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New global miRSeq analysis of “miRNome”: the example of PTC and nodal metastases

ABSTRACT: The set of expressed microRNAs in a given cell type, or “miRNome”, can be explored under many different aspects. Many studies report modulations of the miRNome in a wide variety of cancers. Papillary thyroid cancer is the most prevalent type of endocrine cancer. The presence of nodal metastases increases the risk of recurrence and mortality. In our study, we performed microRNA deep sequencing (miRSeq) of 3 PTC, their matching normal tissues and nodal metastases and designed a new bioinformatic framework to analyze variations of the different aspects of the miRNome: expression profile, isomiRs and non-templated additions distributions, mutation or A-to-I RNA-editing. Furthermore, we validated our results using qRT-PCR on independent samples from 14 patients and using the collection of miRSeq data from The Cancer Genome Atlas (up to 495 miRseq of PTC). We gave a particular attention to cell content and contamination. We showed that microRNA expression profiles of thyrocytes are altered during tumorigenesis. These alterations involve known up regulations of microRNAs such as miR-146b-5p or miR-22-3p but also down regulations such as miR-7-5p, miR-7-2-5p, miR-1179 or miR-204-5p. Furthermore, some expression modulations were increased following the nodal metastatic process such as miR-7-2-3p or miR-138-1-3p. However, we did not find variations in the other aspects of the miRNome analyzed. We used our bioinformatic frameworks on the largest PTC miRSeq data collection available, to our knowledge. It allowed us, in one study on the different aspects of the miRNome, to find modulated microRNAs that could act as biomarkers of PTC.

ORGANISM(S): Homo sapiens

PROVIDER: GSE57780 | GEO | 2015/12/01

SECONDARY ACCESSION(S): PRJNA248083

REPOSITORIES: GEO

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Project description:To comprehensively characterize microRNAs (miRNA) expression and their target genes in thyroid cancer, we performed next-generation sequencing expression analysis of this disease. Recent studies have found that only the most abundant microRNAs mediate significant target suppression. We sequenced small RNA from 8 papillary thyroid carcinomas (PTC) with paired samples of normal thyroid tissue. We found that only a small set of abundant miRNAs are differentially expressed after pair-wise comparison (12 upregulated and 8 downregulated) reaching the minimum threshold amount to repress target mRNAs. We integrated computational prediction of potential targets and mRNA sequencing from the paired normal and tumor thyroid tissues from the same eight patients with PTC. The integrated analyses identified a master microRNA regulatory network in PTC that is involved in essential biological processes such as thyroid differentiation. As both mature products of miR-146b (miR-146b-5p and -3p) were among the most abundant upregulated in tumors, we unveil their target genes and found that miR-146b-3p specifically binds to the 3`UTR of PAX8 and NIS, leading to an impaired translation of the proteins and subsequently decreasing the iodide uptake of the cells. Furthermore, we show that mir-146b and PAX8 regulate each other, describing a novel regulatory circuit that determines the differentiated phenotype of PTC. In conclusion, our integrative genomic analysis uncovers the target genes of two of the most upregulated miRNAs and highlights the importance of a miR-146b3p-PAX8-NIS regulatory circuit that determines thyroid differentiation in thyroid cancer. Samples from Papillary Thyroid Carcinoma tumors (n=8) and contralateral normal thyroid tissue from the same patient (n=8) were collected at the Biobank of the Hospital Universitario La Paz (Madrid, Spain). The clinical characteristics of patients are summarized in Table S1. Surgically removed tissues were quickly frozen in liquid nitrogen until analysis. The samples were snap frozen on dry ice and stored at -80°C.

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New global miRSeq analysis of “miRNome”: the example of PTC and nodal metastases

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