The Host miR-17-92 Cluster Negatively Regulates Mouse Mammary Tumor Virus (MMTV) Replication Primarily Via Cluster Member miR-92a.

The mouse mammary tumor virus (MMTV) is a well-known causative agent of breast cancer in mice. Previously, we have shown that MMTV dysregulates expression of the host miR-17-92 cluster in MMTV-infected mammary glands and MMTV-induced tumors. This cluster, better known as oncomiR-1, is frequently dysregulated in cancers, particularly breast cancer. In this study, our aim was to uncover a functional interaction between MMTV and the cluster. Our results reveal that MMTV expression led to dysregulation of the cluster in both mammary epithelial HC11 and HEK293T cells with the expression of miR-92a cluster member being affected the most. Conversely, overexpression of the whole or partial cluster significantly repressed MMTV expression. Notably, overexpression of cluster member miR-92a alone repressed MMTV expression to the same extent as overexpression of the complete/partial cluster. Inhibition of miR-92a led to nearly a complete restoration of MMTV expression, while deletion/substitution of the miR-92a seed sequence rescued MMTV expression. Dual luciferase assays identified MMTV genomic RNA as the potential target of miR-92a. These results show that the miR-17-92 cluster acts as part of the cell's well-known miRNA-based anti-viral response to thwart incoming MMTV infection. Thus, this study provides the first evidence highlighting the biological significance of host miRNAs in regulating MMTV replication and potentially influencing tumorigenesis.

Identification and validation of miRNA-target genes network in pediatric brain tumors.

Alterations in miRNA levels have been observed in various types of cancer, impacting numerous cellular processes and increasing their potential usefulness in combination therapies also in brain tumors. Recent advances in understanding the genetics and epigenetics of brain tumours point to new aberrations and associations, making it essential to continually update knowledge and classification. Here we conducted molecular analysis of 123 samples of childhood brain tumors (pilocytic astrocytoma, medulloblastoma, ependymoma), focusing on identification of genes that could potentially be regulated by crucial representatives of OncomiR-1: miR-17-5p and miR-20a-5p. On the basis of microarray gene expression analysis and qRTPCR profiling, we selected six (WEE1, CCND1, VEGFA, PTPRO, TP53INP1, BCL2L11) the most promising target genes for further experiments. The WEE1, CCND1, PTPRO, TP53INP1 genes showed increased expression levels in all tested entities with the lowest increase in the pilocytic astrocytoma compared to the ependymoma and medulloblastoma. The obtained results indicate a correlation between gene expression and the WHO grade and subtype. Furthermore, our analysis showed that the integration between genomic and epigenetic pathways should now point the way to further molecular research.

mRNA and miRNA Expression Analyses of the MYC/E2F/miR-17-92 Network in the Most Common Pediatric Brain Tumors.

Numerous molecular factors disrupt the correctness of the cell cycle process leading to the development of cancer due to increased cell proliferation. Among known causative factors of such process is abnormal gene expression. Nowadays in the light of current knowledge such alterations are frequently considered in the context of mRNA-miRNA correlation. One of the molecular factors with potential value in tumorigenesis is the feedback loop between MYC and E2F genes in which miR-17-5p and miR-20a from the miR-17-92 cluster are involved. The current literature shows that overexpression of the members of the OncomiR-1 are involved in the development of many solid tumors. In the present work, we investigated the expression of components of the MYC/E2F/miR-17-92 network and their closely related elements including members of MYC and E2F families and miRNAs from two paralogs of miR-17-92: miR-106b-25 and miR-106a-363, in the most common brain tumors of childhood, pilocytic astrocytoma (PA), WHO grade 1; ependymoma (EP), WHO grade 2; and medulloblastoma (MB), WHO grade 4. We showed that the highest gene expression was observed in the MYC family for MYCN and in the E2F family for E2F2. Positive correlation was observed between the gene expression and tumor grade and type, with the highest expression being noted for medulloblastomas, followed by ependymomas, and the lowest for pilocytic astrocytomas. Most members of miR-17-92, miR-106a-363 and miR-106b-25 clusters were upregulated and the highest expression was noted for miR-18a and miR-18b. The rest of the miRNAs, including miR-19a, miR-92a, miR-106a, miR-93, or miR-25 also showed high values. miR-17-5p, miR-20a obtained a high level of expression in medulloblastomas and ependymomas, while close to the control in the pilocytic astrocytoma samples. miRNA expression also depended on tumor grade and histology.

miR-19 promotes the proliferation of clear cell renal cell carcinoma by targeting the FRK-PTEN axis.

