Fig. 1

GB cells upregulate TSPO expression upon contact with cytotoxic T cells and T cell-derived factors. a, b Western blot analysis shows TSPO protein expression in primary BTICs derived from 9 mesenchymal and 15 proneural GB subsets as well as GB cell lines U-87 MG and U-251 MG. a TSPO protein quantification of primary BTICs after actin protein normalization. b Blots used for the protein quantification indicated in (a). c Correlation between the expression of TSPO and CD3E, CD4, CD8A, GZMB, PRF1, and CD274 based on TCGA-GBM dataset. The analysis was performed by GEPIA web server [88]. R indicates Pearson`s correlation coefficient. (TPM: Transcripts per million) d-i Induction of TSPO expression in BTICs in response to cytotoxic T cells and T cell-derived factors. The primary cell lines BTIC13 (mesenchymal, d-f) and BTIC129 (proneural, g-i) were treated with supernatant of polyclonally activated FluTC or were co-cultured with FluTC at 1:1 ratio after being pulsed with diluting concentrations of flu-peptide (FluP). BTIC129 cells were additionally treated with supernatant of polyclonally activated TIL129. 20 h following treatment/co-culture, TSPO mRNA and protein expression in the remaining tumor cells were analyzed. d, g RT-qPCR analysis of TSPO mRNA expression in BTICs. Results are presented as fold change compared to the control medium (CM) condition after GAPDH mRNA normalization. e, f, h, i Western blot analysis of TSPO protein expression in BTICs. e, h Protein quantification is presented as fold change compared to the control medium (CM) condition after GAPDH protein normalization. f, i Representative blot of at least two independent experiments. d, g, h Cumulative data of three and (e) two independent experiments. Graphs represent mean ± SD. P-values were calculated using (a) Mann–Whitney test (d, g, h) two-tailed Student`s t-test (* = P < 0.05, ** = P < 0.01, *** = P < 0.005, **** = P < 0.001, ns: non-significant)