Immune cells subpopulations in peripheral blood in patients with glioblastoma

Background - High-grade gliomas (HGG) are the deadliest type of primary brain tumors. Tumor microenvironment characterization may provide new insights in understanding disease and the balance between inflammatory and suppressor cells and represent a key factor in tumor-microenvironment interaction. This study aims at characterizing peripheral immune cells subpopulations in HGG patients. Materials & Methods - We analyzed peripheral blood mononuclear cells (PBMC) from 57 patients with newly diagnosed HGG who underwent surgery in Neurosurgery department from 2019 to 2023. Blood sample was taken before surgery and PBMC were stored in Institutional Biobank. Clinical and radiological features and steroid dosage at sample time were recorded. For flow cytometry analysis, two panels of antibodies were designed, one for myeloid and one for lymphoid cells. Acquisition was performed with BC CytoFLEX LX and CytExpert software and data were processed with FCS Express 7. Statistical analysis was performed with SPSS 28. Results - Survival data were available for 52 patients: the mean overall survival (OS) was 15.98 months. A Cox regression analysis was performed to identify any prognostic impact of subpopulations, on which steroids’ influence was checked. A small effect was noted for monocytes (HR 1.055, p 0.018) and CD11b+/CD33+ cells including peripheral myeloid-derived suppressor cells (MDSC, HR 1.044 , p 0.055), both influenced by steroids. A stronger effect was noted for immature NK cells (HR 0.198, p 0.029), uninfluenced by steroids. A significant correlation was found between immature NK cells and ECOG performance status (PS), with higher levels in patients with lower ECOG (p 0.029). MDSC and CD8+ T cells were more represented in patients with necrosis on MRI while patients with midline shift showed higher MDSC and lower immature NK cells. FLAIR volume was positively correlated with mature NK while MDSC and mature NK showed a correlation near to significance with the difference between FLAIR and contrast-enhancing volume. Conclusions - These results are promising in identifying subpopulations in peripheral blood with a putative role in patients’ OS. Higher immature NK cells correlate with higher PS at surgery and are associated with increased OS. On the other hand, monocytes and MDSC correlate with radiological parameters such as midline shift, necrosis, and FLAIR volume. Further analysis on larger sample and longer follow-up is required to confirm these results.