The prognostic role of immune checkpoint markers programmed cell death protein 1 (PD-1) and programmed death ligand 1 (PD-L1) in a large, multicenter prostate cancer cohort

Abstract

Programmed cell death protein 1 (PD-1) and its ligand Programmed death ligand 1 (PD-L1) have gained massive attention in cancer research due to recent availability and their targeted antitumor effects. Their role in prostate cancer is still undetermined. We constructed tissue microarrays from prostatectomy specimens from 535 prostate cancer patients. Following validation of antibodies, immunohistochemistry was used to evaluate the expression of PD-1 in lymphocytes and PD-L1 in epithelial and stromal cells of primary tumors. PD-L1 expression was commonly seen in tumor epithelial cells (92% of cases). Univariate survival analysis revealed a positive association between a high density of PD-1+ lymphocytes and worse clinical failure-free survival, limited to a trend (p = 0.084). In subgroups known to indicate unfavorable prostate cancer prognosis (Gleason grade 9, age < 65, preoperative PSA > 10, pT3) patients with high density of PD-1+ lymphocytes had a significantly higher risk of clinical failure (p = < 0.001, p = 0.025, p = 0.039 and p = 0.011, respectively). In the multivariate analysis, high density of PD-1+ lymphocytes was a significant negative independent prognostic factor for clinical failure-free survival (HR = 2.48, CI 95% 1.12-5.48, p = 0.025).

Keywords: PD-1; PDL-1; immunohistochemistry; prognostic marker; prostate cancer.

Figure 1. Immunohistochemical analysis

(A) Low density PD-L1+ stromal cells, (B) High density PD-L1+ stromal cells, (C) Low intensity PD-L1+ tumor epithelial cells, (D) High intensity PD-L1+ tumor epithelial cells, (E) Negative isotype control antibody for PD-L1 (prostate TMA), (F) Negative control for PD-L1 (brain), (G) Positive control for PD-L1 (placenta), (H) Low density of intratumoral PD-1+ lymphocytes, (I) High density of intratumoral PD-1+ lymphocytes, (J) PD-1 and CD8 double stain with pink showing PD-1 positivity, and brown showing CD8 positivity, (K) Negative isotype control antibody for PD-1, (L) Negative control for PD-1 (brain), (M) Positive control for PD-1 (tonsil), (N) Positive control for PD-1 and CD8 double stain (tonsil). Magnification ×400 for all, except (N) which shows ×50 magnification.

Figure 2. Biochemical failure-free survival curves for PD-L1 intensity in tumor epithelial cells

Grey lines indicate low intensity, whereas black lines indicate high intensity.

Figure 3. Clinical failure-free survival curves for PD-1+ lymphocytes in tumor stromal areas

Grey lines indicate low density, whereas black lines indicate high density. (A) All patients, (B) Patients with age < 65, (C) Patients with pTstage = 3, (D) Patients with preoperative PSA > 10, (E) Patients with Gleason grade = 9.