identified five target genes of miR-34a including PLCG1, CD3E, PIK3CB, TAB2, and NFΚBIA. Overexpression of miR-34a in CD4⁺ and CD8⁺ T cells led to a significant decrease of NFΚBIA as the most downstream cytoplasmic NF-κB member, a reduced cell surface abundance of TCRA and CD3E, and to a reduction of T cell killing capacity. Inhibition of miR-34a caused an increase of NFΚBIA, TCRA, and CD3E. Notably, activation of CD4⁺ and CD8⁺ T cells entrails a gradual increase of miR-34a. Our results lend further support to a model with miR-34a as a central NF-κB regulator in T cells.

Increased serum levels of Galectin-9 in patients with chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is the most common type of leukemia in adults. Despite improvements in treatment, CLL is still considered an incurable disease. The aim of the present study was to evaluate galectin-1, -3 and -9 (Gal-1, -3 and -9) and Gal-3 binding protein (Gal-3BP) as prognostic and predictive factors in patients with CLL. Serum concentrations of Gal-1, -3 and -9 and Gal-3BP were measured in 48 patients with CLL and 30 control patients, using multiplex bead arrays. In patients with CLL, galectin concentrations were assessed prior to, during and following treatment. In patients with CLL who were untreated, galectin concentrations were measured twice with a 6-month interval. The serum level of Gal-9 was significantly increased (P<0.0001) in patients with CLL compared with the control group, and was associated with the clinical stage according to Binet classification, as well as poor cytogenetic and serum CLL prognostic factors. In addition, patients with CLL, who exhibited treatment failure, exhibited higher concentrations of Gal-9 (P=0.06) and Gal-3BP (P=0.009) at the end of the treatment when compared with patients under complete remission or stabilization of the disease. The serum level of Gal-3 was significantly decreased (P=0.012) in patients with CLL compared with the control group. These results suggest that Gal-9 is a potential prognostic factor in patients with CLL. The predictive value of Gal-9 requires further study in larger cohorts of patients.

In vitro analysis of microRNA-26a in chronic lymphocytic leukemia cells

microRNA (miRNA)‑26a‑loaded liposomes were prepared in the present study for effective treatment of leukemia. The results demonstrated that miRNA‑26a reduced the viability of chronic lymphocytic leukemia (CLL) cells in a concentration‑dependent manner. Cells treated with miRNA‑26a‑loaded liposomes exhibited increased rates of apoptosis, as determined by flow cytometry and Hoechst 33342 staining. Western blot analysis revealed an increased apoptotic effect of miRNA‑26a‑loaded liposomes compared with control. Treatment with these liposomes resulted in significant downregulation of the expression of the miRNA‑26a target genes, myeloid cell leukemia 1 and cyclin‑dependent kinase 6. Taken together, the results of the present study indicate that miRNA‑26a exerts apoptosis‑inducing and anticancer effects on leukemia cells, suggesting therapeutic potential. This approach may be possible to extrapolate to other neoplasms, including lymphomas and acute myeloid leukemia.

MicroRNAs as Biomarkers of B-cell Lymphoma

B-cell lymphomas represent a diverse group of neoplasms classified primarily by histopatholgy and are often challenging to accurately diagnose. Despite having been recognized less than 20 years ago, microRNAs (miRNAs) have emerged as one of the most promising class of cancer molecular biomarkers and are particularly attractive as they can be readily detected in formalin-fixed paraffin-embedded biopsy material and biological fluids such as blood. Many of the identified B-cell lymphoma miRNA biomarkers also play crucial regulatory roles in normal B-cell development. Below we consider the identity, function, and biomarker potential of miRNAs in B-cell lymphoma and most importantly the barriers that remain to be overcome if they are really to become part of routine clinical practice.

MicroRNAs in Autoimmunity and Hematological Malignancies

Autoimmunity and hematological malignancies are often concomitant in patients. A causal bidirectional relationship exists between them. Loss of immunological tolerance with inappropriate activation of the immune system, likely due to environmental and genetic factors, can represent a breeding ground for the appearance of cancer cells and, on the other hand, blood cancers are characterized by imbalanced immune cell subsets that could support the development of the autoimmune clone. Considerable effort has been made for understanding the proteins that have a relevant role in both processes; however, literature advances demonstrate that microRNAs (miRNAs) surface as the epigenetic regulators of those proteins and control networks linked to both autoimmunity and hematological malignancies. Here we review the most up-to-date findings regarding the miRNA-based molecular mechanisms that underpin autoimmunity and hematological malignancies.

Exosome-carried microRNA-based signature as a cellular trigger for the evolution of chronic lymphocytic leukemia into Richter syndrome

Even if considered a cumulative and not a proliferative CD5+ B-cell neoplasm, chronic lymphocytic leukemia (CLL) has a proliferation rate higher than that recognized earlier, especially in the lymphoid tissues. Some patients with CLL develop a clinical syndrome entitled Richter syndrome (RS). Understanding CLL genetics and epigenetics may help to elucidate the molecular basics of the clinical heterogeneity of this type of malignancy. In the present project we aimed to identify a microRNA species that can predict the evolution of therapy-resistant CLL towards RS. In the first phase of our study, microRNA-19b was identified as a possible target, and in the second phase, we transfected three different CLL cell lines with microRNA-19b mimic and inhibitor and assessed the potential role on leukemia cells in vitro. The mechanism by which miR-19b acts were identified as the upregulation of Ki67 and downregulation of p53. This was further supported through RT-PCR and western blotting on CLL cell lines, as well as by next generation sequencing on two patients diagnosed with CLL that evolved into RS.

Friend or Foe: MicroRNAs in the p53 network

The critical tumor suppressor gene TP53 is either lost or mutated in more than half of human cancers. As an important transcriptional regulator, p53 modulates the expression of many microRNAs. While wild-type p53 uses microRNAs to suppress cancer development, microRNAs that are activated by gain-of-function mutant p53 confer oncogenic properties. On the other hand, the expression of p53 is tightly controlled by a fine-tune machinery including microRNAs. MicroRNAs can target the TP53 gene directly or other factors in the p53 network so that expression and function of either the wild-type or the mutant forms of p53 is downregulated. Therefore, depending on the wild-type or mutant p53 context, microRNAs contribute substantially to suppress or exacerbate tumor development.

