Abstract 4433: Deregulated microRNAs in NF1 derived malignant peripheral nerve sheath tumors (MPNST) and their role in carcinogenesis

Abstract

Abstract Background and aim: MPNSTs are rare and highly aggressive soft tissue sarcomas that can occur spontaneously (sporadic MPNST) or from pre-existing plexiform neurofibromas in neurofibromatosis type 1 (NF1) patients. MPNSTs are usually diagnosed relatively late, metastasize easily, are resistant to therapeutic intervention and frequently fatal for the patient. Diagnostic biomarkers that detect early malignant transformation in the NF1 setting as well identification of putative targets for treatment are urgently needed. In this context we investigated the miRNA expression profiles in NF1-derived MPNST. Materials and Methods: Total RNA was isolated from sections of formalin fixed paraffin embedded (FFPE) tumor samples. miRNA expression was determined using a RT-PCR platform (TaqMan® Low Density Array Human MicroRNA Cards; Applied Biosystems). The expression of selected miRNAs was transiently modulated in neurofibroma and MPNST cell lines by transfection with miRNA mimics (Dharmacon) or LNA™ based anti-miRs (Exiqon) and effects on cell proliferation, invasion/migration and Wnt/β-catenin signaling were studied. Results: In order to identify miRNAs that are specifically deregulated in MPNST we analyzed miRNA expression in a unique set paired tumor samples (n=9) of plexiform neurofibroma and MPNST which were derived from the same NF1 patient. At least 90 miRNAs were found to be differentially expressed (FDR <10%; p<0.025) between neurofibromas and MPNST; the vast majority (82/90) of miRNAs being downregulated in MPNST. Interestingly, and in contrast to reports in the literature, sporadic MPNST samples (n=10) could be easily discriminated from NF1-derived MPNST by their miRNA expression profiles. On the basis of their statistical significance, fold difference and expression level, we selected miRNAs to examine their role in MPNST pathogenesis. MiRNA levels were modulated in MPNST (ST88-14, sNF96.2, 90-8TL) and neurofibroma (Hs53.T) cell lines using miRNA mimics for let-7b, miR-16, miR-26a, miR-29a, miR-139-5p, miR-146a and antisense inhibitors for miR-889, miR-135b. The effects of miRNA expression levels on cellular proliferation, invasion and migration were determined. As Wnt/β-catenin signaling is considered a cancer related driver pathway in MPNST we also investigated whether differentially expressed miRNAs could regulate this pathway focusing on miRNA previously linked to Wnt regulation or predicted to target Wnt signaling components. Using TOP/FOP luciferase reporter assays we analyzed the effects of miR-135b, miR-30a, miR-139-5p and miR-146a. Conclusion: miRNAs specifically deregulated in MPNST may fulfil key oncogenic roles and may be used as biomarker or for therapeutic purposes. Citation Format: Azadeh Amirnasr, Patricia F. van Kuijk, Robert M. Verdijk, Walter Taal, Stefan Sleijfer, Erik A. C. Wiemer. Deregulated microRNAs in NF1 derived malignant peripheral nerve sheath tumors (MPNST) and their role in carcinogenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4433. doi:10.1158/1538-7445.AM2017-4433