Intertumoral heterogeneity of immune infiltration in glioblastoma

• Applicant: Privatdozent Dr. Philipp Euskirchen
• Subject Area: Molecular and Cellular Neurology and Neuropathology ; Clinical Neurology; Neurosurgery and Neuroradiology
• Term: from 2016 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 310347880

Glioblastoma is the most frequent malignant primary brain tumor in adults. Despite multimodal therapy, patients face dismal prognosis with a median survival of 14.6 months. These tumors are infiltrated by immune cells, especially microglia, the sessile immune cells of the central nervious system. However, the extent of this immune infiltration is highly variable. The origins of this intertumoral cellular heterogeneity are currently unknown. Surprisingly, microglial cells secrete a number of factors that promote tumor growth. Thus, depletion of microglia is currently investigated as a novel therapeutic target in order to attenuate tumor cell proliferation. The overall goal of this proposal is to identify patient subgroups that benefit from a microglia targeted therapy.First, we aim to identify genotype-phenotype associations by histological correlation of microglial infiltration with tumor specific genetic alterations. Therefore, a well characterized cohort of histological samples of human glioblastoma (so called tissue microarray) is available. Our previous in silico work identified an influence of mutations in the IDH1 and NF1 genes which are frequently altered and considered pathogenetically relevant in glioblastoma. This correlation will first be verified histologically.Using NF1 mutations, that go along with increased microglial infiltration, as a proof of principle, we will then investigate their functional relevance using CRISPR-Cas9 mediated genome editing and a genetically well characterized library of glioma stem cell lines that have been generated by the participating laboratories and serve as in vitro and in vivo disease models. NF1-deficient and wildtype cell lines will be implanted orthotopically into the brains of nude mice and their growth patterns with respect to immune infiltration will be compared histologically to the matching parental tumors and tumor genotype. After rescue of NF1 mutation by CRISPR-Cas9 genetic engineering we hypothesize that there will be a reduction in infiltration by microglial cells and an impaired tumor growth. This will be followed up histologically and by MR imaging in vivo.Perspectively, we will be able to test the efficacy of microglia targeted therapeutics in disease models stratified for tumor genotype. These experiments, beyond the scope of the current proposal, are planned after returning to the home institution. Our goal is to foster the preclinical and early clinical investigation of new therapeutics by providing the means for a personalized cancer treatment.

• DFG Programme: Research Fellowships
• International Connection: France
• Hosts: Dr. Ahmed Idbaih; Professor Dr. Marc Sanson