CD274 and gastric cancer: While direct studies on microbiome and established biomarker (e.g., PD‐L1 expression, MSI status) interplay remain limited, insights can be extrapolated from related niches: Gut microbiome‐derived butyrate suppresses PD‐L1 and IL‐10 expression in tumor‐associated macrophages, thereby enhancing antitumor immunity in gastric cancer [32], and in lung cancer, higher diversity of the lung microbiome correlates with elevated PD‐L1 expression and improved response to anti‐PD‐1 therapy [33].