Fig. 6

TSPO regulates the expression of genes associated with apoptosis-resistance. a Principal component analysis (PCA) of RNA-Seq gene expression profiles from TSPO ± BTIC13. b Volcano Plot highlighting differentially expressed genes in TSPO-deficient BTIC13 (fold change ≥ 2, normalized counts per million > 2, false discovery rate (FDR) ≤ 0.05, labelled blue (downregulated) and red (upregulated)). c Heatmap of expression changes of DEGs associated with GO term: GOBP_REGULATION_OF_CELL_DEATH (GO:0010941) in TSPO ± BTIC13. Anti-apoptotic genes are indicated with a blue arrow. d Correlation between the expression of TSPO and CCDN2, B3GALT2, CEMIP, APOBEC3G, PI3, and SLPI at single-cell level [65]. R indicates Pearson`s correlation coefficient. e RT-qPCR analysis of PI3 and SLPI mRNA expression in control medium (CM) or TRAIL treated TSPO ± BTIC13. Results are presented as fold change compared to the CM condition of TSPO-proficient cells after β-actin mRNA normalization. f Luciferase-based caspase-3/-7 assay to measure caspase-3/-7 activation in PI3/SLPI downregulated BTIC13 upon 4 h co-culture with FluTC or treatment with 50 ng/ml TRAIL. g Real-time cytotoxicity assay to analyze TRAIL-induced caspase-3/-7 activation over 24 h in BTIC13 cells upon PI3 and SLPI double knockdown. The graphs show the total apoptotic tumor cell area (green object area) per well. h Western blot analysis of total/cleaved caspase-9/-3 and PARP1 in BTIC13 transfected with control or PI3-SLPI-specific siRNAs upon treatment with 50 ng/ml TRAIL. g, h Values represent the mean of triplicates ± SD. P-value was calculated using two-tailed Student`s t-test (* = P < 0.05, ** = P < 0.01, *** = P < 0.005, **** = P < 0.001)