Preservation of cancer stem cell pool in primary tumor-based orthotopic xenograft models of pediatric brain tumors Free

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Animal models play crucial roles in both biological and preclinical studies of human cancers. For pediatric medulloblastoma (MB) and glioblastoma multiform (GBM), of which the clinical outcomes remain dismal, there is only limited availability of animal models that reliably reproduce the biology of these highly malignant neoplasms. To develop clinical accurate animal models, we directly injected a total of 18 fresh surgical specimens from pediatric brain tumor patients into cerebrum or cerebellum of SCID mice. Among them, 7 of the 13 MB (54%), 3 of 4 GBM (75%) and 1 atypical teratoid /rhabdoid tumor formed xenograft tumors. Many of these tumors have been serially transplanted in vivo in mouse brains for 3-12 times, and have exhibited reproducible animal survival curves. Detailed characterization of the xenografts revealed that they shared nearly identical histological and immunohistochemical features as the original tumors. Most of the xenograft tumors are highly invasive and frequently metastasize through CSF. Using 10K SNP array, we further demonstrated that xenograft tumors retained the genotypic profiles resembling that of the primary tumors. To ensure a stable and timely supply of animal models, we have optimized the protocol for long-term cryopreservation of xenograft tumor cells, and confirmed that the retrieved xenograft cells preserved both the tumorigenicity (100%) and the histological features of the original tumors. More importantly, we have demonstrated that CD133+ cancer stem cells are maintained during serial in vivo passage of the xenograft tumors. These CD133+ cells can form neurospheres in the presence of EGF and bFGF, and be induced to express markers of glial (GFAP), neuronal (MAP2) and oligoglial (O4) markers. In summary, we have developed a panel of novel orthotopic xenograft models that accurately replicate the histopathological, genetic and behavioral features of pediatric malignant brain tumors. These models should provide an avenue for biological study and preclinical drug screening of MBs and GBMs.