Immunohistochemistry

Tissue microarrays were constructed as described previously.26 Immunohistochemical (IHC) staining was performed using mouse anti-human CD3 (Abcam, clone SP7), mouse anti-human CD8 (Dako, clone C8/144B), rabbit anti-human TIGIT (Abcam, clone BLR047F), and mouse anti-human CD56 (Dako, clone 123C3). TIL and IHC expression scores were determined by a blinded pathologist (MAD). TIL scores were calculated on H&E-stained slides as follows: 3 (>20 TIL/high-power field (hpf)), 2 (11–20 TIL/hpf), 1 (1–10 TIL/hpf), 0 (<1 TIL/hpf). IHC expression for CD3, CD8, CD56, and TIGIT was calculated as follows to derive an H-score: [1x (% 1+cells)+2x(% 2+cells)+3x(% 3+cells)] where 1+, 2+, and 3+ represent weak, moderate, and strong stain intensity, respectively. Final TIL and IHC expression scores were averaged when more than one consecutive section was present for scoring. PD-L1 staining of tumor samples was performed using a CLIA-certified laboratory.