The Role of miRNA in Haematological Malignancy

MicroRNAs in prostate cancer following radiotherapy: Towards predicting response to radiation treatment

Prostate cancer (PCa) is the second most frequently diagnosed male cancer worldwide. Early diagnosis of PCa, response to therapy and prognosis still represent a challenge. Nearly 60% of PCa patients undergo radiation therapy (RT) which might cause side effects. In spite of numerous researches in this field, predictive biomarkers for radiation toxicity are still not elucidated. MicroRNAs as posttranscriptional regulators of gene expression are shown to be changed during and after irradiation. Manipulation with miRNA levels might be used to modulate response to RT-to reverse radioresistance-to induce radiosensitivity, or if needed, to reduce sensitivity to treatment to avoid side effects. In this review we have listed and described miRNAs involved in response to RT in PCa, and highlighted potential candidates for future biological tests predicting radiation response to RT, with the special focus on side effects of RT. Individual radiation response is a result of the interactions between physical characteristics of radiation treatment and biological background of each patient, and miRNA expression changes among others. According to described literature we concluded that let-7, miR-21, miR-34a, miR-146a, miR-155, and members of miR-17/92 cluster might be promising candidates for biological tests predicting radiosensitivity of PCa patients undergoing radiation treatment, and as future agents for modulation of radiation response. Predictive miRNA panels, especially for acute and late side effects of RT can serve as a starting point for decisions for individualized RT planning. We believe that this review might be one step closer to understanding molecular mechanisms underlying individual radiation response of patients with PCa.

LeukmiR: a database for miRNAs and their targets in acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is one of the most common hematological malignancies in children. Recent studies suggest the involvement of multiple microRNAs in the tumorigenesis of various leukemias. However, until now, no comprehensive database exists for miRNAs and their cognate target genes involved specifically in ALL. Therefore, we developed 'LeukmiR' a dynamic database comprising in silico predicted microRNAs, and experimentally validated miRNAs along with the target genes they regulate in mouse and human. LeukmiR is a user-friendly platform with search strings for ALL-associated microRNAs, their sequences, description of target genes, their location on the chromosomes and the corresponding deregulated signaling pathways. For the user query, different search modules exist where either quick search can be carried out using any fuzzy term or by providing exact terms in specific modules. All entries for both human and mouse genomes can be retrieved through multiple options such as miRNA ID, their accession number, sequence, target genes, Ensemble-ID or Entrez-ID. User can also access miRNA: mRNA interaction networks in different signaling pathways, the genomic location of the targeted regions such as 3'UTR, 5'UTR and exons with their gene ontology and disease ontology information in both human and mouse systems. Herein, we also report 51 novel microRNAs which are not described earlier for ALL. Thus, LeukmiR database will be a valuable source of information for researchers to understand and investigate miRNAs and their targets with diagnostic and therapeutic potential in ALL. Database URL: http://tdb.ccmb.res.in/LeukmiR/.

The Hedgehog signal transducer Smoothened and microRNA-326: pathogenesis and regulation of drug resistance in pediatric B-cell acute lymphoblastic leukemia

Purpose

Multidrug resistance (MDR) and the subsequent disease relapse are the major causes of childhood acute lymphoblastic leukemia (ALL) related death. The Hedgehog (Hh) signaling pathway can contribute to cancer MDR. In the current study, Smoothened (Smo) was selected as the experimental target due to its importance in the Hh pathway in order to evaluate its probable role in pediatric B-ALL drug resistance.

Patients and methods

The study included 27 pediatric B-ALL and 16 control bone marrow samples. Quantitative RT-PCR was used to investigate the expression levels of Smo and miR-326 as the key players of the Hh pathway. Western blot analysis was performed. The presence of minimal residual disease was studied using PCR-SSCP. The association between Smo expression and drug resistance was analyzed statistically.

Results

Results showed a significant increase in the Smo expression levels in drug-resistant patients in comparison with drug-sensitive children with B-ALL (P=0.0128, AUC=0.82). A considerable negative association between miR-326 and Smo expression levels was identified (r=-0.624, P=0.002). A binomial test confirmed the regulatory role of miR-326 on the translational repression of Smo (P=0.031). Statistics showed no association between Smo and ABCA2 expression levels. However, a significant positive correlation was observed between the Smo and ABCA3 transcripts in the resistant ALL children (r=0.607, P=0.016).