Exosomal miRNAs as novel cancer biomarkers: Challenges and opportunities

A biomarker with high specificity and sensitivity, is a basic requirement for non-invasive cancer diagnosis. Exosomes are a type of lipid bilayer extracellular vesicles (EVs), containing different components, including proteins, lipids, DNA, messenger RNA (mRNA), and non-coding RNAs. Increasing evidence indicates that nucleic acids are protected by exosome lipid membrane. These vesicles are almost released from all cell types, into biological fluids. In cancer, the expression of microRNAs (miRNAs), located in the tumor cell-derived exosomes, is deregulated and it could be led to metastasis and therapy resistance. Due to the presence of exosomes in various body fluids and the stability of miRNAs in exosomes, exosomal miRNAs can provide a new class of biomarkers for early and minimally invasive cancer diagnosis. In this article, we review the miRNAs and their roles in cancer. Furthermore, we explain the different types of EVs, especially exosomes, and their functional roles in cancer. At the end, we discuss about the importance of exosomal miRNAs for cancer diagnosis. As well as, we briefly summarize the exosome isolation techniques and obstacles, limiting the clinical applications of exosomal miRNAs.

BRD7 expression and c-Myc activation forms a double-negative feedback loop that controls the cell proliferation and tumor growth of nasopharyngeal carcinoma by targeting oncogenic miR-141

Background

miR-141 is up-regulated and plays crucial roles in nasopharyngeal carcinoma (NPC). However, the molecular mechanism underlying the dysregulation of miR-141 is still obscure.

Methods

Thus, the ChIP-PCR was performed to identify the c-Myc-binding sites in miR-141 and BRD7. qRT-PCR, western blot and immunohistochemistry assays were used to detect the expression of miR-141 and its up/down stream molecules. The rescue experiments on the c-Myc/miR-141 axis were performed in vitro and in vivo.

Results

Our results showed that the levels of mature miR-141, pre-miR-141 and pri-miR-141 were downregulated in c-Myc knockdown NPC cells. Meanwhile, c-Myc transactivates the expression of miR-141 by binding its promoter region. Moreover, BRD7 was identified as a co-factor of c-Myc to negatively regulate the activation of c-Myc/miR-141 axis, as well as a direct target of c-Myc. Moreover, restoration of miR-141 in c-Myc knockdown NPC cells notably rescued the effect of c-Myc on cell proliferation and tumor growth, as well as the blocking of PTEN/AKT pathway. Additionally, the expression of c-Myc was positively correlated with that of miR-141 and the clinical stages of NPC patients and negatively associated with the expression of BRD7. Our findings demonstrated that BRD7 expression and c-Myc activation forms a negative feedback loop to control the cell proliferation and tumor growth by targeting miR-141.

Conclusions

These observations provide new mechanistic insights into the dysregulation of miR-141 expression and a promising therapeutic option for NPC.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0734-2) contains supplementary material, which is available to authorized users.

miR-195 targets cyclin D3 and survivin to modulate the tumorigenesis of non-small cell lung cancer

miR-195 has recently been reported to function as a tumor suppressor in various cancers, including non-small cell lung cancer (NSCLC). However, the mechanisms by which miR-195 represses the tumorigenesis of NSCLC cells are not fully understood. We performed a high-throughput screen using an miRNA mimic library and confirmed the identification of miR-195 as a tumor suppressor in NSCLC. We demonstrated that overexpression or induced expression of miR-195 in lung tumors slows tumor growth and that repression of miR-195 accelerates tumor growth. In addition, we found that knockout of miR-195 promotes cancer cell growth. We demonstrated that miR-195 targets cyclin D3 to cause cell cycle arrest at the G1 phase and that miR-195 targets survivin to induce apoptosis and senescence in NSCLC cells. Overexpression of cyclin D3 or survivin reverses the effects of miR-195 in NSCLC cells. Through the analysis of data from The Cancer Genome Atlas, we confirmed that the expression of miR-195 is lower in tumors than in adjacent normal tissues and that low expression of miR-195 is associated with poor survival in both lung adenocarcinoma and squamous cell carcinoma patients. Specifically, we found that BIRC5, which codes for survivin, is upregulated in both adenocarcinoma and squamous cell carcinoma tissues and that high expression of BIRC5 is associated with poor survival in adenocarcinoma, but not squamous cell carcinoma. In addition, the ratio of miR-195 level to BIRC5 level is associated with both recurrence-free and overall survival in lung adenocarcinoma. Our results suggest that the miR-195/BIRC5 axis is a potential target for treatment of lung adenocarcinoma specifically, and NSCLC in general.

BCL2 and miR-15/16: from gene discovery to treatment

In 1984, we investigated the t(14;18) chromosomal translocations that frequently occur in patients with follicular lymphoma. We first identified a locus on chromosome 18 involved in these translocations with the chromosome 14 containing the immunoglobulin heavy chain locus. Within this region on chromosome 18, we then discovered a gene that we called BCL2, which was activated by the translocations. Since that time, many studies determined that BCL2 is one of the most important oncogenes involved in cancer by inhibiting apoptosis. In 2002, we studied 13q deletions in chronic lymphocytic leukemia (CLL) and found that the microRNA cluster miR-15a/miR-16-1 (miR-15/16) is deleted by 13q deletions. In 2005, we discovered that miR-15/16 function as tumor suppressors by directly targeting BCL2. Thus the loss of two negative regulators of BCL2 expression results in overexpression of BCL2. Very recently, a specific BCL2 inhibitor ABT-199 (Venetoclax) was developed and approved by FDA for CLL treatment. Thus it took 32 years from fundamental discovery of a critical oncogene to the development of a drug capable to cure CLL. In this review, we discuss the discovery, functions and clinical relevance of miR-15/16 and BCL2.

