Harnessing DNA repair factors to promote an innate immune response against glioblastoma: an invitro RNAi screen selecting phagocytosis promoting genes in glioblastoma cells

CLINICAL CHALLENGESIN THE TREATMENT OF GLIOBLASTOMA: Glioblastoma (GBM) is the most frequent and aggressive primary tumor of the central nervous system (CNS). Despite surgery and radio-chemotherapy, tumor recurrence inevitably occurs as a result of therapy resistance driven by complex DNA repair mechanisms. Moreover, GBMs are defined as “immunologically cold” tumors that resist treatment with current immunotherapies. How to turn GBMs into "immunologically hot" tumors remains a considerable therapeutic challenge.In addition to promoting genetic stability and chemoresistance, DNA repair factors have emerged as crucial players in the mechanisms that govern anti-cancer immune responses, including the maturation and activation of macrophages in the tumor microenvironment, bringing new prospects for DNA repair based strategies in the fight against cancer.
HYPOTHESIS: Among non-neoplastic cells in the tumor microenvironment of GBM, the majority of cells are represented by tumor-associated microglia/macrophages (TAMs). Our observations have led us to consider that defective DNA repair in GBM cells may facilitate the mounting of an innate immune responseby macrophages. We hypothesize that targeting specific DNA repair factors in GBM may result in the release of damage-associated molecular pattern molecules (DAMPs), including nucleic acids, that will promote the development of an innate immune response mounted by macrophages.
OBJECTIVES AND SCIENTIFIC STRATEGY: Here, we plan to carry out a pilot project bringing together complementary expertise in DNA repair, innate immune response and GBM biology from the LIH, as well as partners from the University of Luxembourg and the Laboratoire National de Santé, in order to identify the key DNA repair factors representing relevant targets for an innate immune response against GBM. Specifically, we intend to demonstrate that RNA interference (RNAi) screening is a suitable approach for the identification and validation of such factors.To this end, we will use a siRNA library targeting DNA repair in an in vitro RNAi screen designed to monitor the phagocytosis of GBM cells by macrophages, inorder to identify phagocytosis-promoting factors in glioblastoma. Selected hits will be validated in vitro and characterized using clinical GBM biopsies.
EXPECTED RESULTS AND IMPACT: Lists of in vitro validated DNA repair factors will be proposed, providing proof-of-principle that targeting DNA repair is a realistic approach in the context of immunotherapeutic strategies against GBM and paving the way for strong intra-and inter-institutional collaboration in Luxembourg to elucidate the underlying mechanisms and design more efficient strategies against GBM, with the prospect of clinical application.