BACKGROUND: The non-receptor tyrosine kinase Fyn-related kinase (FRK) has been reported to affect cell proliferation in several cancer types. However, its effect on the proliferation of clear cell renal cell carcinoma (ccRCC) remains largely unknown. PURPOSE: The objective of this study was to investigate the expression pattern and function of FRK in ccRCC. We further determined how FRK interacted with other molecules to regulate ccRCC proliferation. PATIENTS AND METHODS: The expression of FRK in ccRCC samples and paired normal renal tissues from 30 patients were analyzed by immunoblotting, immunohistochemistry and quantitative PCR. Then the role of FRK in ccRCC proliferation was analyzed by Cell Counting Kit-8, colony formation assay and EdU incorporation assay. In addition, the miRNA targeting FRK was predicted through a bioinformatic approach and validated by quantitative PCR, immunoblotting and luciferase reporter assay. Finally, the underlying mechanism of FRK regulation of ccRCC proliferation was also determined. RESULTS: Low expression of FRK was detected in ccRCC samples and predicted poor survival for ccRCC patients. FRK inhibited the proliferation of ccRCC cells via phosphorylating downstream PTEN. miR-19 was identified as a novel suppressor of FRK in renal cancer cells and it promoted the proliferation of ccRCC by inhibiting the FRK-PTEN axis. CONCLUSION: Our results unravel a new regulatory mechanism involved in ccRCC proliferation and may be useful in the identification of therapeutic targets for ccRCC.

The Oncogenic Relevance of miR-17-92 Cluster and Its Paralogous miR-106b-25 and miR-106a-363 Clusters in Brain Tumors.

The fundamental function of ribonucleic acids is to transfer genetic information from DNA to protein during translation process, however, this is not the only way connecting active RNA sequences with essential biological processes. Up until now, many RNA subclasses of different size, structure, and biological function were identified. Among them, there are non-coding single-stranded microRNAs (miRNAs). This subclass comprises RNAs of 19-25 nucleotides in length that modulate the activity of well-defined coding RNAs and play a crucial role in many physiological and pathological processes. miRNA genes are located both in exons, introns, and also within non-translated regions. Several miRNAs that are transcribed from the adjacent miRNA genes are called cluster. One of the largest ones is miR-17-92 cluster known as OncomiR-1 due to its strong link to oncogenesis. Six miRNAs from the OncomiR-1 have been shown to play important roles in various physiological cellular processes but also through inhibition of cell death in many cancer-relevant processes. Due to the origin and similarity of the sequence, miR-17-92 cluster and paralogs, miR-106b-25 and miR-106a-363 clusters were defined. Here we discuss the oncogenic function of those miRNA subgroups found in many types of cancers, including brain tumors.

Expression of oncogenic miR-17-92 and tumor suppressive miR-143-145 clusters in basal cell carcinoma and cutaneous squamous cell carcinoma.

BACKGROUND: A variety of cancers are associated with the expression of the oncogenic miR-17-92 cluster (Oncomir-1) and tumor suppressor miR-143-5p/miR-145-5p. Epidermal skin cancer has not been investigated for the expression of miR-17-92 and miR-143-145 clusters, despite being extensively studied regarding global microRNA profiles. The goal of this study was to investigate the expression and possible correlation of expression of miR17-92 and miR-143-145 cluster members in epidermal skin cancer. METHODS: We evaluated punch biopsies from patients with cutaneous squamous cell carcinoma (cSCC, n=15) and basal cell carcinoma (BCC, n=16), along with control specimens from non-lesional epidermal skin (n=16). Expression levels of the miR17-92 cluster (including miR-17-5p, miR-17-3p, miR-18a-3p, miR-18a-5p, miR-19a-3p, miR-19a-5p, miR-19b-3p, miR-19b-1-5p, miR-20a-3p, miR-20a-5p, miR-92a-3p, and miR-92a-5p) and the tumor-suppressive cluster miR-143-145 (including miR-143-5p and miR-145-5p) were detected by quantitative real-time reverse transcriptase polymerase chain reaction. RESULTS: We noted a highly significant increased expression of the miR-17-92 members miR-17-5p, miR-18a-5p, miR19a-3p, and miR-19b-3p and tumor suppressor miR-143-5p (p<0.01) in cSCC. miR-145-5p had a significantly decreased expression (p<0.05) for in BCC. A correlation analysis revealed multiple correlating miRNA-pairs within and between the investigated clusters. CONCLUSION: This study marks the first evidence for the participation of members of the miR-17-92 cluster in cSCC and miR-143-145 cluster in BCC.