MicroRNAs Role in Prostate Cancer

Prostate cancer still represents a major health problem for men worldwide. Due to the specific limitation of the currently used clinical biomarkers for prostate cancer, there is a need to identify new and more accurate prostate-specific biomarkers, both for diagnosis and prediction. Small noncoding species of RNAs called microRNAs (miRNAs) have emerged as possible biomarkers in cancer tissues as well as biological fluids, including for prostate cancer. Moreover, it has been shown that miRNAs could be used as therapeutic targets in different cancer types, including prostate cancer, playing an important role in improving diagnosis and prognosis; and miRNAs have the potential to be clinically useful as predictors of response to personalized cancer therapy and as predictors of prognosis. The analysis of miRNAs in prostate tissue is rather straightforward and has been routinely done on fresh tissue. In addition, due to the more stable nature of miRNAs, they are amenable to be analyzed in archived formalin fixed paraffin embedded tissue as well, and also in serum, plasma and urine, using various analytical platforms including microarrays, next generation sequencing and real time PCR. Moreover, although the existence or prostasomes (microvesicles secreted by prostate cells including prostate cancer cells) has been known for years and they were studied as a source of biomarkers for prostate cancer, only recently it has been described that these vesicles also contain miRNAs that could be used as biomarkers in prostate cancer. This chapter underscores the feasibility of current technologies for miRNA analysis and their importance in prostate cancer biology. Moreover, elucidating the specific alteration of miRNA expression and how to modulate it in prostate tissue will open new avenues for developing therapeutic strategies for prostate cancer treatment.

Apoptosis signaling and BCL-2 pathways provide opportunities for novel targeted therapeutic strategies in hematologic malignances

Apoptosis is an essential biological process involved in tissue homeostasis and immunity. Aberrations of the two main apoptotic pathways, extrinsic and intrinsic, have been identified in hematological malignancies; many of these aberrations are associated with pathogenesis, prognosis and resistance to standard chemotherapeutic agents. Targeting components of the apoptotic pathways, especially the chief regulatory BCL-2 family in the intrinsic pathway, has proved to be a promising therapeutic approach for patients with hematological malignances, with the expectation of enhanced efficacy and reduced adverse events. Continuous investigations regarding the biological importance of each of the BCL-2 family components and the clinical rationale to achieve optimal therapeutic outcomes, using either monotherapy or in combination with other targeted agents, have generated inspiring progress in the field. Genomic, epigenomic and biological analyses including BH3 profiling facilitate effective evaluation of treatment response, cancer recurrence and drug resistance. In this review, we summarize the biological features of each of the components in the BCL-2 apoptotic pathways, analyze the regulatory mechanisms and the pivotal roles of BCL-2 family members in the pathogenesis of major types of hematologic malignances, and evaluate the potential of apoptosis- and BCL-2-targeted strategies as effective approaches in anti-cancer therapies.

CUL2 overexpression driven by CUL2/E2F1/miR-424 regulatory loop promotes HPV16 E7 induced cervical carcinogenesis

It has been shown that HPV16 E7, but not other genotypes, can bind to scaffold protein CUL2 during inducing cervical carcinogenesis, but the expression level, associated regulating mechanism, and potential carcinogenicity of CUL2 itself is still unknown as yet. Here, we demonstrated that CUL2 was specifically overexpressed in HPV16 positive cervical cancer cells and tissues, and CUL2 expression was significantly increased along with the cervical lesion progression and positively correlated with HPV16 E7. CUL2 knockdown slowed the growth of xenograft tumors in mouse models. Importantly, CUL2 specifically bound to HPV16 E7, but not HPV18 E7. Moreover, CUL2 acted as a direct target of miR-424, and reversely suppressed miR-424; E2F transcription factor 1 (E2F1) suppressed miR-424 expression; CUL2 bound to E2F1 and promoted E2F1 expression. Our results indicate the existence of a regulatory loop among CUL2, E2F1, and miR-424 in HPV16 positive cervical cancer cells. Our results suggest that E7 recruited CUL2, driven by CUL2/E2F1/miR-424 regulatory loop, is overexpressed and accelerates HPV16-induced cervical carcinogenesis. Our findings may serve as one of the explanations for a clinical phenomenon that HPV16 possesses the strongest cervical carcinogenicity among high-risk HPV genotypes.

MicroRNA dysregulation to identify therapeutic target combinations for chronic lymphocytic leukemia

Loss of miR-15/16 is the most common genetic lesion in chronic lymphocytic leukemia (CLL), promoting overexpression of BCL2, which factors in leukemia pathogenesis. Indeed, an inhibitor of Bcl2, venetoclcax, is highly active in the treatment of patients with CLL. However, single-agent venetoclcax fails to eradicate minimal residual disease in most patients. Accordingly, we were interested in other genes that may be regulated by miR-15/16, which may target other drivers in CLL. We found that miR-15/16 targets ROR1, which encodes an onco-embryonic surface protein expressed on the CLL cells of over 90% of patients, but not on virtually all normal postpartum tissues. CLL with high-level expression of ROR1 also have high-level expression of Bcl2, but low-to-negligible miR-15/16 Moreover, CLL cases with high-level ROR1 have deletion(s) at the chromosomal location of the genes encoding miR-15/16 (13q14) more frequently than cases with low-to-negligible ROR1, implying that deletion of miR-15/16 may promote overexpression of ROR1, in addition to BCL2 ROR1 is a receptor for Wnt5a, which can promote leukemia-cell proliferation and survival, and can be targeted by cirmtuzumab, a humanized anti-ROR1 mAb. We find that this mAb can enhance the in vitro cytotoxic activity of venetoclcax for CLL cells with high-level expression of ROR1, indicating that combining these agents, which target ROR1 and Bcl2, may have additive, if not synergistic, activity in patients with this disease.

