Kallikreins are a subgroup of serine proteases and are implicated in carcinogenesis. A novel Kallikrein gene Prostase/KLK-L1 (also known as KLK4) is expressed and is up-regulated by androgens and progestins. KLK-L1 may be involved in the pathogenesis and/or progression of prostate, breast, and possibly other malignancies.