P08.04 “The development tumor model” used to biologically and spatiotemporally follow and understand glioblastoma evolution in the whole brain and to test and monitor new therapies

To date, “The development tumor model” (TDTM) is the only preclinical animal model which can replicate the entire glioblastoma natural history both in the bulk and in the microinfiltrated brain parenchyma. Furthermore, the model is perfectly suited to testing new therapies and continuously monitor subclonal emerging populations after treatment in order to identify molecular predictors of response to innovative therapies. TDTM is a xenogeneic orthotopic transplantation model using glioblastoma-derived cell lines from the pre-hypoxic phase of the founding clone (or of the more ancestral one, inferred after reconstruction of the phylogenetic tree) cultivated in a neurobasal serum-free medium as transplanted material. The model posits the transplantation of the same number of cells into several genetically identical immunocompromised rodents (an inbred strain of mice or rats) at the same time (time zero). Thus, the model creates a pool of twin immunodeficient transplant animals examined under the same conditions. By sacrificing one animal a week (or choosing any time interval as needed) and obtaining multiple biopsies (from the bulk, ipsilateral hemisphere, corpus callosum, contralateral hemisphere) and stainings on sections during the progression of the xenograft, we can biologically and spatiotemporally (i.e geographically and longitudinally) reproduce and monitor both the entire evolution in the bulk (appreciating the evolving variegated clonal architecture and increasingly more complex intratumor heterogeneity) and detect all the steps, from the beginning to the end of the natural history, of brain parenchyma microinfiltration. The model, continuosly monitoring the progression of the brain parenchyma microinfiltration over the development of the glioblastoma xenograft, will enable us to sperimentally demonstrate the hypothesis (that many radiological, clinical, surgical clues and the genetic analysis of distant recurrences indicate) that the entire brain parenchyma microinfiltration happens in very early stages of glioblastoma development or likely even before the growth of the primary tumor bulk by the CSCs of the founding clone. Indeed, TDTM can enable us to identify the CSCs in the brain parenchyma shedding light on the perivascular parenchymal niche where founder CSCs have exited the cell-cycle and settle quiescent in G0 state until activation. Furthermore and fundamentally, TDTM is perfectly suitable to test novel therapies. By delivering to all rodents at the same time the identical dose and modality of therapeutic treatments over xenograft