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Brain tumors are the leading cause of cancer related death in children, and there is biological differences between treatment naïve tumors and their therapy resistant relapses. As surgery is rarely an option for terminal brain tumors that have failed existing therapies, autopsy is frequently the only chance to obtain tumor tissues. Despite the urgent need of models of terminal brain tumors, it remains unknown if autopsied tumors can be used for in vitro and in vivo model development. To determine if (some) tumor cells can survival postmortem anoxia/starvation to proliferate in vitro and, more importantly, to form orthotopic xenograft tumors, we collected 29 autopsied brain tumors, including 15 diffuse intrinsic pontine gliomas (DIPG), 7 glioblastomas (GBM), 4 medulloblastomas (MB), 2 ependymoma and 1 atypical teratoid/rhabdoid tumor (ATRT), and made the following discoveries. i) A small fraction of tumor cells exhibited strong survival capacity and remained viable, ranging from 0.5%-40% (13.5% ± 10.9%), in tumors harvested 5-72 hrs (31.2 ± 25 hrs) after patients’ death. Cell viability, however, did not appear to be strictly correlated with the length of autopsy time (r = 0.17), suggesting that ample time should be given to the families to say goodbye to their loved ones. ii) While many autopsied tumor cells appear to have stayed alive for short terms in culture, only one pair of permanent lines (monolayer in FBS media and neurosphere in serum-free media) were established from a GBM tumor. iii) Direct implantation of tumor cells into matched locations in the brains of SCID mice led to the formation of xenograft tumors in 17 of 22 tumors (7 additional tumors are still pending). 8 of the 17 autopsy derived orthotopic (ADOX) models have been subtransplanted in mouse brains for > 3 times (5 DIPGs and 1 each of GBM, MB and ATRT). Detailed characterization confirmed their replication of histopathological features and genetic/genomic abnormalities of the patient tumors. iv) To identify the cellular origin of surviving patient tumor cells that propagated ADOX model formation, time course analysis of putative cancer stem cells (CD133, CD15, CD24/CD44, CD57, CD117) was performed. CD57+ tumor cells were found to be the most abundant subpopulations in the autopsied tumors, and their fractions increased in the ADOX tumors during serial subtransplantations. Additionally, CD57+ cells alone were able to form orthotopic xenografts, establishing their role as cancer stem cells. In conclusion, we have demonstrated that a fraction of tumor cells can survive the lengthy period of postmortem anoxia/starvation and regain tumorigenic capabilities in mouse brains; and identified CD57 as a new marker of the therapy-resistant cells with extraordinary survival and tumorigenic (TREST) capabilities. This novel panel of ADOX models should facilitate biological studies and preclinical drug screening of therapy-resistant pediatric brain tumors. Citation Format: Lin Qi, Baxter A. Patricia, Kogiso Mari, Du Yuchen, Lindsay Holly, Liu Zhigang, Xiumei Zhao, Yujing Zhang, Jack MF Su, Adekunle Adesina, Andrew W. Walter, Jeffery Murray, Rene McNall-Knapp, Javad Nazarian, Will Parsons, Murali Chintagumpala, Susan Blaney, Xiao-Nan Li. Autopsy derived orthotopic xenograft (ADOX) mouse models for terminal pediatric brain tumors. [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 1450. doi:10.1158/1538-7445.AM2015-1450

Background: MET amplification (METamp) occurs in 1-5% of treatment-naïve or 5-20% of epidermal growth factor receptor tyrosine kinase inhibitors-treated lung cancers (LC). It is a promising therapeutic target in LC. Although fluorescence in situ hybridization (FISH), next-generation sequencing (NGS), and immunohistochemical staining (IHC) are available for METamp detection, but the most appropriate detection method and criteria for defining METamp are uncertain. Here, we explored the concordance of these three methods in informing METamp status and identified patients likely to benefit from MET inhibitors. Methods: Tissue samples from LC patients who underwent MET detection by FISH, NGS, and IHC tests at Shanghai Chest Hospital were retrospectively collected. MET focal amplification and polysomy by FISH were determined as MET/CEP7 ratio ≥ 2, and < 2 with the average MET signals per cell ≥ 5, respectively. NGS-based MET focal amplification and polysomy were determined with in-house scripts (Burning Rock Biotech). Focal amplification and polysomy were defined as METamp-positive. IHC-based MET positive was determined with H-score ≥ 200. FISH was used as a reference. Results: A total of 231 patients with a median age of 65 years were enrolled. With FISH as reference testing, NGS detection for METamp showed 66.9% (87/130) sensitivity and 95.1% sensitivity (96/101), and IHC had 71.5% (93/130) sensitivity and 91.1% (92/101) specificity. Furthermore, NGS detection for MET focal amplification achieved 87.2% (75/86) sensitivity and 96.6% (140/145) specificity, while MET polysomy detection showed 20.5% (9/44) sensitivity and 98.4% (184/187) specificity. Of 153 treatment-naïve patients, patients with focal amplification (FISH: 16.7%; NGS: 16.3%) had a significantly lower frequency of classic LC oncogene alterations than those with polysomy (FISH: 51.6%, p = 0.001; NGS: 58.3%, p = 0.006) and METamp-negative patients (METneg; FISH: 72.1%, p < 0.001; NGS: 64.1%, p < 0.001). A total of 27 patients had follow-up data. The disease control rate (DCR) to MET inhibitors was 73.1% (19/26) for overall METamp, 81.0% (17/21) for focal amplification, and 40.0% (2/5) for polysomy using FISH results. In contrast, corresponding DCRs using NGS results were 84.2% (16/19), 88.9% (16/18), and 0% (0/1), respectively. Moreover, patients with NGS-based focal amplification had a significantly longer progression-free survival (PFS) than those with polysomy or METneg. Of note, 1 patient with METneg by FISH was determined to harbor focal amplification by NGS and achieved partial response to crizotinib with a PFS of 314 days. Conclusion: Our results suggest that MET focal amplification leads to oncogenic MET addiction and is associated with promising efficacy of MET inhibitors. MET focal amplification by NGS tests might be a feasible and powerful biomarker to identify LC patients who benefit from MET inhibitors. Citation Format: Chan Xiang, Lianying Guo, Ruiying Zhao, Haohua Teng, Zhou Zhang, Ting Kuang, Xinze Lv, Ting Hou, Chenglin Liu, Wenjie Sun, Haiwei Du, Yuchen Han. Next-generation sequencing-based MET focal amplification can predict treatment efficacy of MET inhibitors in lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2133.