Prostase/KLK-L1 is a new member of the human kallikrein gene family, is expressed in prostate and breast tissues, and is hormonally regulated

By using the positional candidate gene approach, we were able to identify a novel serine protease gene that maps to chromosome 19q13.3-q13.4. Screenin g of expressed sequence tags allowed us to establish the expression of the gene and delineate its genomic organization (GenBank accession no. AF135023 ). We named this gene KLK-L1. Another group, by using a subtraction hybridi zation method, cloned the same gene and named it prostase (GenBank accessio n nos. AF113140 and AF113141). Here, we describe the precise mapping and lo calization of the prostase/KLk-L1 gene between the known genes KLK2 (human glandular kallikrein) and zyme (also known as protease M/neurosin). The dir ection of transcription of prostase/KLK-L1 is the same as that of zyme but opposite to that of KLK2 and prostate-specific antigen genes. Contrary to t he initial impression, prostase/LK-L1 is expressed at high levels not only in prostate tissue but also in testis, mammary gland, adrenals, uterus, thy roid, and salivary glands. We have further demonstrated with in vitro exper iments with the breast carcinoma cell line BT-474 that this gene is express ed and that its expression is up-regulated by androgens and progestins. On the basis of information on other genes that are localized in the same regi on (prostate-specific antigen, KLK2, zyme, and normal epithelial cell speci fic-1 gene), we speculate that prostase/KLK-L1 may be involved in the patho genesis and/or progression of prostate, breast, and possibly other malignan cies.