Conclusion

Data revealed the possible oncogenic impact of Smo on leukemogenesis and drug resistance in pediatric B-ALL. Upregulation of Smo was introduced, for the first time, as a prognostic factor for drug resistance in childhood B-ALL. To the best of our knowledge, this is the first study that shows a positive correlation between Smo and ABCA3 expression levels in pediatric B-ALL, explaining a possible mechanism for the development of drug resistance in this cancer. Moreover, the current project revealed a negative modulatory effect of miR-326 on the expression levels of Smo.

The impact of variations in transcription of DICER and AGO2 on exacerbation of childhood B-cell lineage acute lymphoblastic leukaemia

The expression of microRNA in eukaryotic cells is subject to tightly regulated processing. The altered expression of microRNAs in a number of cancers suggests their contribution to disease pathogenesis, where processing pathways may be involved in disease pathogenesis. In the present study, we evaluated changes in the profile of two main components of microRNA biogenesis, AGO2 and DICER, and assessed their correlation with disease progression in childhood acute lymphoblastic leukaemia (ALL). To achieve this aim, 25 patients afflicted with ALL were included in the study along with 25 healthy subjects as control. The expression level of AGO2 and DICER was evaluated by real-time PCR. The results revealed an increase in the expression of DICER and a decrease in AGO2 in patients. The correlation between the alteration levels of these genes with pathologic events was also studied. This increase or decrease proved to be directly correlated with the progression of the disease particularly in L1 to L2. According to the obtained results, it can be deduced that dysregulation in transcription of DICER and AGO2, involved in the formation of mature microRNAs in cytoplasm of ALL cancer cells, is a part of the pathological molecular mechanism implicated in the exacerbation of this malignancy. Therefore, the genes involved in microRNAs biogenesis that have been studied here could be considered as candidate prognostic markers especially in childhood ALL which will help towards a better understanding of the molecular basis of ALL.

Correlation analysis on the expression levels of microRNA-23a and microRNA-23b and the incidence and prognosis of ovarian cancer

The present study aimed to investigate the expression levels of microRNA (miR)-23a and miR-23b in the tumor tissues of patients with ovarian cancer. The study also explored the correlation of miR-23a and miR-23b expression levels in the tumor tissues with the clinic-pathological parameters and prognosis of the patients. Specimens of frozen tumor tissues and normal tissues adjacent to the tumor were collected from 50 patients with ovarian cancer. Reverse transcription-quantitative polymerase chain reaction was adopted to detect the expression levels of miR-23a and miR-23b in tumor tissues. Furthermore, normal tissues adjacent to the tumor were utilized as the control for the experiments and Pearson method was used to analyze the correlation between miR-23a and miR-23b expression levels in tumor tissues. The correlation of miR-23a and miR-23 expression in tumor tissues and the prognosis of the patients with ovarian cancer was analyzed in combination with clinical data. The expression of miR-23a in the tissues of ovarian cancer was significantly higher in comparison with normal adjacent tissues. However, the expression of miR-23b in the tissues of ovarian cancer was significantly lower when compared with adjacent normal tissues. Notably, the expression of miR-23a was negatively correlated with that of miR-23b in tumor tissues of ovarian cancer. The high expression of miR-23a and the low expression of miR-23b in tumor tissues of the patients was correlated with the degree of tumor differentiation, metastasis of lymph nodes and clinical staging. The five-year overall survival rate of the patients was 36% (18/50). Univariate survival analysis indicated that miR-23a and miR-23b were the factors influencing the overall survival rate of ovarian cancer. The present findings suggest that high expression of miR-23a and the low expression of miR-23b are closely correlated with the occurrence and development of ovarian cancer. The abnormal expression of the miR-23a and miR-23b could be utilized as potential prognostic molecular markers of ovarian cancer.

