NEURO-IMMUNE INTERACTIONS IN GLIOBLASTOMA CONTEXT: A NEW ROUTE?

Glioblastoma (GBM) is a grade IV glioma with the highest frequency and lethality among primary brain cancers in adults and the best treatment provides a median survival of 15 months. Unraveling the complex biology of GBM could open routes for new and needed therapies for this disease. Therefore, it is necessary to investigate not only the biology of the tumor itself but also its microenvironment and the initiation and maintenance of the immune response against the tumor. The study of the α7 subunit of nicotinic acetylcholine receptors (α7nAChR) has the potential to meet this need. Since the literature provides evidence that supports the hypothesis that α7nAChR may be involved with pro-tumor and immunosuppressive phenomena. MATERIAL AND METHOD Monocyte-derived dendritic cells (mo-DCs) were stimulated with TNF-α and subsequently exposed to acetylcholine (ACh) 1, 25 or 100µM, Methyllycaconitine (MLA) - specific competitive antagonist of α7nAChR - 25µM, ACh+MLA, 100µM ACh + 25 or 50µM MLA and vehicle, the expression of molecules C80, CD83, CD86, CD40, CCR7, and PD-L1 were analyzed in a flow cytometer. Flow cytometry was also used for analyzed the endocytic capacity and the expression of CD206 by immature mo-DCs. The mitochondrial viability of human GBM cells (U87MG) exposed to the same treatments was evaluated by MTT. RESULTS AND CONCLUSION Only ACh treatments were able to produce a trend (*p=0.0625) of reduction in the expression of co-stimulatory molecules CD80 [25 µM] and CD83 and [100 µM], CD40 [1 µM], and the co-inhibitor molecule CD274 [1 and 25µM]. The ratio between the expression of the CD274 molecule by the expression of co-stimulatory molecules was qualitatively higher in an ACh-mediated and “concentration-dependent” manner. The groups treated with MLA, simultaneously or not with ACh, presented ratio values between CD274 and co-stimulatory molecules very close to each other and especially for the CD274/CD40 ratio close to of vehicle value. Qualitatively the treatment of immature mo-DCs with ACh reduced the endocytic activity [1 and 25 µM], but without altering the expression of CD206. On the other hand, the group treated with MLA presented an expression index of CD206 approximately 32% lower in relation to the control index. The GBM cells exposed to 10μM of ACh + 20μM of MLA (1:2) exhibited the greatest reduction in viability compared to the control group, approximately 37%. Using bioinformatics web tools, expression of α7nAChR in GBM tumor cells is not a predictor of survival. Despite this, the α7nAChR in GBM cells positively correlates with the expression of some molecules known to be involved in tumor genesis, progression and/or recurrence, for example: TGFβI (p=1e-09,R=0.46), HIF-1α (p=1e-05,R=0.33), VEGFR (p=2.5e-04,R=0.28), PIK3CB (p=0,028,R=0.17) and PDGFR (p=0,042,R=0.16). Expanding these results could open the way for the exploration of α7nAChR as a therapeutic target adjuvant to immunotherapy or other treatment approaches for GBM.