The bioinformatics analysis results found that CXCL9 was positively correlated with the traditional immune function checkpoint markers CTLA4, GZMB, LAG3, PDCD1, HAVCR2, etc., while further immunohistochemical experiments also confirmed that CXCL9 expression in clinical tissue specimens was significantly correlated with LAG3, PD1, PDL1, CTLA4, etc. This implies that CXCL9 might exert a crucial function in the immune response of breast cancer. Here, PDCD1 is linked to breast cancer.