Tumor cell and immune cell profiles in primary human glioblastoma: Impact on patient outcome

The distribution and role of tumor-infiltrating leucocytes in glioblastoma (GBM) remain largely unknown. Here, we investigated the cellular composition of 55 primary (adult) GBM samples by flow cytometry and correlated the tumor immune profile with patient features at diagnosis and outcome. GBM single-cell suspensions were stained at diagnosis (n = 44) and recurrence following radiotherapy and chemotherapy (n = 11) with a panel of 8-color monoclonal antibody combinations for the identification and enumeration of (GFAP(+)CD45(-)) tumor and normal astrocytic cells, infiltrating myeloid cells -i.e. microglial and blood-derived tumor-associated macrophages (TAM), M1-like, and M2-like TAM, neutrophils. and myeloid-derived suppressor cells (MDSC)- and tumor-infiltrating lymphocytes (TIL) -i.e. CD3(+)T-cells and their TCD4(+), TCD8(+), TCD4(-)CD8(-), and (CD25(+)CD127(lo)) regulatory (T-regs) subsets, (CD19(+)CD20(+)) B-cells, and (CD16(+)) NK-cells-. Overall, GBM samples consisted of a major population (mean +/- 1SD) of tumor and normal astrocytic cells (73% +/- 16%) together with a significant but variable fraction of immune cells (24% +/- 18%). Within myeloid cells, TAM predominated (13% +/- 12%) including both microglial cells (10% +/- 11%) and blood-derived macrophages (3% +/- 5%), in addition to a smaller proportion of neutrophils (5% +/- 9%) and MDSC (4% +/- 8%). Lymphocytes were less represented and mostly included TCD4(+) (0.5% +/- 0.7%) and TCD8(+) cells (0.6% +/- 0.7%), together with lower numbers of TCD4(-)CD8(-) T-cells (0.2% +/- 0.4%), T-regs (0.1% +/- 0.2%), B-lymphocytes (0.1% +/- 0.2%) and NK-cells (0.05% +/- 0.05%). Overall, three distinct immune profiles were identified: cases with a minor fraction of leucocytes, tumors with a predominance of TAM and neutrophils, and cases with mixed infiltration by TAM, neutrophils, and T-lymphocytes. Untreated GBM patients with mixed myeloid and lymphoid immune infiltrates showed a significantly shorter patient overall survival versus the other two groups, in the absence of gains of the EGFR gene (p = 0.02). Here we show that immune cell infiltrates are systematically present in GBM, with highly variable levels and immune profiles. Patients with mixed myeloid and T-lymphoid infiltrates showed a worse outcome.

Automated summary

This study investigated the cellular composition of 55 GBM samples and correlated the tumor immune profile with patient features and outcomes. The GBM samples primarily consisted of tumor and normal astrocytic cells, along with a significant but variable fraction of immune cells. Three distinct immune profiles were identified in the GBM samples, with untreated patients showing worse outcomes when immune infiltrates included a mixed population of myeloid and T-lymphoid cells.