Immune infiltrates and PD-L1 expression in treatment-naïve acinar prostatic adenocarcinoma: an exploratory analysis.

Tumour-induced immunosuppression plays a role in the development and progression of cancer. Of interest is the interaction between programmed death-1 and programmed death ligand-1 (PD-L1) which can be targeted through immune checkpoint blockade; however, there are limited data surrounding the composition of the immune milieu in prostate cancer. We preliminarily assessed 21 radical prostatectomies in therapy-naïve patients for immune markers and PD-L1 expression. The immune infiltrates were higher in adenocarcinoma than benign prostate (lymphocytes p<0.001, macrophages p=0.010) with 5% of cases being PD-L1 high (≥5% expression). Increased peritumoural CD68 and CD163 expression correlated with lower grade group (GG) (p=0.024 and p=0.014, respectively) with a trend towards increased CD68 expression in lower stage cases (p=0.086). There was also increased CD45 expression in lower GGs (p=0.063). We found the immune infiltrate in acinar prostate cancer to be extremely heterogeneous with an overall immunophenotype unlikely to respond to immune checkpoint blockade.

Journal of clinical pathology. 2018 Sep 26 [Epub ahead of print]

Elan Hahn, Stanley K Liu, Danny Vesprini, Bin Xu, Michelle R Downes

Anatomic Pathology, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada., Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre and University of Toronto, Toronto, Ontario, Canada., Anatomic Pathology, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada .