Immunohistochemistry (IHC) staining and semi-quantitative scoring

IHC staining was conducted on the above sections according to the standardized procedures. Sections were retrieved by EDTA. The primary antibodies used were as follows: antiGBP2 (1:3000 dilution, Cat. 11854-1-AP, ProteinTech), antiPD-L1 (Ready-to-use, Cat. GT2280, GeneTech), antiPD-1 (Ready-to-use, Cat. GT2281, GeneTech), antiCD8 (Ready-to-use, Cat. GT2112, GeneTech), antiMLH1 (Ready-to-use, Cat. GT2304, GeneTech), antiMSH2 (Ready-to-use, Cat. GT2310, GeneTech), antiMSH6 (Ready-to-use, Cat. GT2195, GeneTech), and antiPMS2 (Ready-to-use, Cat. GT2149, GeneTech). Staining was visualized with DAB and hematoxylin counterstain, and stained sections were captured using Aperio Digital Pathology Slide Scanners. For semi-quantitative analysis, the stained sections were independently evaluated by two pathologists. GBP2 and PD-L1 were assessed by according to the evaluation standard on a 12-point scale by calculating the immunoreactivity score (IRS) [31]. CD8 and PD-1 were assessed by estimating the percentage of cells with strong intensity of membrane staining in the stromal cells.