POSTN and breast cancer: In the perivascular niche, sustained dormancy of breast cancer cells can be induced by thrombospondin-1 secreted from endothelial cells.115 Additionally, the endothelium-derived vasculature has been demonstrated to epigenetically trigger dormancy in metastatic tumor cells through Wnt factor secretion.116 However, as breast cancer progresses, neovessels originating from endothelial cells become enriched with tumor-promoting factors such as TGF-β1 and periostin, which subsequently drive the proliferation and metastasis of breast cancer cells.115