MicroRNA16 regulates glioma cell proliferation, apoptosis and invasion by targeting Wip1-ATM-p53 feedback loop

The present study aimed to investigate the role and underlying mechanisms of microRNA16 (miR-16) on proliferation, apoptosis and invasion of glioma cells. The cell models of miR-16 upregulation and Negative control group (NC group) were built. The cell functions of different groups were detected by colony formation assay, transwell chamber assay, proliferation, apoptosis and cycle experiments. The intracranial orthotopic transplantation animal models were built to different groups: miR-16 agomir group, miR-16 antagomir group and their NC group. The expressions of miR-16, Wip1, ATM and p53 were measured by qRT-PCR, western blot and immunohistochemistry. As a result, miR-16 overexpressed groups had lower cloning formation rate and proliferation rate, less invasive cells, higher early apoptosis rate than the control groups. G1 phase was significantly smaller compared miR-16 overexpressed groups with the control groups, and S phase significantly lesser. Cell growth was retardated. Differences were statistically significant (P <0.05). Compared with miR-16 overexpressed groups and NC groups, the Wip1 gene and protein expression were downregulated, while ATM and p53 genes, p-ATM and p-p53 proteins were upregulated. The differences were statistically significant (P <0.05). Taken together, our findings demonstrated that miR-16 suppressed glioma cell proliferation and invasion, promoted apoptosis and inhibited cell cycle by targeting Wip1-ATM-p53 signaling pathway.

Role of the tRNA-Derived Small RNAs in Cancer: New Potential Biomarkers and Target for Therapy

Noncoding RNAs are untranslated RNA molecules that can be divided into two main types: infrastructural, including transfer RNAs (tRNAs) and ribosomal RNAs (rRNAs), and regulatory, including long ncRNAs (lncRNAs) and small ncRNAs (sRNA). Among small ncRNA, the role of microRNAs (miRNAs) and Piwi-interacting RNAs (piRNAs) in cancer is well documented. Recently, other small ncRNAs have been described. In particular, tRNA-derived small RNAs (tsRNA) have been found to be frequently dysregulated in cancer. Since tsRNAs can be considered unique sequences and are able to bind both Argonaute proteins (like miRNAs) and Piwi proteins (like piRNAs), their dysregulation could play a critical role in cancer by interfering with gene expression regulation at different levels. Like microRNAs, ts-53 (previously known as miR-3676) interacts with the 3'UTR of TCL1, therefore supporting a role for tsRNAs on the posttranscriptional regulation of gene expression. Like piRNAs, tsRNAs are produced as single-stranded molecules and can interact with DNA and histone methylation machinery, suggesting a role in the pretranscriptional regulation of gene expression. Herein, we describe the most recent findings about the role of tsRNAs in cancer.

Animal Models to Study MicroRNA Function

The discovery of the microRNAs, lin-4 and let-7 as critical mediators of normal development in Caenorhabditis elegans and their conservation throughout evolution has spearheaded research toward identifying novel roles of microRNAs in other cellular processes. To accurately elucidate these fundamental functions, especially in the context of an intact organism, various microRNA transgenic models have been generated and evaluated. Transgenic C. elegans (worms), Drosophila melanogaster (flies), Danio rerio (zebrafish), and Mus musculus (mouse) have contributed immensely toward uncovering the roles of multiple microRNAs in cellular processes such as proliferation, differentiation, and apoptosis, pathways that are severely altered in human diseases such as cancer. The simple model organisms, C. elegans, D. melanogaster, and D. rerio, do not develop cancers but have proved to be convenient systesm in microRNA research, especially in characterizing the microRNA biogenesis machinery which is often dysregulated during human tumorigenesis. The microRNA-dependent events delineated via these simple in vivo systems have been further verified in vitro, and in more complex models of cancers, such as M. musculus. The focus of this review is to provide an overview of the important contributions made in the microRNA field using model organisms. The simple model systems provided the basis for the importance of microRNAs in normal cellular physiology, while the more complex animal systems provided evidence for the role of microRNAs dysregulation in cancers. Highlights include an overview of the various strategies used to generate transgenic organisms and a review of the use of transgenic mice for evaluating preclinical efficacy of microRNA-based cancer therapeutics.

Anti-leukemic activity of microRNA-26a in a chronic lymphocytic leukemia mouse model

Dysregulation of microRNAs (miRNAs) plays an important role in the pathogenesis of chronic lymphocytic leukemia (CLL). The Eμ-TCL1 transgenic mouse develops a form of leukemia that is similar to the aggressive type of human B-CLL, and this valuable model has been widely used for testing novel therapeutic approaches. Here, we adopted this model to investigate the potential effects of miR-26a, miR-130an and antimiR-155 in CLL therapy. Improved delivery of miRNA molecules into CLL cells was obtained by developing a novel system based on lipid nanoparticles conjugated with an anti-CD38 monoclonal antibody. This methodology has proven to be highly effective in delivering miRNA molecules into leukemic cells. Short- and long-term experiments showed that miR-26a, miR-130a and anti-miR-155 increased apoptosis after in vitro and in vivo treatment. Of this miRNA panel, miR-26a was the most effective in reducing leukemic cell expansion. Following long-term treatment, apoptosis was readily detectable by analyzing cleavage of PARP and caspase-7. These effects could be directly attributed to miR-26a, as confirmed by significant downregulation of its proven targets, namely cyclin-dependent kinase 6 and Mcl1. The results of this study are relevant to two distinct areas. The first is related to the design of a technical strategy and to the selection of CD38 as a molecular target on CLL cells, both consenting efficient and specific intracellular transfer of miRNA. The original scientific finding inferred from the above approach is that miR-26a can elicit in vivo anti-leukemic activities mediated by increased apoptosis.

