Radio-chemotherapy and metformin selectively modulate the heterogeneous landscape of glioma with ribosome biogenesis, long non coding RNA and immune-escape markers as major player

Glioblastoma multiforme (GBM) is the most common primary brain tumor in adults with a short survival time after standard therapy administration including radiotherapy (RT) associated with temozolomide (TMZ). Here, we investigated the effects of radiochemotherapy in association with metformin (MET), a drug targeting cell metabolism on a syngeneic GBM mouse model using Positron Emission Tomography imaging with [18F]FLT and [18F]VC701 and single-cell RNA-sequencing analysis. The addition of drugs to RT significantly increased survival and [18F]FLT showed an early predictive response of combined therapy. We identified the presence of heterogeneous tumor populations with different treatment sensitivity and a complex immune evasive microenvironment. Tumor cells surviving to treatments showed immune response, among the main differentially modulated biological functions and a potential role of long non-coding RNAs (lncRNAs) in treatment resistance. Association with TMZ or TMZ plus MET reduced the pro-tumor phenotype of immune reaction acting more on myeloid cells the first and on lymphocytes the latter. Off note, MET add-on counteracted the immune-evasive phenotype particularly of T cells suggesting a potential role of MET also in adopted immunity.