FOXP1 and esophageal squamous cell carcinoma: Proteomic mapping of SEC22B interactors revealed FOXP1, a transcriptional regulator with predicted PD-L1 promoter affinity (JASPAR score >0.85) (Figure S5E), exhibiting significant co-expression in ESCC cohorts (GEPIA: R=0.52, p=7.3e-15, Figure S5F).