tsRNA signatures in cancer

Small, noncoding RNAs are short untranslated RNA molecules, some of which have been associated with cancer development. Recently we showed that a class of small RNAs generated during the maturation process of tRNAs (tRNA-derived small RNAs, hereafter "tsRNAs") is dysregulated in cancer. Specifically, we uncovered tsRNA signatures in chronic lymphocytic leukemia and lung cancer and demonstrated that the ts-4521/3676 cluster (now called "ts-101" and "ts-53," respectively), ts-46, and ts-47 are down-regulated in these malignancies. Furthermore, we showed that tsRNAs are similar to Piwi-interacting RNAs (piRNAs) and demonstrated that ts-101 and ts-53 can associate with PiwiL2, a protein involved in the silencing of transposons. In this study, we extended our investigation on tsRNA signatures to samples collected from patients with colon, breast, or ovarian cancer and cell lines harboring specific oncogenic mutations and representing different stages of cancer progression. We detected tsRNA signatures in all patient samples and determined that tsRNA expression is altered upon oncogene activation and during cancer staging. In addition, we generated a knocked-out cell model for ts-101 and ts-46 in HEK-293 cells and found significant differences in gene-expression patterns, with activation of genes involved in cell survival and down-regulation of genes involved in apoptosis and chromatin structure. Finally, we overexpressed ts-46 and ts-47 in two lung cancer cell lines and performed a clonogenic assay to examine their role in cell proliferation. We observed a strong inhibition of colony formation in cells overexpressing these tsRNAs compared with untreated cells, confirming that tsRNAs affect cell growth and survival.

MicroRNAs as Key Effectors in the p53 Network

The guardian of the genome p53 is embedded in a fine-spun network of MicroRNAs. p53 is able to activate or repress directly the transcription of MicroRNAs that are participating in the tumor-suppressive mission of p53. On the other hand, the expression of p53 is under tight control of MicroRNAs that are either targeting directly p53 or factors that are modifying its protein level or activity. Although the most important function of p53 is suggested to be transcriptional regulation, there are several nontranscriptional functions described. One of those regards the modulation of MicroRNA biogenesis. Wild-type p53 is increasing the maturation of selected MicroRNAs from the primary transcript to the precursor MiRNA by interacting with the Microprocessor complex. Furthermore, p53 is modulating the mRNA accessibility for certain MicroRNAs by association with the RISC complex and transcriptional regulation of RNA-binding proteins. In this way p53 is able to remodel the MiRNA-mRNA interaction network. As wild-type p53 is employing MicroRNAs to suppress cancer development, gain-of-function mutant p53 proteins use MicroRNAs to confer oncogenic properties like chemoresistance and the ability to drive metastasis. Like its wild-type counterpart mutant p53 is able to regulate MicroRNAs transcriptionally and posttranscriptionally. Mutant p53 affects the MiRNA processing at two cleavage steps through interfering with the Microprocessor complex and by downregulating Dicer and KSRP, a modulator of MiRNA biogenesis. Thus, MicroRNAs are essential components in the p53 pathway, contributing substantially to combat or enhance tumor development depending on the wild-type or mutant p53 context.

Down-regulation of miR-15a/b accelerates fibrotic remodelling in the Type 2 diabetic human and mouse heart

Aim: Myocardial fibrosis is a well-established cause of increased myocardial stiffness and subsequent diastolic dysfunction in the diabetic heart. The molecular regulators that drive the process of fibrotic events in the diabetic heart are still unknown. We determined the role of the microRNA (miR)-15 family in fibrotic remodelling of the diabetic heart.Methods and results: Right atrial appendage (RAA) and left ventricular (LV) biopsy tissues collected from diabetic and non-diabetic (ND) patients undergoing coronary artery bypass graft surgery showed significant down-regulation of miR-15a and -15b. This was associated with marked up-regulation of pro-fibrotic transforming growth factor-β receptor-1 (TGFβR1) and connective tissue growth factor (CTGF), direct targets for miR-15a/b and pro-senescence p53 protein. Interestingly, down-regulation of miR-15a/b preceded the development of diastolic dysfunction and fibrosis in Type 2 diabetic mouse heart. Therapeutic restoration of miR-15a and -15b in HL-1 cardiomyocytes reduced the activation of pro-fibrotic TGFβR1 and CTGF, and the pro-senescence p53 protein expression, confirming a causal regulation of these fibrotic and senescence mediators by miR-15a/b. Moreover, conditioned medium (CM) collected from cardiomyocytes treated with miR-15a/b markedly diminished the differentiation of diabetic human cardiac fibroblasts.Conclusion: Our results provide first evidence that early down-regulation of miR-15a/b activates fibrotic signalling in diabetic heart, and hence could be a potential target for the treatment/prevention of diabetes-induced fibrotic remodelling of the heart.

Plasma Viral miRNAs Indicate a High Prevalence of Occult Viral Infections

Prevalence of Kaposi sarcoma-associated herpesvirus (KSHV/HHV-8) varies greatly in different populations. We hypothesized that the actual prevalence of KSHV/HHV8 infection in humans is underestimated by the currently available serological tests. We analyzed four independent patient cohorts with post-surgical or post-chemotherapy sepsis, chronic lymphocytic leukemia and post-surgical patients with abdominal surgical interventions. Levels of specific KSHV-encoded miRNAs were measured by reverse transcription-quantitative polymerase chain reaction (RT-qPCR), and KSHV/HHV-8 IgG were measured by immunoassay. We also measured specific miRNAs from Epstein Barr Virus (EBV), a virus closely related to KSHV/HHV-8, and determined the EBV serological status by ELISA for Epstein-Barr nuclear antigen 1 (EBNA-1) IgG. Finally, we identified the viral miRNAs by in situ hybridization (ISH) in bone marrow cells. In training/validation settings using independent multi-institutional cohorts of 300 plasma samples, we identified in 78.50% of the samples detectable expression of at least one of the three tested KSHV-miRNAs by RT-qPCR, while only 27.57% of samples were found to be seropositive for KSHV/HHV-8 IgG (P < 0.001). The prevalence of KSHV infection based on miRNAs qPCR is significantly higher than the prevalence determined by seropositivity, and this is more obvious for immuno-depressed patients. Plasma viral miRNAs quantification proved that EBV infection is ubiquitous. Measurement of viral miRNAs by qPCR has the potential to become the “gold” standard method to detect certain viral infections in clinical practice.

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There is no agreement on a standard assay to detect the true prevalence of Kaposi sarcoma-associated herpesvirus (KSHV) infection.

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Measurement of the viral miRNAs in plasma by RT-qPCR allows a direct and accurate assessment of viral infection.

