TFF1 and breast cancer: For example, trefoil factor 1 (TFF1), a small cysteine-rich protein that is frequently expressed in breast tumors under estrogen control treatment, is highly related to the migration of breast cancer cell lines;38,39 trefoil factor 3 (TFF3) is a predictive biomarker of endocrine response in breast cancer40 and is associated with breast cancer phenotypes.41