Fig. 5: GDF-15 expression is negatively correlated with intratumoral T cell infiltration in brain metastases from melanoma patients and in HPV⁺ oropharyngeal squamous cell carcinomas.

a–d Formalin-fixed paraffin-embedded tissues from melanoma brain metastases from 70 patients were stained by immunohistochemistry for GDF-15 and for the T cell marker proteins CD3 and CD8. Exemplary stainings are shown in a. b–d For hGDF-15 expression, a score was based on frequency (0–1% → score 0; 1–10% → score 1; 10–25% → score 2; 25–50% → score 3; >50% → score 4) multiplied with staining intensity (weak → 1, moderate → 2, strong → 3)). e–h GDF-15 serum levels were assessed from patients with human papilloma virus (HPV)⁺ or HPV^- oropharyngeal squamous cell carcinomas (OPSCC). Tumor-infiltrating CD8⁺ T cells per area were quantitated for 37 HPV⁺ tumors and correlated with the corresponding GDF-15 serum levels (e). f–h GDF-15 serum levels were divided into two groups with either GDF-15 < 1.0 ng/ml or GDF-15 ≥ 1.0 ng/ml. Kaplan–Meier plots for disease-specific survival were plotted for these two groups for patients with OPSCC irrespective of HPV status (n = 86) (f), as well as for HPV^- (n = 32) (g) and HPV⁺(n = 54) (h) OPSCC. Spearman´s rank-correlation coefficients (ρ) and p-values are indicated for b–e. Dotted trend lines were added for visualization. Kaplan–Meier curves were compared by log-rank (Mantel-Cox) test (f–h). Source data for b–h are provided as a Source Data file.