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Measurement of the viral miRNAs in plasma by RT-qPCR shows prevalence of KSHV infection in immuno-depressed patients.

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Measurement of plasma viral miRNAs for viral infection assessment has the potential to become a “gold” standard method in the clinical practice.

Chronic viral infections represent risk factors for diseases and development of infection-related complications. There is no agreement on a standard assay to detect the true prevalence of Kaposi sarcoma-associated herpesvirus (KSHV) infection. The current method used in the clinical practice (ELISA-test) identifies a great geographic variation in KSHV seroprevalence and may underestimate the true-prevalence of KSHV infection. Here we showed that detection of plasma viral miRNAs levels for the identification of viral infection (e.g., KSHV, Epstein-Bar virus or EBV) is more accurate than the current method for detection of virus-derived antigen, especially in patients with low number of immune cells.

miR-125b and miR-532-3p predict the efficiency of rituximab-mediated lymphodepletion in chronic lymphocytic leukemia patients. A French Innovative Leukemia Organization study

The underlying in vivo mechanisms of rituximab action remain incompletely understood in chronic lymphocytic leukemia. Recent data suggest that circulating micro-ribonucleic acids correlate with chronic lymphocytic leukemia progression and response to rituximab. Our study aimed at identifying circulating micro-ribonucleic acids that predict response to rituximab monotherapy in chronic lymphocytic leukemia patients. Using a hierarchical clustering of micro-ribonucleic acid expression profiles discriminating 10 untreated patients with low or high lymphocyte counts, we found 26 micro-ribonucleic acids significantly deregulated. Using individual real-time reverse transcription polymerase chain reaction, the expression levels of micro-ribonucleic acids representative of these two clusters were further validated in a larger cohort (n=61). MiR-125b and miR-532-3p were inversely correlated with rituximab-induced lymphodepletion (P=0.020 and P=0.001, respectively) and with the CD20 expression on CD19⁺ cells (P=0.0007 and P<0.0001, respectively). In silico analyses of genes putatively targeted by both micro-ribonucleic acids revealed a central role of the interleukin-10 pathway and CD20 (MS4A1) family members. Interestingly, both micro-ribonucleic acids were negatively correlated with MS4A1 expression, while they were positively correlated with MS4A3 and MSA47 Our results identify novel circulating predictive biomarkers for rituximab-mediated lymphodepletion efficacy in chronic lymphocytic leukemia, and suggest a novel molecular mechanism responsible for the rituximab mode of action that bridges miR-125b and miR-532-3p and CD20 family members. (clinicaltrials.gov Identifier: 01370772).

Chronic lymphocytic leukaemia

Chronic lymphocytic leukaemia (CLL) is a malignancy of CD5+ B cells that is characterized by the accumulation of small, mature-appearing lymphocytes in the blood, marrow and lymphoid tissues. Signalling via surface immunoglobulin, which constitutes the major part of the B cell receptor, and several genetic alterations play a part in CLL pathogenesis, in addition to interactions between CLL cells and other cell types, such as stromal cells, T cells and nurse-like cells in the lymph nodes. The clinical progression of CLL is heterogeneous and ranges from patients who require treatment soon after diagnosis to others who do not require therapy for many years, if at all. Several factors, including the immunoglobulin heavy-chain variable region gene (IGHV) mutational status, genomic changes, patient age and the presence of comorbidities, should be considered when defining the optimal management strategies, which include chemotherapy, chemoimmunotherapy and/or drugs targeting B cell receptor signalling or inhibitors of apoptosis, such as BCL-2. Research on the biology of CLL has profoundly enhanced our ability to identify patients who are at higher risk for disease progression and our capacity to treat patients with drugs that selectively target distinctive phenotypic or physiological features of CLL. How these and other advances have shaped our current understanding and treatment of patients with CLL is the subject of this Primer.

Expression of circulating miRNAs associated with lymphocyte differentiation and activation in CLL-another piece in the puzzle

Expression of microRNAs is altered in cancer. Circulating miRNA level assessed in body fluids commonly reflects their expression in tumor cells. In leukemias, however, both leukemic and nonleukemic cells compose circulating miRNA expression profile of peripheral blood. The latter contribution to extracellular miRNA pool may result in specific microenvironmental signaling, which promotes proliferation and survival. In our study, we used qT-PCR to assay peripheral blood serum of 22 chronic lymphocytic leukemia (CLL) patients for the expression of 84 miRNAs associated with activation and differentiation of B and T lymphocytes. Results were analyzed regarding the most important prognostic factors. We have found that the general expression of examined miRNAs in CLL patients was lower as compared to healthy volunteers. Only miR-34a-5p, miR31-5p, miR-155-5p, miR-150-5p, miR-15a-3p, and miR-29a-3p were expressed on a higher level. Alterations of expression observed in CLL patients involved miRNAs associated both with B and T lymphocyte differentiation and activation. The most important discriminating factors for all functional miRNA groups were trisomy 12, CD38 expression, B2M level, WBC, and NOTCH1 gene mutation. Correlation of expression of miRNAs related to T lymphocytes with prognostic factors proves their supportive function in a leukemic microenvironment. Further studies utilizing a larger test group of patients may warrant the identification of circulating miRNAs that are key players in intercellular interactions and should be considered in the design of microenvironment-targeted therapies.

MicroRNA Dysregulation to Identify Novel Therapeutic Targets

This paper describes how we discovered the juxtaposition of the MYC gene to the human immunoglobulin loci and how that finding was extended to characterize molecularly the t(14;18) chromosome translocation of follicular lymphoma and to clone the BCL2 gene. BCL2 is also overexpressed in CLL, the most common human leukemia. We discovered that most of human CLLs have a deletion of two microRNAs residing in the same polycistronic RNA, miR-15a and miR-16-1, and that these two microRNAs are negative regulators of BCL2. Thus, loss of miR-15/16 leads to overexpression of BCL2 that can be targeted by the new drug, venetoclax, that was recently approved by the FDA for the treatment of aggressive CLLs.

