Steroid hormones were also reported to play a role in the expression of S100P, including the synthetic androgen R1881, which regulates the expression of S100P in prostate cancer [46], as well as P4 and six other types of clinically relevant synthetic progestins, which up-regulate S100P in progesterone receptor (PR)-positive cell lines of breast cancer [47]. This evidence concerns the gene S100P and breast cancer.