High density of S100A9 positive inflammatory cells in prostate cancer stroma is associated with poor outcome

Abstract Purpose To elucidate if the density of inflammatory cells expressing S100A9 in malignant and surrounding non-malignant prostate tissues is a prognostic marker for outcome in prostate cancer patients. Experimental design Tissue was obtained from 358 men diagnosed with prostate cancer at transurethral resection of the prostate due to obstructive voiding problems, of which 260 were then followed with watchful waiting. Tissue microarrays of both malignant and non-malignant tissues were stained with an antibody against S100A9. The number of stained inflammatory cells was scored and related to clinical outcome and histopathological parameters of known prognostic value. Results A high number of inflammatory cells expressing S100A9 in both malignant and surrounding non-malignant tissues were associated with significantly shorter cancer-specific survival. This association remained significant when Gleason score and local tumour stage were analysed together with S100A9 in a Cox regression model. Low number of S100A9 positive cells in non-malignant stroma was correlated to significantly longer cancer-specific survival also in patients with Gleason score 8–10 tumours. S100A9 positive cells in tumour stroma were correlated with Gleason score, hyaluronan, platelet-derived growth factor receptor beta (PDGFR-β), and androgen receptor (inverse correlation) in tumour stroma. S100A9 positive cells in non-malignant stroma correlated with androgen receptor in this tissue compartment (inverse correlation). Conclusions A high number of S100A9 positive inflammatory cells in tumour stroma and in non-malignant stroma were associated with shorter cancer-specific survival in prostate cancer patients.