MicroRNAs in Oncogenesis and Tumor Suppression

MicroRNAs (MiRNAs) have emerged in the last 15 years as central players in the biology of cancer. Increasing lines of evidence have supported their regulatory role in the expression of both oncogenes and tumor-suppressor genes, progressively clarifying which genes are modulated by specific MiRNAs dysregulated in cancer. Intriguingly, a "target-specific" understanding of MiRNA function in oncology has been replaced by a more "pathway-specific" vision of their involvement in cancer biology. This work provides a state-of-the-art knowledge of the role of MiRNAs in the most frequently altered signaling pathways in cancer cells and provides an updated overview on some of the most relevant findings trying to decode the complex molecular mechanisms of cancer.

Combining Anti-Mir-155 with Chemotherapy for the Treatment of Lung Cancers

Purpose: The oncogenic miR-155 is upregulated in many human cancers, and its expression is increased in more aggressive and therapy-resistant tumors, but the molecular mechanisms underlying miR-155-induced therapy resistance are not fully understood. The main objectives of this study were to determine the role of miR-155 in resistance to chemotherapy and to evaluate anti-miR-155 treatment to chemosensitize tumors.Experimental Design: We performed in vitro studies on cell lines to investigate the role of miR-155 in therapy resistance. To assess the effects of miR-155 inhibition on chemoresistance, we used an in vivo orthotopic lung cancer model of athymic nude mice, which we treated with anti-miR-155 alone or in combination with chemotherapy. To analyze the association of miR-155 expression and the combination of miR-155 and TP53 expression with cancer survival, we studied 956 patients with lung cancer, chronic lymphocytic leukemia, and acute lymphoblastic leukemia.Results: We demonstrate that miR-155 induces resistance to multiple chemotherapeutic agents in vitro, and that downregulation of miR-155 successfully resensitizes tumors to chemotherapy in vivo We show that anti-miR-155-DOPC can be considered non-toxic in vivo We further demonstrate that miR-155 and TP53 are linked in a negative feedback mechanism and that a combination of high expression of miR-155 and low expression of TP53 is significantly associated with shorter survival in lung cancer.Conclusions: Our findings support the existence of an miR-155/TP53 feedback loop, which is involved in resistance to chemotherapy and which can be specifically targeted to overcome drug resistance, an important cause of cancer-related death. Clin Cancer Res; 23(11); 2891-904. ©2016 AACR.

Histologic transformation of chronic lymphocytic leukemia/small lymphocytic lymphoma

Although generally considered a clinically indolent neoplasm, CLL/SLL may undergo transformation to a clinically aggressive lymphoma. The most common form of transformation, to DLBCL, is also known as Richter syndrome. Transformation determines the course of the disease and is associated with unfavorable patient outcome. Precise detection of transformation and identification of predictive biomarkers and specific molecular pathways implicated in the pathobiology of transformation in CLL/SLL will enable personalized therapeutic approach and provide potential avenues for improving the clinical outcome of patients. In this review, we present an overview of the pathologic features, risk factors, and pathogenic mechanisms of CLL/SLL transformation. Am. J. Hematol. 91:1036-1043, 2016. © 2016 Wiley Periodicals, Inc.

MicroRNA-506 is up-regulated in the development of pancreatic ductal adenocarcinoma and is associated with attenuated disease progression

BACKGROUND

MicroRNA-506 (miR-506) has been reported to function in several tumors as a tumor suppressor gene or oncogene. However, the expression and role of miR-506 in pancreatic ductal adenocarcinoma (PDAC) remains unclear. In this study, we aimed to evaluate the phenotype of miR-506 in PDAC.

METHODS

Using miRNA in situ hybridization, we examined the expression of miR-506 in 113 PDACs and 87 paired normal pancreatic tissues. We evaluated miR-506 expression in PDAC cells, normal pancreatic ducts, and acinus/islands, and we analyzed the associations between miR-506 expression and the clinicopathologic characteristics of PDAC patients.

RESULTS

miR-506 expression was higher in PDAC than in matched normal pancreatic ductal cells (P < 0.001). On the other hand, the combined group of well and moderately differentiated PDACs showed higher levels of miR-506 than the poorly differentiated ones (P = 0.023). Moreover, miR-506 expression was negatively associated with pathologic T category (P = 0.004) and lymph node metastasis (P = 0.033), suggesting that miR-506 might inhibit the progression of PDAC.

CONCLUSIONS

Our results suggest that miR-506 either plays a role as an oncogene in the tumorigenesis and a tumor suppressor in the progression or serves as a house-keeping, tumor-suppressing miRNA, whose expression can be activated by oncogenic signals in early development to hinder the progression of PDAC.

miR-34 miRNAs Regulate Cellular Senescence in Type II Alveolar Epithelial Cells of Patients with Idiopathic Pulmonary Fibrosis

Pathologic features of idiopathic pulmonary fibrosis (IPF) include genetic predisposition, activation of the unfolded protein response, telomere attrition, and cellular senescence. The mechanisms leading to alveolar epithelial cell (AEC) senescence are poorly understood. MicroRNAs (miRNAs) have been reported as regulators of cellular senescence. Senescence markers including p16, p21, p53, and senescence-associated β-galactosidase (SA-βgal) activity were measured in type II AECs from IPF lungs and unused donor lungs. miRNAs were quantified in type II AECs using gene expression arrays and quantitative RT-PCR. Molecular markers of senescence (p16, p21, and p53) were elevated in IPF type II AECs. SA-βgal activity was detected in a greater percentage in type II AECs isolated from IPF patients (23.1%) compared to patients with other interstitial lung diseases (1.2%) or normal controls (0.8%). The relative levels of senescence-associated miRNAs miR-34a, miR-34b, and miR-34c, but not miR-20a, miR-29c, or miR-let-7f were significantly higher in type II AECs from IPF patients. Overexpression of miR-34a, miR-34b, or miR-34c in lung epithelial cells was associated with higher SA-βgal activity (27.8%, 35.1%, and 38.2%, respectively) relative to control treated cells (8.8%). Targets of miR-34 miRNAs, including E2F1, c-Myc, and cyclin E2, were lower in IPF type II AECs. These results show that markers of senescence are uniquely elevated in IPF type II AECs and suggest that the miR-34 family of miRNAs regulate senescence in IPF type II AECs.

