Project description:Background: Malignant peripheral nerve sheath tumors (MPNST) are soft-tissue sarcomas that can arise either sporadically or in association with neurofibromatosis type 1 (NF1). These aggressive malignancies confer poor survival, with no effective therapy available. Methods: We generated five patient-derived MPNST orthoxenograft models (three NF1-related and two sporadic) and performed an exhaustive histological and molecular characterization of primary MPNSTs and their corresponding orthoxenografts. Finally, orthoxenografts models were used as an in vivo pre-clinical platform to test several treatment strategies. Results: MPNST orthoxenografts recapitulate the histopathological properties and preserve the genomic and transcriptomic status of their parental primary tumors. Additionally, they mimic distal dissemination properties in mice. Compatible with an origin in a catastrophic event and subsequent stabilization, MPNSTs contained highly altered genomes that remained remarkably stable in orthoxenograft establishment and along passages. Although preliminary, the results presented here point to clear differences between NF1-associated and sporadic MPNSTs. In accordance, mutation frequency in sporadic MPNSTs was an order of magnitude higher than in NF1-associated MPNSTs and unsupervised cluster analysis and principal component analysis (PCA) using a MPNST signature perfectly divided the samples between NF1 and sporadic MPNST. Finally, different therapeutic approaches tested in the validated orthoxenograft MPNST models, reveal that sorafenib, or in combination with doxorubicin or rapamycin caused a great tumor reduction in all models. Conclusion: The development of a well-characterized and standardized preclinical model for MPNSTs has laid the foundations for evaluating novel therapeutic strategies in the clinical setting. Moreover, results obtained strongly support the clinical evaluation of Sorafenib in this subset of patients. Primary MPNSTs were implanted in the sciatic nerve of nude mices to create orthoxenograft MPNST models. Several orthoxenograft passages were created. The primary tumor (when available) and passages 1 and 4 were selected for gene expression profiling to demonstrate that the orthoxenografts closely resemble their primary tumors and are stable along xenograft passages.

Project description:Malignant peripheral nerve sheath tumors (MPNST) are aggressive cancers that occur spontaneously (sporadic MPNST) or from pre-existing, benign plexiform neurofibromas in neurofibromatosis type 1 (NF1) patients. MPNSTs metastasize easily, are resistant to therapeutic intervention and are frequently fatal. The molecular changes underlying the transition to malignancy in the NF1 setting are incompletely understood. Here we investigate the involvement of microRNAs in this process. Using an RT-PCR platform microRNA expression profiles were determined from a unique series of archival paired samples of plexiform neurofibroma and MPNST. At least 90 differentially expressed microRNAs (p<0.025; FDR<10%) were identified between the paired samples. Most microRNAs (91%) were found downregulated and 9% of the microRNAs were upregulated in MPNST. Based on the fold changes and statistical significance three downregulated microRNAs (let-7b-5p, miR-143-3p, miR-145-5p) and two upregulated microRNAs (miR135b-5p and miR-889-3p) were selected for further functional characterization. Their expression levels were validated in a relevant cell line panel and a series of unpaired fresh frozen tumor samples containing plexiform neurofibromas, atypical neurofibromas and MPNSTs. As part of the validation process we also determined and analyzed microRNA expression profiles of sporadic MPNSTs observing that microRNA expression discriminates NF1-associated and sporadic MPNSTs emphasizing their different etiologies. The involvement of microRNAs in tumorigenesis and cancer progression was examined in NF1-derived MPNST cell lines through modulating microRNA levels by transient transfection of microRNA mimics or inhibitors. The effects of microRNAs on cellular proliferation, migration, invasion and Wnt/ẞ-catenin signaling were determined. Our findings indicate that, some of the selected microRNAs affect migratory and invasive capabilities and Wnt signaling activity. It was observed that the functional effects upon microRNA modulation are distinct in different cell lines. From our study we conclude that miRNAs play essential regulatory roles in MPNST facilitating tumor progression.

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Effective sorafenib treatment response in a panel of genomically-characterized malignant peripheral nerve sheath tumor orthoxenograft models

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