Immunohistochemical Staining and Scoring of CD8 and PD-L1

Immunohistochemical (IHC) staining and scoring of CD8 were the same as in our previous research.^{52 (link)} In detail, we spliced formalin-fixed, paraffin-embedded tumor tissues into 4 mm slides for IHC staining with CD8 antibody (1:50, ZSGB Bio, catalog No: ZA-0508) using an automated Leica Bond staining system according to the manufacturer’s protocol. The PD-L1 IHC staining procedure was performed with the PD-L1 IHC 22C3 pharmDx (Dako, Inc.) companion diagnostic test on the Dako Autostainer Link 48 platform. For scoring the IHC image, Histoscore (H-score) was calculated by multiplying the proportion of positive cells in the sample (0–100%) by the average intensity of the positive staining (1+, 2+, or 3+) to obtain a score ranging between 0 and 300 as previously described.^{70 (link)}