Ibrutinib downregulates a subset of miRNA leading to upregulation of tumor suppressors and inhibition of cell proliferation in chronic lymphocytic leukemia

The lymph node (LN) is the site of chronic lymphocytic leukemia (CLL) cell activation and proliferation. Aberrant microRNA (miRNA) expression has been shown to have a role in CLL pathogenesis; however, a comparison of miRNA expression between CLL cells in the LN and the peripheral blood (PB) has previously not been reported. On the basis of the analysis of 17 paired LN and PB samples from CLL patients, we identify a panel of miRNAs that are increased in LN CLL cells correlating with an activation phenotype. When evaluated in CLL cells from 38 patients pre and post treatment with ibrutinib, a subset of these miRNAs (miR-22, miR-34a, miR-146b and miR-181b) was significantly decreased in response to ibrutinib. A concomitant increase in putative miRNA target transcripts (ARID1B, ARID2, ATM, CYLD, FOXP1, HDAC1, IBTK, PTEN and SMAD4) was also observed. Functional studies confirmed targets of ibrutinib-responsive miRNAs to include messenger RNA transcripts of multiple tumor suppressors. Knockdown of endogenous miR-34a and miR146b resulted in increased transcription of tumor suppressors and inhibition of cell proliferation. These findings demonstrate that ibrutinib downregulates the expression of a subset of miRNAs related to B-cell activation leading to increased expression of miRNA targets including tumor suppressors and a reduction in cell proliferation.

miRNA-15a/16: as tumor suppressors and more

Since their first discovery in chronic lymphocytic leukemia, miR-15a and miR-16 have been reported to act as tumor suppressors or potential oncomiRs in different types of cancer. This review summarizes the history, biological properties and the important functions of these two miRNAs in cancer. It also introduces their roles as regulators of immune responses and angiogenesis, endogenous controls as well as potential targets and hallmarks of cancer.

TP53 hotspot mutations are predictive of survival in primary central nervous system lymphoma patients treated with combination chemotherapy

Primary central nervous system lymphoma (PCNSL) is an aggressive variant of diffuse large B-cell lymphoma (DLBCL) confined to the CNS. TP53 mutations (MUT-TP53) were investigated in the context of MIR34A/B/C- and DAPK promoter methylation status, and associated with clinical outcomes in PCNSL patients. In a total of 107 PCNSL patients clinical data were recorded, histopathology reassessed, and genetic and epigenetic aberrations of the p53-miR34-DAPK network studied. TP53 mutational status (exon 5-8), with structural classification of single nucleotide variations according to the IARC-TP53-Database, methylation status of MIR34A/B/C and DAPK, and p53-protein expression were assessed. The 57/107 (53.2 %) patients that were treated with combination chemotherapy +/- rituximab (CCT-treated) had a significantly better median overall survival (OS) (31.3 months) than patients treated with other regimens (high-dose methotrexate/whole brain radiation therapy, 6.0 months, or no therapy, 0.83 months), P < 0.0001. TP53 mutations were identified in 32/86 (37.2 %), among which 12 patients had hotspot/direct DNA contact mutations. CCT-treated patients with PCNSL harboring a hotspot/direct DNA contact MUT-TP53 (n = 9) had a significantly worse OS and progression free survival (PFS) compared to patients with non-hotspot/non-direct DNA contact MUT-TP53 or wild-type TP53 (median PFS 4.6 versus 18.2 or 45.7 months), P = 0.041 and P = 0.00076, respectively. Multivariate Cox regression analysis confirmed that hotspot/direct DNA contact MUT-TP53 was predictive of poor outcome in CCT-treated PCNSL patients, P = 0.012 and P = 0.008; HR: 1.86 and 1.95, for OS and PFS, respectively. MIR34A, MIR34B/C, and DAPK promoter methylation were detected in 53/93 (57.0 %), 80/84 (95.2 %), and 70/75 (93.3 %) of the PCNSL patients with no influence on survival. Combined MUT-TP53 and MIR34A methylation was associated with poor PFS (median 6.4 versus 38.0 months), P = 0.0070. This study suggests that disruption of the p53-pathway by MUT-TP53in hotspot/direct DNA contact codons is predictive of outcome in CCT-treated PCNSL patients, and concomitant MUT-TP53 and MIR34A methylation are associated with poor PFS.

High-grade Transformation of Low-grade B-cell Lymphoma: Pathology and Molecular Pathogenesis

Patients with low-grade (clinically indolent) lymphomas are at risk to undergo transformation to high-grade (clinically aggressive) lymphoma, although transformation only occurs in a subset of patients. When transformation occurs it is a critical event that determines the course of disease and is associated with unfavorable patient outcomes. Accurate detection of transformation, predictive biomarkers, and identification of specific molecular pathways implicated in the pathobiology of transformation will facilitate personalized therapeutic approaches and underpin advances in clinical outcomes. In this article, we present an update of the clinical and pathologic diagnostic criteria for low-grade B-cell lymphoma transformation and discuss the molecular alterations involved in the pathogenesis of this biological phenomenon.

MicroRNAs in chronic lymphocytic leukemia: miRacle or miRage for prognosis and targeted therapies?

Chronic lymphocytic leukemia (CLL) is a heterogeneous disease and has a highly variable clinical course with survival ranging from a couple of months to several decades. MicroRNAs (miRNAs), small non-coding RNAs that regulate transcription and translation of genes, have been found to be involved in CLL initiation, progression, and resistance to therapy. In addition, they can be used as prognostic biomarkers and as targets for novel therapies. In this review, we describe the association between miRNAs and the cytogenetic aberrations commonly found in CLL, as well as with other prognostic factors. We describe the presence of miRNAs as extracellular entities in the plasma and serum of CLL patients and discuss their role in resistance to therapy. Finally, we will explore the potential of targeted miRNA therapy for the treatment of CLL, with a special emphasis on MRX34, the first miRNA mimic that is currently being evaluated for clinical use.