Identification and molecular characterization of five novel kallikrein gene 13 (KLK13; KLK-L4) splice variants: differential expression in the human testis and testicular cancer.

The kallikrein gene family is comprised of genes that have either established or potential applications in prostate and breast cancer diagnostics. New members of the human kallikrein gene family have been recently identified. By using the positional candidate gene approach, we were able to clone a novel human serine protease gene that maps to chromosome 19q13.3-q13.4, the location of the kallikrein gene family. We named this gene KLK-L4 (now also known as KLK13). Here, we describe the identification of five new KLK-L4 splice variants which are not expressed in any other tissue except the human testis. We have further established that these splice variants can be detected in normal testis but not in the adjacent matched testicular tumors. In addition, differential expression of the KLK-L4 gene was found in various histological types of testicular cancer. Our results suggest that the KLK-L4 gene is expressed in normal and cancerous testicular tissue; however, its five variants are all expressed in normal tissue but not in testicular tumors. The physiological relevance of these variants and the implications of their differential expression between cancerous and normal tissues are currently unknown.