Genetically engineered rat gliomas: PDGF-driven tumor initiation and progression in tv-a transgenic rats recreate key features of human brain cancer

Abstract

Previously rodent preclinical research in gliomas frequently involved implantation of cell lines such as C6 and 9L into the rat brain. More recently, mouse models have taken over, the genetic manipulability of the mouse allowing the creation of genetically accurate models outweighed the disadvantage of its smaller brain size that limited time allowed for tumor progression. Here we illustrate a method that allows glioma formation in the rat using the replication competent avian-like sarcoma (RCAS) virus / tumor virus receptor-A (tv-a) transgenic system of post-natal cell type-specific gene transfer. The RCAS/tv-a model has emerged as a particularly versatile and accurate modeling technology by enabling spatial, temporal, and cell type-specific control of individual gene transformations and providing de novo formed glial tumors with distinct molecular subtypes mirroring human GBM. Nestin promoter-driven tv-a (Ntv-a) transgenic Sprague-Dawley rat founder lines were created and RCAS PDGFA and p53 shRNA constructs were used to initiate intracranial brain tumor formation. Tumor formation and progression were confirmed and visualized by magnetic resonance imaging (MRI) and spectroscopy. The tumors were analyzed using histopathological and immunofluorescent techniques. All experimental animals developed large, heterogeneous brain tumors that closely resembled human GBM. Median survival was 92 days from tumor initiation and 62 days from the first point of tumor visualization on MRI. Each tumor-bearing animal showed time dependent evidence of malignant progression to high-grade glioma by MRI and neurological examination. Post-mortem tumor analysis demonstrated the presence of several key characteristics of human GBM, including high levels of tumor cell proliferation, pseudopalisading necrosis, microvascular proliferation, invasion of tumor cells into surrounding tissues, peri-tumoral reactive astrogliosis, lymphocyte infiltration, presence of numerous tumor-associated microglia- and bone marrow-derived macrophages, and the formation of stem-like cell niches within the tumor. This transgenic rat model may enable detailed interspecies comparisons of fundamental cancer pathways and clinically relevant experimental imaging procedures and interventions that are limited by the smaller size of the mouse brain.

Involvement of platelet‐derived growth factor ligands and receptors in tumorigenesis

“…not displaying the glioma-CpG island methylator phenotype) may be initiated by gain of chromosome 7 gain and loss of chromosome 10. By a computational model, PDGFA on chr 7 and PTEN on chr 10 RCAS-PDGFB Ntv-a mice wt, Ink4aÀ/À, ArfÀ/À, Ink4a-ArfÀ/À OG [379] RCAS-PDGFB Gtv-mice wt, Ink4aÀ/À, ArfÀ/À, Ink4a-ArfÀ/À OG [379] RCAS-PDGFB Gtv-mice ArfÀ/À OG [380] RCAS-PDGFB Ctv-a mice wt OG [186] RCAS-PDGFB Ctv-a mice, ArfÀ/À, Ink4a-ArfÀ/À OG [381] PDGFB-IRES-Cre retrovirus Pten fl/fl /Tp53 fl/fl mice GBM [199,382] Gfap/PDGFB/Tp53 null mice [187] PDGFB-IRES-GFP retrovirus Wt mice OG [383] RCAS-PDGFA Gtv-a, Ntv-a wt mice Low-grade OG [191] RCAS-PDGFA, RCAS-shp53 Wt mice High-grade OG [191] RCAS-PDGFA Pten or Cdkn2a null mice High-grade OG [191] PDGF-IRES-DsRed retrovirus Wt rats OG [189] RCAS/PDGFA, p53 shRNA Wt rats GBM [384] Nestin-Cre; Pdgfra V561D ; Ink4A/ArfÀ/À High-grade glioma [192] Nestin-Cre; Pdgfra D842V ; Ink4A/ArfÀ/À High-grade glioma [192] GFAP-Cre; Pdgfra V561D ; Ink4A/ArfÀ/À High-grade glioma [192] were found to be the critical genes [191]. Additional aberrations include inactivation of TP53 and CDKN2A.…”

Cross-species transcriptional analysis reveals conserved and host-specific neoplastic processes in mammalian glioma

“…Experimental mouse models examining combinations of PDGF-A overexpression with p53 deficiency, or combined p53, NF1, and PTEN deficiency in nestin-positive BTICs, have shown histopathologic and genetic similarity to the human proneural and mesenchymal tumor subtypes, respectively 8 – 10 , 14 . Similar tumors initiated in transgenic TV-A rats display many of the key features found in human tumors, such as microvascular proliferation and brain invasion 15 . This suite of genetically engineered RCAS/TV-A models enables the study of inter-species and tumor subtype-specific biological differences.…”

An in vivo multimodal feasibility study in a rat brain tumour model using flexible multinuclear MR and PET systems

“…Therefore, sophisticated methods for experimental and translational imaging in animal models are of great importance for the provision of a direct comparison to the results of histological and physiological parameters. Due to recent technical advancements in genetic engineering, tumour models with a specific genetic profile can now be generated which allow imaging methods to be tested for the non-invasive prediction of the corresponding genetic profile [27]. In this context, we have developed a stand-alone, simple multinuclear MR system for imaging animals at ultra-high field [28] that should be also capable of sequential acquisition with PET.…”