Stem cells and therapeutic genes are emerging as a new therapeutic approach to treat various neurodegenerative diseases with few effective treatment options. However, potential formation of tumors by stem cells has hampered their clinical application. Moreover, adequate preclinical platforms to precisely test tumorigenic potential of stem cells are controversial. In this study, we compared the sensitivity of various animal models for in vivo stem cell tumorigenicity testing to identify the most sensitive platform. Then, tumorigenic potential of adult human multipotent neural cells (ahMNCs) immortalized by the human telomerase reverse transcriptase (hTERT) gene was examined as a stem cell model with therapeutic genes. When human glioblastoma (GBM) cells were injected into adult (4–6-week-old) Balb/c-nu, adult NOD/SCID, adult NOG, or neonate (1–2-week-old) NOG mice, the neonate NOG mice showed significantly faster tumorigenesis than that of the other groups regardless of intracranial or subcutaneous injection route. Two kinds of ahMNCs (682TL and 779TL) were primary cultured from surgical samples of patients with temporal lobe epilepsy. Although the ahMNCs were immortalized by lentiviral hTERT gene delivery (hTERT-682TL and hTERT-779TL), they did not form any detectable masses, even in the most sensitive neonate NOG mouse platform. Moreover, the hTERT-ahMNCs had no gross chromosomal abnormalities on a karyotype analysis. Taken together, our data suggest that neonate NOG mice could be a sensitive animal platform to test tumorigenic potential of stem cell therapeutics and that ahMNCs could be a genetically stable stem cell source with little tumorigenic activity to develop regenerative treatments for neurodegenerative diseases.
An unfortunate consequence of improvements in the treatments of advanced primary cancers is the concurrent increase of metastatic brain tumors. Despite of unfavorable clinical prognosis, radiation therapy is still the only viable treatment option for brain metastases. Expression of c-Met induces cell migration and invasion in many cancers, which are indispensable steps for metastasis. Accordingly, we examined the effects of gene silencing of c-Met on brain metastasis to evaluate the possibility of c-Met as a potential target. MDA-MB-435 cells were transfected with c-Met targeting short hairpin RNAs (shRNAs). Effects of c-Met shRNAs on the expression of epithelial mesenchymal transition (EMT) related proteins, in vitro migration, and in vivo brain metastasis were examined. Expression of mesenchymal markers and in vitro migration of MDA-MB-435 cells were significantly inhibited by introduction of c-Met shRNAs. When c-Met-silenced MDA-MB-435 cells were stereotactically implanted into the brains of immune-compromised mice or injected into the right internal carotid arteries, c-Met-silenced MDA-MB-435 cells produced significantly smaller tumor masses or survival time was significantly prolonged, respectively, compared with MDA-MB-435 cells transfected with control shRNA. The data reveal the novel function of c-Met in the process of brain metastasis and its potential as a preventive and/or therapeutic target in this disease. Citation Format: Se Jeong Lee, Hye Won Lee, Mi Young Song, Kee Hang Lee, Young-Eun Lee, Kyeung Min Joo. Gene silencing of c-met leads to brain metastasis inhibitory effects. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr C52.
Current in vivo model system poses limitation on fully recapitulating genomic characteristics of a tumor due to high complexity and poor understanding of the heterogeneous microenvironment conditions in cancer pathogenesis. In an effort to address such issues, strategic models are required. In present study, we propose that the most representative cancer models have consistent tumor microenvironments and genomic mutations. The Clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 system is a powerful genome editing tool for efficient and precise genome engineering. Here, we employed CRISPR-Cas9 system in vivo to generate Cre-dependent Cas9 knock-in mouse (B6;129-Gt(ROSA)26Sortm1(CAG-cas9*,-EGFP)Fezh/J, Jackson lab.). The Cre-dependent Cas9 mouse models harbor combinations of genomic alterations including well-established oncogenes such as EGFRviii, c-MET, PDGFRa, IDH1 R132H and KRAS, EGFR, ALK, BRAF in Brain and Lung cancer models, respectively. While, they also consist of tumor suppressor genes including PTEN, NF1, Ink4a/ARF, Rb, TP53 and TP53, PTEN, NKx-1, APC in both Brain and Lung models, respectively. Cre-dependent model allows us to study in-depth into the tumor initiation and progression, while able to follow up in the role of tumor microenvironment in cancer maintenance. A better understanding of cancer models for preclinical research including their uses, as well as their limitations, may aid future potential studies regarding the development and implementation of new immune targeted therapies and potential validation of novel therapeutic biomarkers. Citation Format: Da Eun Jeong, Kee Hang Lee, Sung Soo Kim, Yoon Kyung Bae, Hyun Nam, Ji Yoon Hwang, Hee Jang Pyeon, Hye Jin Song, Kyeung Min Joo. Glioblastoma animal model using CRISPR-Cas9 technology [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 797. doi:10.1158/1538-7445.AM2017-797
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