State of the art in microRNA as diagnostic and therapeutic biomarkers in chronic lymphocytic leukemia

Early diagnostic is one of the most important steps in cancer therapy which helps to design and choose a better therapeutic approach. The finding of biomarkers in various levels including genomics, transcriptomics, and proteomics levels could provide better treatment for various cancers such as chronic lymphocytic leukemia (CLL). The CLL is the one of main lymphoid malignancies which is specified by aggregation of mature B lymphocytes. Among different biomarkers (e.g., CD38, chromosomes abnormalities, ZAP-70, TP53, and microRNA [miRNA]), miRNAs have appeared as new diagnostic and therapeutic biomarkers in patients with the CLL disease. Multiple lines of evidence indicated that deregulation of miRNAs could be associated with pathological events which are present in the CLL. These molecules have an effect on a variety of targets such as Bcl2, c-fos, c-Myc, TP53, TCL1, and STAT3 which play critical roles in the CLL pathogenesis. It has been shown that expression of miRNAs could lead to the activation of B cells and B cell antigen receptor (BCR). Moreover, exosomes containing miRNAs are one of the other molecules which could contribute to BCR stimulation and progression of CLL cells. Hence, miRNAs and exosomes released from CLL cells could be used as potential diagnostic and therapeutic biomarkers for CLL. This critical review focuses on a very important aspect of CLL based on biomarker discovery covers the pros and cons of using miRNAs as important diagnostics and therapeutics biomarkers for this deadly disease.

Therapeutic Potential of miR-494 in Thrombosis and Other Diseases: A Review

Functional nucleic acids, such as microRNAs (miRNAs), have been implicated in the pathophysiology of many diseases. The miRNA expression profiles of various cancers including haematological malignancies are well defined, but the role of miRNAs in haemostasis and the regulation of coagulation is poorly understood. We identified that miR-494 is oestrogen responsive and directly targets the anticoagulant protein, Protein S, as a mechanism for acquiring Protein S deficiency under high oestrogenic conditions such as during pregnancy and oral contraceptive use. Furthermore, previous studies have also characterised miR-494 to be involved in many biological processes. This paper reviews the current knowledge in the role of miRNAs in regulating haemostatic proteins and the known biological functions of miR-494, highlighting miR-494 as an emerging therapeutic target, with an overview of the strategy we have employed in identifying functional nucleic acids such as miRNAs that target haemostatic factors and the therapeutic potential of miR-494-directed therapy for the treatment of thrombotic disorders.

Multiple myeloma cells modify VEGF/IL-6 levels and osteogenic potential of bone marrow stromal cells via Notch/miR-223

Bone marrow mesenchymal stromal cells (BMMSCs) represent a crucial component of multiple myeloma (MM) microenvironment supporting its progression and proliferation. Recently, microRNAs have become an important point of interest for research on micro-environmental interactions in MM with some evidence of tumor supportive roles in MM. In this study, we examined the role of miR-223 for MM support in BMMSCs of 56 patients with MM (MM-BMMSCs). miR-223 expression in MM-BMMSCs was reduced by the presence of MM cells in vitro in a cell-contact dependent manner compared to mono-cultured MM-BMMSCs. Co-cultivation of MM cells and MM-BMMSCs induced activation of notch amongst others via jagged-2/notch-2 leading to increased expression of Hes1, Hey2, or Hes5 in both cell types. Cultivation of MM-BMMSCs with increasing levels of recombinant jagged-2 reduced miR-223 and increased Hes1 levels in a concentration-dependent manner. Transient reduction of miR-223 levels increased VEGF and IL-6 expression and secretion by MM-BMMSCs. In addition, reduction of miR-223 degraded the osteogenic differentiation potential of MM-BMMSCs. Inhibition of notch signaling induced apoptosis in both MM cells and MM-BMMSCs. Furthermore, it increased miR-223 levels and reduced expression of VEGF and IL-6 by both cell types. These data provide first evidence that miR-223 participates in different MM supporting pathways in MM-BMMSCs inlcuding regulation of cytokine secretion and expression as well as osteogenic differentiation of MM-BMMSCs. More insights on the role of miR-223 in MM-BMMSCs and in cellular interactions between MM cells and MM-BMMSCs could provide starting points for a more efficient anti-myeloma treatment by targeting of notch signaling. © 2015 Wiley Periodicals, Inc.

miR-382 inhibits migration and invasion by targeting ROR1 through regulating EMT in ovarian cancer

