Table 1.

Studies examining PD-1/PD-L1 expression in prostate cancer.

Specimen Type	Number of Patients	Cut Off for Positivity	Antibody/Clone Used to Detect PD-L1	PD-L1 Expression
Primary prostate cancer [10]	402	No staining = 0, weak staining = 1, moderate staining = 2, and strong staining = 3. PD-L1+ stromal cells and PD-1+ lymphocytes were scored as number of positive stained cells per 0.6 mm diameter core as follows: 0 = 0–3, 1 = 4–10, 2 = 11–15, and 3 ≥ 15	Rabbit monoclonal PD-L1 antibody (Cat#13684, clone: E1L3N, Cell signaling technology, Danvers, MA, USA)	92% (371/402) of patients were positive for PD-L1 staining in tumor epithelial (TE) cells and 59% (236/402) had high PD-L1 intensity score. Also, 66% (267/402) of patients had PD-L1+ stromal cells.
Primary prostate cancer [11]	Training cohort (n = 209) Test cohort (n = 611)	Semi-quantitative scoring as negative (0), weak (1), moderate (2), or strong (3)	Monoclonal rabbit PD-L1 antibody (clone EPR1161)	Moderate to high PD-L1 levels in 52.2% in the training cohort and 61.7% in the test cohort
Primary prostate cancer [12]	20	>5% membrane staining of malignant epithelial cells	5H1 clone of the mouse anti-human CD274 monoclonal PD-L1 antibody	PD-L1 positivity in 15% (3/20) of samples
Primary prostate cancer [13]	16	PD-1 positivity: negative (0), <5%; low (1+), 5–30%; high (2+), >30% of CD3+ T cells. PD-L1 staining intensity: 0 (no signal), 1+ (light signal), 2+ (high signal) in >50% of neoplastic cells.	Clone 015, Sino biological	Eight of 16 (50%) were PD-L1 positive and 19% were strongly (2+) positive
Primary prostate cancer [14]	25	“High” expression- 3 to 5 on the semiquantitative 0 to 5 score. “Low” expression- 0 to 2 on the semiquantitative 0 to 5 score	Anti-PD-L1 clone 22C3; Merck research laboratories	Low: 92% (23/25) High: 8% (2/25)