CTSB and cancer: Among them, SPP1+ macrophages are a common subset that participates in tumor angiogenesis through interaction with SPP1‐CD44 of adjacent cancer‐associated fibroblasts (CAFs); these cells are related to the epithelial‐mesenchymal transformation (EMT) and poor prognosis of cancer patients.[29] Additionally, APOE+ macrophages, CTSB+ macrophages, FOLR2+ macrophages, and S100A9+ macrophages accounted for the largest proportion of non‐responders, with the first three having the highest M.Sig.Score.