The ABTC has provided unique expertise on brain tumor research in vitro and in vivo, despite the difficulties mentioned above. The following are some examples of the type of work the ABTC is involved in for generating preclinical data for potential translational trials: A. Evaluation of new cytotoxic, cytostatic, and radiation/chemotherapeutic sensitizing agents and neurotoxicity monitoring (80%). These screens consist of evaluating new agents in vitro against a number of different adult glioma, and primitive neuro-ectodermal cell lines. A significant number of anti-glioma agents have been screened and the selected agents are undergoing further testing in orthotopic brain tumor models using stereotactic technologies and evaluating a number of newer delivery technologies (besides standard oral or intravenous administration) including intracarotid administration, delivery with or without selective or gross blood-brain barrier disruption, convection delivery, etc. For example, the potential therapeutic effects of selective estrogen receptor modulators (SERMs) have been demonstrated in different human glioma cell lines and then confirmed by in vivo studies. Using the convection-enhanced drug delivery (CED) technique, various genetic vectors have been tested for delivering therapeutic agents to gliomas. Several new agents have been tested in vitro and in vivo, including full dose response curves and combinations with BCNU, a clinical anti-glioma drug. Furthermore, the ABTC has provided technical support to the investigators in NINDS-SNB for evaluating the role of stathmin in the resistance of malignant gliomas to DNA alkylating agents in vivo. Neurotoxicity has also been monitored by a routine animal screen. Having such a routine animal screen in place is a great incentive for the future development of neuroprotective agents through both academia and the pharmaceutical industry. B. Evaluation of novel endpoints (10%). As mentioned above, many of the new classes of anti-tumor therapeutics will have cytostatic rather than cytotoxic properties. Evaluating which of these agents will have biologic activity in humans in small, early clinical trials is a challenge since the standard response criteria are based on the determination of cytotoxic responses (i.e. the tumor shrinks by 50%). The only truly valid clinical parameter available for evaluating the activity of a truly cytostatic agent is patient survival or tumor progression-free survival. These, however, are not useful parameters for screening drug activity in small, early phase clinical trials. Thus, if surrogate markers of biologic activity could be identified, one could utilize these as early endpoints for screening out agents with little or no activity in vivo. Toward that end, the ABTC will actively develop surrogate markers of anti-tumor drug activity that can be utilized and validated in clinical trials, which includes three major areas: 1) Imaging; 2) Gene Expression Profiling; 3) Proteinomics. In collaboration with investigators in NOB, NCI and NINDS, noninvasive MR imaging has been used for magnetically labeled stem cells to directly identify neovasculature in a glioma model. C. Brain tumor repository of mouse models and cell lines (10%).A number of mouse brain tumor models have been generated, as have human brain tumor cell lines. These reagents have been generally constructed in individual laboratories, and there currently is no central place to acquire such reagents. Thus, it is our intention to collect these reagents from our collaborators throughout the country (particularly through brain tumor efforts in the Mouse Models of Human Cancer Consortia) and characterize these tumors and cell lines, morphologically, cytogenetically, immunohistochemically, and genetically through expression profiling. We will utilize the most appropriate of these models for our preclinical evaluations. At least 8 human and 3 rat glioma cell lines that are commercially available have been stocked and used by the ABTC. In addition, we have collected many clinical glioma specimens and established low-passage primary glioma cultures for evaluation of new anti-cancer drugs or for study of gliomagenesis in vitro and in vivo. The major mission of the NOB Animal Brain Tumor Core is to provide services for the investigators to evaluate potential anti-glioma agents in vitro and in vivo. In addition to coordinating animal studies with investigators, ACUC, and NCI animal facility/animal care personnel, the ABTC provides technical support in establishment of glioma models (both intracranial and subcutaneous), drug administration, clinical observation, and primary pathological services. A significant amount of anti-cancer drugs have been tested in vitro and in vivo (Anti-TRAIL Receptor antibodies, SERMs, LY317615, ATNs). For example, the selective estrogen receptor modulators (SERMs) have been screened on different human glioma cell lines to evaluate their potential therapeutic effects. The in vivo study has also demonstrated their therapeutic effects: The mice that received SERM treatment showed longer survival time vs. controls, which could be prolonged further, when delivered by a convection-enhanced drug delivery (CED) technique. Using the CED technique, anti-TRAIL Receptor antibodies and Adeno-Associated Viral (AAV) vectors have also been tested on intracranial human glioma nude rat models. Furthermore, the ABTC has also provided technical support to the investigators in CCR-NOB, CC-LDRR, and NINDS-SNB. One such project is to evaluate endothelial progenitor cells (EPCs) in glioma angiogenesis and imaging. In collaboration with the investigators in NCI and NINDS, we take advantage of the enormous small animal image facilities that are currently being constructed. Using the technology of high resolution MRI, MR spectroscopy, and PET scanning on small animals, we have the capabilities of quantitative microvasculature, vascular permeability, cerebral edema, and tumor metabolism. Previously, the investigators in NOB, NCI and NINDS identified a methodology for isolating and expanding in vitro a sub-population of human hematopoietic cells that are in fact endothelial progenitor cells (EPCs) and angioblasts. We have demonstrated that we can genetically engineer these cells ex-vivo to express marker genes or the thymidine kinase (TK) gene using retrovirus-mediated gene transfer. Genetically labeled EPCs were transplanted into immunocompromised mice and found to migrate and incorporate into the angiogenic vasculature of growing tumors while maintaining transgene expression. Ganciclovir (GCV) treatment resulted in tumor vascular collapse with resultant tumor necrosis in animals previously administered TK-expressing EPCs. Additionally, our EPC marker experiments have demonstrated that as much as 15-30% of tumor vasculature may in fact be bone marrow-derived, suggesting a paradigm shift in that tumor-associated neovasculature may not be derived just through angiogenic mechanisms as previously believed, but also through the embryonic process of vasculogenesis. Based on the previous finding, a collaborative study with LDRR for evaluation of Ferumoxides-Protamine Sulfate (FE-PRO) complex for labeling EPCs in established intracranial glioma models by MRI is on-going. To [summary truncated at 7800 characters]
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