Trop2 involves in promoting cell proliferation, inhibiting cell apoptosis, and regulating transcription factors via the MAPK pathway, β-catenin pathway, etc. Trop2 is overexpressed in about 62.4% of breast cancers and was especially overexpressed in TNBC at a rate of 78.1% [51]. This evidence concerns the gene TACSTD2 and breast cancer.