The major mission of the PTRF is to provide services for clinical investigators to evaluate potential new anti glioma agents in vitro and in vivo. The NOB Lab has collaborated with pharmaceutical companies and academic institutions, and the NCI Developmental Therapeutics Program in the preclinical and clinical development of a number of new anti-glioma agents. The first step in the development pipeline is screening of the agent through the PTRF that provides the professional service for screening these agents both in vitro and in vivo using both standard subcutaneous and stereotactic intracranial models. Furthermore, PTRF provides experimental and technical support to other investigators both within and outside of the NOB for evaluating newly developed therapeutics. These extended studies involved stereotactic-based intracranial models looking at various dose and administration schedules as well as combination trials of the new drug with other agents. For example, the PTRF has helped to generate the RNA for gene expression profiles for given glioma cell lines treated with a specific class of agents. Once characteristic patterns are identified that correspond with anti tumor activity, then clinical trials can/will be devised to administer one of these agents to patients with brain tumors immediately prior to biopsy/surgery in order to attempt and identify a similar genetic profile clinically. In collaboration with the NOB Lab and the Genomic Core team, gene expression signatures are being generated in all of glioma cell lines and GIC/GSCs for all compounds tested within the PTRF. In addition, a number of newer drug delivery technologies including intra carotid administration, delivery with or without selective or gross blood-brain barrier disruption, convection delivery, etc. have been evaluated in animal models within the PTRF. 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. 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 clinical activity. Toward that end, the PTRF is actively working to develop surrogate markers of drug anti tumor activity that can be utilized and validated in clinical trials, which includes three major areas:1) Imaging; 2) Gene expression profiling; 3) Proteinomics/Serum markers. For example, in collaboration with investigators in NOB, NINDS and the Clinical Centers program of experimental imaging science, noninvasive MR imaging has been used to image magnetically labeled endothelial progenitor cells in vivo to directly identify vasculogenesis in a glioma model. Finally, the PTRF stores representative tumor, tissue and serum samples from animals treated with each new compound tested with the expectations that new candidate tissue and/or serum-based protein markers of drug activity, tumor activity and/or some tumor biological process (i.e. angiogenesis) may be found. This will be an invaluable preclinical resource for validating such claims in the future. A major effort of the NOB is to develop human glioma cell lines that more closely model primary human gliomas both biologically and molecularly. The PTRF is actively involved in the generation of primary human glioma cell lines and GIC/GSC lines from fresh surgical specimens for glioma patient operated on at the NIH. Working closely with the cancer stem cell biologists for the growth, propagation and characterization of each of these cell lines and animal xenografts, the PTRF uses these well-characterized cell lines as screens for two major categories of drugs; 1) The most promising drugs from the first levels of in vitro and in vivo screens using the more conventional established glioma cell lines; 2) The drugs that target pathways that may not be well represented by the biology of standard glioma cell lines but are reproduced in the GIC/GSCs. The laboratory expertise utilizing these cells, and the large resources of different GIC/GSC lines, are a potent enticement for potential partnerships between NCI and the pharmaceutical/ biotechnology community given their growing appreciation of the limitation of standard cancer cell lines and the promise of cancer stem cells for better representing the human disease. Since the PTRF was initiated in 2016, four clinical trials have activated as a direct result of translational work performed within the NOB, all of which had preclinical animal studies performed within the facility. Furthermore, we have identified 3 compounds solely through the preclinical screening program that have since been brought forward to clinical trials at the NIH (Regadenoson, TG02, LB100). PTRF is further extending the translational studies, such as experimental immunotherapeutics and metabolic targeting therapeutics, as well as the experimental therapeutics for rare CNS tumors (Animal Study Proposal: NOB005, 006, and 008).
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