CCND1 and breast cancer: TFF1 belongs to the trefoil factor family, which plays an important role in various types of physiological activities in the body; normally, it is less expressed in the mammary gland, and in case of overexpression, it will cause female estrogen imbalance and at the same time increase cyclin D1 and accelerate the proliferation of breast tissue cells [24] and eventually induce breast cancer.