In particular, the RGS5+ cancer‐associated fibroblast cluster was identified and has been proven to negatively regulate the immune process in metastatic breast cancer by secreting periostin and biglycan.[22] We also confirmed that the level of CAF was negatively correlated with CD8+ effective T cell and NK cell level via bulk transcriptome analysis (Figure S7a, Supporting Information). The gene discussed is POSTN; the disease is cancer.