Increasing evidence suggests that microRNAs (miRNAs) play a critical role in tumorigenesis. Decreased expression of miR‑382 has been observed in various types of cancers. However, the biological function of miRNA-382 in ovarian cancer is still largely unknown. Here, we found miR‑382 was downregulated in human ovarian cancer tissues and cell lines. miR‑382 inhibited ovarian cancer cell proliferation, migration, invasion and the epithelial-mesenchymal transition (EMT). Furthermore, we identified receptor tyrosine kinase orphan receptor 1 (ROR1) as a target of miR‑382, and miR‑382 rescued the promotion effect of ROR1 on migration, invasion and EMT process in SKOV3 and COV434 cells. Collectively, these findings revealed that miR‑382 inhibits migration and invision by targeting ROR1 through regulating EMT in ovarian cancer, and might serve as a tumor suppressor in ovarian cancer.

CD44, Hyaluronan, the Hematopoietic Stem Cell, and Leukemia-Initiating Cells

CD44 is an adhesion molecule that varies in size due to glycosylation and insertion of so-called variant exon products. The CD44 standard isoform (CD44s) is highly expressed in many cells and most abundantly in cells of the hematopoietic system, whereas expression of CD44 variant isoforms (CD44v) is more restricted. CD44s and CD44v are known as stem cell markers, first described for hematopoietic stem cells and later on confirmed for cancer- and leukemia-initiating cells. Importantly, both abundantly expressed CD44s as well as CD44v actively contribute to the maintenance of stem cell features, like generating and embedding in a niche, homing into the niche, maintenance of quiescence, and relative apoptosis resistance. This is surprising, as CD44 is not a master stem cell gene. I here will discuss that the functional contribution of CD44 relies on its particular communication skills with neighboring molecules, adjacent cells and, last not least, the surrounding matrix. In fact, it is the interaction of the hyaluronan receptor CD44 with its prime ligand, which strongly assists stem cells to fulfill their special and demanding tasks. Recent fundamental progress in support of this “old” hypothesis, which may soon pave the way for most promising new therapeutics, is presented for both hematopoietic stem cell and leukemia-initiating cell. The contribution of CD44 to the generation of a stem cell niche, to homing of stem cells in their niche, to stem cell quiescence and apoptosis resistance will be in focus.

PLC-beta 1 regulates the expression of miR-210 during mithramycin-mediated erythroid differentiation in K562 cells

PLC-beta 1 (PLCβ1) inhibits in human K562 cells erythroid differentiation induced by mithramycin (MTH) by targeting miR-210 expression. Inhibition of miR-210 affects the erythroid differentiation pathway and it occurs to a greater extent in MTH-treated cells. Overexpression of PLCβ1 suppresses the differentiation of K562 elicited by MTH as demonstrated by the absence of γ-globin expression. Inhibition of PLCβ1 expression is capable to promote the differentiation process leading to a recovery of γ-globin gene even in the absence of MTH. Our experimental evidences suggest that PLCβ1 signaling regulates erythropoiesis through miR-210. Indeed overexpression of PLCβ1 leads to a decrease of miR-210 expression after MTH treatment. Moreover miR-210 is up-regulated when PLCβ1 expression is down-regulated. When we silenced PKCα by RNAi technique, we found a decrease in miR-210 and γ-globin expression levels, which led to a severe slowdown of cell differentiation in K562 cells and these effects were the same encountered in cells overexpressing PLCβ1. Therefore we suggest a novel role for PLCβ1 in regulating miR-210 and our data hint at the fact that, in human K562 erythroleukemia cells, the modulation of PLCβ1 expression is able to exert an impairment of normal erythropoiesis as assessed by γ-globin expression.

Expression pattern of key microRNAs in patients with newly diagnosed chronic myeloid leukemia in chronic phase

INTRODUCTION

Chronic myeloid leukemia (CML) is caused by reciprocal translocation in hematopoietic stem cells (HSCs). This translocation forms the BCR-ABL1 oncogene, which alters several signaling pathways that control malignancy. CML has three phases: chronic, accelerated, and blast crisis. The microRNAs (miRNAs or miRs) are noncoding RNAs that downregulate their target gene by targeting 3' UTR of mRNA or through translational inhibition. It has been shown that miRNAs regulate many biological processes, and dysregulation of these regulatory RNAs is involved in disease development, particularly in cancer. The important role of miRNAs as therapeutic agents and biomarkers has been demonstrated in CML patients at different phases of the disease.

