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Malignant Peripheral Nerve Sheath Tumors (MPNSTs) are highly resistant sarcomas that occur in up to 13% of individuals with Neurofibromatosis Type 1 (NF1). Genomic analysis of longitudinally collected tumor samples in a case of MPNST disease progression revealed early hemizygous microdeletions in NF1 and TP53, with progressive amplifications of MET, HGF, and EGFR. To examine the role of MET in MPNST progression, we developed mice with enhanced MET expression and Nf1 ablation (Nf1fl/KO;lox-stop-loxMETtg/+;Plp-creERTtg/+; referred to as NF1-MET). NF1-MET mice express a robust MPNST phenotype in the absence of additional mutations. A comparison of NF1-MET MPNSTs with MPNSTs derived from Nf1KO/+;p53R172H;Plp-creERTtg/+ (NF1-P53) and Nf1KO/+;Plp-creERTtg/+ (NF1) mice revealed unique Met, Ras, and PI3K signaling patterns. NF1-MET MPNSTs were uniformly sensitive to the highly selective MET inhibitor, capmatinib, whereas a heterogeneous response to MET inhibition was observed in NF1-P53 and NF1 MPNSTs. Combination therapy of capmatinib and the MEK inhibitor trametinib resulted in reduced response variability, enhanced suppression of tumor growth, and suppressed RAS/ERK and PI3K/AKT signaling. These results highlight the influence of concurrent genomic alterations on RAS effector signaling and therapy response to tyrosine kinase inhibitors. Moreover, these findings expand our current understanding of the role of MET signaling in MPNST progression and identify a potential therapeutic niche for NF1-related MPNSTs.

Genetically engineered mouse models (GEMMs) that employ site-specific recombinase (SSR) technology are important tools for pre-clinical studies, but this approach is costly and time-consuming. Here, we show that the CRISPR/Cas9 system can be used to efficiently complement existing GEMMs of sarcoma and generate primary sarcomas in wild type mice. Mice with the genotype KrasLSL-G12D/+; Rosa26LSL-Cas9-EGFP/+ received intramuscular delivery of an adenovirus expressing Cre recombinase and a single guide RNA (sgRNA) targeting Trp53. Cre-mediated expression of oncogenic Kras and Cas9, in combination with CRISPR/Cas9-mediated knockout of Trp53, was sufficient to generate primary soft tissue sarcomas. These tumors arose with kinetics similar to those generated using the Cre-loxP system to activate oncogenic Kras and delete Trp53 alleles. Additionally, we injected an adenovirus containing Cas9 and sgRNAs targeting Nf1 and Trp53 into the sciatic nerve of wild type mice. These mice formed malignant peripheral nerve sheath tumors (MPNSTs) in the same timeframe as MPNSTs generated using the Cre-loxP system to delete Nf1 and Ink4a/Arf alleles in GEMMs. These data demonstrate that CRISPR/Cas9 can be used to generate soft tissue sarcomas in wild type mice. Moreover, these results suggest that this technology can complement existing GEMMs for rapid assessment of tumor-modifying genes. These tools should decrease the time and expense associated with employing autochthonous mouse models of sarcoma for preclinical research. Citation Format: Jianguo Huang, Mark Chen, Melodi J. Whitley, Hsuan-Cheng Kuo, Andrea Walens, Yvonne M. Mowery, David V. Mater, William Eward, Diana M. Cardona, Lixia Luo, Yan Ma, Christopher E. Nelson, Jacqueline N. Robinson-Hamm, Charles A. Gersbach, Rebecca D. Dodd, David G. Kirsch. Using CRISPR/Cas9 to generate primary soft tissue sarcoma in genetically engineered and wild-type mice [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 2810. doi:10.1158/1538-7445.AM2017-2810

Some patients with soft-tissue sarcoma (STS) report a history of injury at the site of their tumor. Although this phenomenon is widely reported, there are relatively few experimental systems that have directly assessed the role of injury in sarcoma formation. We recently described a mouse model of STS whereby p53 is deleted and oncogenic Kras is activated in muscle satellite cells via a Pax7CreER driver following intraperitoneal injection with tamoxifen. Here, we report that after systemic injection of tamoxifen, the vast majority of Pax7-expressing cells remain quiescent despite mutation of p53 and Kras. The fate of these muscle progenitors is dramatically altered by tissue injury, which leads to faster kinetics of sarcoma formation. In adult muscle, quiescent satellite cells will transition into an active state in response to hepatocyte growth factor (HGF). We show that modulating satellite cell quiescence via intramuscular injection of HGF increases the penetrance of sarcoma formation at the site of injection, which is dependent on its cognate receptor c-MET. Unexpectedly, the tumor-promoting effect of tissue injury also requires c-Met. These results reveal a mechanism by which HGF/c-MET signaling promotes tumor formation after tissue injury in a mouse model of primary STS, and they may explain why some patients develop a STS at the site of injury. Cancer Res; 75(3); 605–14. ©2014 AACR.

Intra-operative detection of residual cancer in the tumor bed can be used to decrease the risk of a positive surgical margin, reduce the rate of re-excision, and tailor adjuvant therapy. LUM015 is a pegylated protease-activated imaging agent containing a near infrared fluorophore and quencher attached by a polypeptide linker. Using mouse models of soft tissue sarcoma (STS), we showed that LUM015 selectively localizes to the tumor and upon cleavage of the linker by proteases in the tissue, the quencher is released, allowing fluorescence to be detected. We recently completed a phase I clinical trial to test the safety of LUM015 in human patients with cancer. This open-label nonrandomized trial compared 3 dose cohorts (0.5, 1.0, and 1.5 mg/kg) of LUM015 in order to determine a safe dose of LUM015 that labels tumors in humans. A total of 15 subjects, 12 with STS and 3 with breast cancer, received IV LUM015 prior to surgical resection without any adverse pharmacological activity (APA). Quantitative fluorescence imaging of the resected tissues revealed that tumor fluorescence was significantly higher than corresponding normal tissue from the same patient (p We conducted comparative analyses of LUM015 pharmacodynamics in mouse and human subjects showing that biodistribution into tumors and activation by proteases is conserved across species. These studies revealed the presence of a novel, small molecule metabolite that correlates strongly with tissue fluorescence. Additional in vivo studies in mice and in vitro studies with mouse and human tissues showed that LUM015 is selectively distributed to and accumulates in tumors to result in increased fluorescence when compared to normal tissues. Citation Format: Melodi J. Whitley, Diana M. Cardona, Dan G. Blazer, Shelley Hwang, Rachel A. Greenup, Paul J. Mosca, Joan Cahill, Jeffrey K. Mito, Kyle C. Cuneo, Nicole Larrier, Erin O'Reilly, Ivan Spasojevic, Richard F. Riedel, William C. Eward, Linda G. Griffith, Moungi G. Bawendi, Jorge Ferrer, David B. Strasfeld, W. David Lee, Brian Brigman, David G. Kirsch. Intraoperative molecular imaging with protease-activated fluorescent imaging agents. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr SY36-03. doi:10.1158/1538-7445.AM2015-SY36-03