The human tissue kallikreins (KLKs 1-3) and a novel KLK1 mRNA transcript are expressed in a renal cell carcinoma cDNA library.

Renal cell carcinoma (RCC) is the most common form of kidney cancer, for which there is no biochemical marker. We and others have previously shown that a prostate specific antigen (PSA)-like protein is elevated in the serum of women with RCC. PSA is a member of the tissue kallikrein (KLK) gene family of enzymes. We have constructed a RCC cDNA expression library and screened it for PSA and KLK expression to determine whether they may be responsible for this PSA-like activity. Since immunoscreening of the RCC library for expressed PSA-like proteins was unsuccessful, polymerase chain reaction (PCR) analysis of the RCC cDNA library was performed using universal KLK primers, directed to the common regions in exon 3 and exon 5 of KLK1, KLK2 and KLK3. Sequences identical to all three KLKs were present in the RCC cDNA library. In addition, a novel KLK1 transcript with a 104 base pair deletion in exon 4 that predicted a C terminal sequence minus the crucial Ser190, was detected. The role of these tissue kallikreins in RCC and the significance of the variant KLK1 transcript is yet to be established. It is still unclear which of these gene products, if any, was detected in the sera of the women with RCC.