METHODS

Stem-loop reverse transcription polymerase chain reaction was used to characterize differentially expressed miRNAs of leukocytes in the peripheral blood of 50 newly diagnosed CML patients in chronic phase.

RESULTS

Some onco-miRNAs were found to be downregulated (miR-155 and miR-106), and some tumor suppressor miRs (miR-16-1, miR-15a, miR-101, miR-568) were upregulated.

CONCLUSION

These results show that very few miRNAs alone would be good candidates for CML diagnosis independently of conflicting results, but together could be an additional tool for CML diagnosis. Moreover, miRNAs might be good candidates for prognosis prediction and CML therapy.

Serum miR-224 reflects stage of hepatocellular carcinoma and predicts survival

Background. In our previous study, we conducted a systematic screening of miRNA to identify potential serum biomarkers for predicting venous metastasis and survival in patients with hepatocellular carcinoma (HCC). miR-224 was one of the differentially expressed miRNAs. This study aimed to confirm whether serum miR-224 level is associated with the presence of venous metastasis and survival. Methods. TaqMan miRNA probe was used to perform qRT-PCR assays to evaluate the expression of serum miR-224 in a cohort of 182 HCC patients. Results. Patients with high miR-224 serum level showed poor survival compared to that with low miR-224 serum level (HR 1.985; 95% CI, 1.08, 3.65, P = 0.027). The serum miR-224 levels were significantly higher in the BCLC stage C patients compared with the stage B patients (P = 0.005). In further analysis, significant difference of serum miR-224 expression level was observed when patients grouped by the status of PVTT but not the status of extra-liver metastasis (P = 0.013 and P = 0.091). Serum levels of miR-224 showed significant relation with parameters of liver damage and serum AFP. Conclusion. Serum miR-224 might be BCLC stage dependent. It can reflect the status of tumor and liver damage. It was an independent predictor for the survival of HCC patients.

Molecular mechanisms underlying the role of microRNAs in the chemoresistance of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is an extremely severe disease where the mortality and incidence rates are almost identical. This is mainly due to late diagnosis and limited response to current treatments. The tumor macroenvironment/microenvironment have been frequently reported as the major contributors to chemoresistance in PDAC, preventing the drugs from reaching their intended site of action (i.e., the malignant duct cells). However, the recent discovery of microRNAs (miRNAs) has provided new directions for research on mechanisms underlying response to chemotherapy. Due to their tissue-/disease-specific expression and high stability in tissues and biofluids, miRNAs represent new promising diagnostic and prognostic/predictive biomarkers and therapeutic targets. Furthermore, several studies have documented that selected miRNAs, such as miR-21 and miR-34a, may influence response to chemotherapy in several tumor types, including PDAC. In this review, we summarize the current knowledge on the role of miRNAs in PDAC and recent advances in understanding their role in chemoresistance through multiple molecular mechanisms.

MicroRNAs in personalized cancer therapy

MicroRNAs (miRNAs) are small endogenous noncoding single-stranded RNAs. They critically regulate the post-transcriptional activity of several key physiological and pathological cell processes including cancer. Through their transcriptional regulatory functions, miRNAs control tumor proliferation, invasion and metastasis. The expression of miRNAs is altered in malignancies. It could be either upregulated or downregulated depending upon the role of a particular miRNA in the pathogenetic development of the tumor. The upregulated miRNAs exert an 'oncogenic' effect leading to tumor proliferation and metastasis. The downregulated miRNAs have 'tumor suppressor' effects. Recent studies have demonstrated that miRNAs have a role in the early diagnosis, prognosis and treatment outcome assessment of cancers. Every tumor has specific miRNA alterations, i.e. some are overexpressed and others are downregulated. These altered miRNAs can be used as a tumor-specific 'signature' for potential clinical use in improving the accuracy of diagnosis, determining prognosis and as therapeutic targets for therapy. Specific miRNAs can be targeted using oligonucleotide sequences corresponding to the altered miRNAs. These are referred to as 'antagomirs'. Depending upon the miRNA alterations in the tumor of an individual patient, one could design targeted therapies for personalized medicine in patients. Hence, miRNAs have an immense role in personalized cancer therapy.