Burkitt lymphoma (BL) is an aggressive B cell lymphoma characterized by the reciprocal translocation of the c-Myc gene with immunoglobulin genes. Recently, MYC has been shown to maintain the neoplastic state via the miR-17-92 microRNA cluster that suppresses chromatin regulatory genes and the apoptosis regulator Bim. However, the expression and prognostic impact of miR-17-92 members in pediatric BL (pBL) are unknown. Therefore, we investigated miR-17, miR-19a, miR-19b, miR-20, and miR-92a expression and prognostic impact in a series of 41 pBL samples. In addition, Bim protein expression was evaluated and compared to miR-17, miR-19a, miR-19b, miR-20, and miR-92a levels and patient outcomes. The expression of miR-17-92 members was evaluated by qPCR and Bim protein by immunohistochemistry. Log-rank test was employed to assess prognostic impact. We found that upregulated expression of miR-17 and miR-20a correlates with lack of pro-apoptotic Bim expression. Patients bearing tumors with upregulated miR-17 displayed decreased overall survival (OS), and multivariate analysis revealed that miR-17 was a significant predictor of shortened OS. Using hairpin inhibitors, we showed that inhibition of miR-17 resulted in enhanced Bim expression in a BL cell line overexpressing the miR-17-92 cluster. Our results describe for the first time miR-17, miR-19a, miR-19b, miR-20a, and miR-92a expression profiles in pBL. The prognostic impact of miR-17 should be validated in a larger series, and may provide new therapeutic avenues in the era of anti-miRNA therapy research. Additional functional studies are further required to understand the specific role of miR-17-92 cluster members in BL.
This review summarizes recent findings on MP biogenesis and the role of the MPs cargo in cancer and discusses some of the RNAs and proteins involved. In addition, the discussion covers evidence of (1) how and which signaling pathways can be activated by MPs in recipient cells; (2) recipient cell-type selectivity in incorporation of proteins and RNAs transported by MPs; and (3) how upon stimulation, stromal cells release MPs, promoting resistance to chemotherapeutics and invasiveness in cancer cells.
Our data suggest that subcellular survivin localization and p53 expression may be employed as valuable tools to improve the accuracy of the histological sub-classification of diffuse astrocytic tumors. Patients whose tumors overexpress these proteins may benefit from radiotherapy, irrespective age and/or histological classification.
Medulloblastoma (MDB) is the most common malignant cerebellar tumor in children. Because of the significant rate of mortality and treatment-related morbidity, the identification of prognostic factors could lead to a more accurate selection of patients who can benefit from a less aggressive therapy and improve risk stratification. Survivin is an inhibitor of apoptosis protein (IAP), the expression of which has been associated with worse prognosis in MDB. However, both of its subcellular localizations may contribute to tumor progression, and ultimately, survivin subcellular localization prognostic value depends on tumor type biological features. The goal of this study was to analyze these survivin features in the pediatric MDB tumor samples and its impact on clinical outcome. Survivin expression and subcellular localization were accessed by immunohistochemistry in a series of 41 tumor samples. Kaplan-Meier survival curves were compared using the log-rank test. Survivin expression ranged from completely absent to fully present in a notably higher pattern of nuclear localization than cytoplasmic (19 of 41 versus 4 of 41, respectively). However, survivin expression and subcellular localization were not associated with five-year overall survival or metastasis status at diagnosis, which was the only statistically significant prognostic factor in our series (p = 0.008). Taken together, our results suggest that survivin expression should be further studied in large, multicenter series to determine its accurate impact on prognosis and pathobiology of pediatric MDB.
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