RESUMO
Wilms tumor (WT) is the most frequently diagnosed malignant renal tumor in children. With current treatments, ~90% of children diagnosed with WT survive and generally present with tumors characterized by favorable histology (FHWT), whereas prognosis is poor for the remaining 10% of cases where the tumors are characterized by cellular diffuse anaplasia (DAWT). Relatively few studies have investigated microRNA-related epigenetic regulation and its relationship with altered gene expression in WT. Here, we aim to identify microRNAs differentially expressed in WT and describe their expression in terms of cellular anaplasia, metastasis, and association with the main genetic alterations in WT to identify potential prognostic biomarkers. Expression profiling using TaqMan low-density array was performed in a discovery cohort consisting of four DAWT and eight FHWT samples. Relative quantification resulted in the identification of 109 (48.7%) microRNAs differentially expressed in both WT types. Of these, miR-10a-5p, miR-29a-3p, miR-181a-5p, miR-200b-3p, and miR-218-5p were selected and tested by RT-qPCR on a validation cohort of 53 patient samples. MiR-29a and miR-218 showed significant differences in FHWT with low (P = 0.0018) and high (P = 0.0131) expression, respectively. To discriminate between miRNA expression FHWTs and healthy controls, the receiver operating characteristic (ROC) curves were obtained; miR-29a AUC was 0.7843. Furthermore, low expression levels of miR-29a and miR-200b (P = 0.0027 and P = 0.0248) were observed in metastatic tumors. ROC curves for miR-29a discriminated metastatic patients (AUC = 0.8529) and miR-200b (AUC = 0.7757). To confirm the differences between cases with poor prognosis, we performed in situ hybridization for three microRNAs in five DAWT and 17 FHWT samples, and only significant differences between adjacent tissues and FHWT tumors were found for miR-181a, miR-200b, and miR-218, in both total pixels and nuclear analyses. Analysis of copy number variation in genes showed that the most prevalent alterations were WTX (47%), IGF2 (21%), 1q (36%) gain, 1p36 (16%), and WTX deletion/1q duplicate (26%). The five microRNAs evaluated are involved in the Hippo signaling pathway and participate in Wilms tumor development through their effects on differentiation, proliferation, angiogenesis, and metastasis.
RESUMO
PURPOSE: MicroRNAs were identified as molecules that participate in gene regulation; alterations in their expression characterize central nervous system (CNS). Information in pediatrics is scarce, so the objective of this work was to determine and then compare the patterns of expression of microRNAs in astrocytomas, ependymomas, and medulloblastomas, as well as in non-neoplastic brain. METHODS: Low-density arrays were utilized to evaluate 756 microRNAs in three samples of each type of tumor and non-neoplastic brain. The relative expression was calculated in order to identify the three microRNAs whose expression was modified notably. This was verified using RT-qPCR in more number of tumor samples. RESULTS: The microRNAs selected for testing were miR-100-5p, miR-195-5p, and miR-770-5p. A higher expression of miR-100-5p was observed in the astrocytomas and ependymomas compared to the medulloblastomas: on average 3.8 times (p < 0.05). MiR-770-5p was expressed less in medulloblastomas compared to astrocytomas four times (p = 0.0162). MiR-195-5p had a low expression in medulloblastomas compared to non-neoplastic cerebellum (p = 0.049). In all three tumor types, expression of miR-770-5p was lower than in non-neoplastic brain (p < 0.001). CONCLUSIONS: These microRNAs may represent potential markers in these tumors.