Differential splicing of KLK5 and KLK7 in epithelial ovarian cancer produces novel variants with potential as cancer biomarkers.

PURPOSE: The wild-type or variant mRNAs of several kallikrein (KLK) genes, such as KLK4, are highly expressed in ovarian carcinomas and may have potential as tumor markers. Two of these KLK genes (KLK5 and KLK7) and their proteins (hK5 and hK7) were first identified in the skin epidermis, where hK5 may be the physiological activator of hK7. The purpose of this study was to reexamine the expression of KLK5/hK5 and KLK7/hK7 and their association and to determine whether cancer-related variant transcripts were expressed. EXPERIMENTAL DESIGN: The expression of KLK5/hK5 and KLK7/hK7 was analyzed in the same cohort (n = 37) of benign (n = 4) and malignant ovarian tissue (n = 23) samples and primary cultured cells (n = 21) and in 8 ovarian cancer cell lines using semiquantitative RT-PCR; Southern, Northern, and Western blot analyses; and immunohistochemistry techniques. RESULTS: We showed the concordant higher expression of both KLK5/hK5 and KLK7/hK7 in ovarian carcinomas, especially late-stage serous carcinomas, compared with normal ovaries and benign adenomas. We also found that one novel KLK5 transcript with a short 5'-untranslated region and a novel KLK7 transcript with a long 3'-untranslated region were highly expressed in the ovarian cancer cell lines OVCAR-3 and PEO1, respectively, but were expressed at very low levels in normal ovarian epithelial cells. Both Western blot and immunohistochemistry analyses showed that these two enzymes are secreted from ovarian carcinoma cells. CONCLUSIONS: Our study demonstrated that hK5 and hK7, or more specifically, the short KLK5 and long KLK7 transcripts, may be useful as tumor markers for epithelial-derived serous carcinomas. However, additional clinical studies assessing serum levels of these putative biomarkers are required to confirm their usefulness in the diagnosis and/or monitoring of these tumors.

A novel transcript from the KLKP1 gene is androgen regulated, down-regulated during prostate cancer progression and encodes the first non-serine protease identified from the human kallikrein gene locus.

BACKGROUND: The kallikrein-related (KLK) serine protease, prostate specific antigen is the current marker for prostate cancer (PCa). Other members of the KLK family are also emerging as potential adjunct biomarkers for this disease. Our aim was to identify and characterize novel KLK-related genes with potential as PCa bio-markers. METHODS: Low stringency DNA screening was coupled with amplification techniques to identify novel sequences. Transcripts were examined by Northern blot, RT-PCR, and in situ hybridization analysis and in silico bioinformatics approaches. Protein characterization was performed by Western blot and confocal microscopy analysis. Gene regulation studies were performed by quantitative PCR and promoter reporter assays. RESULTS: We identified a novel kallikrein-related mRNA designated KRIP1 (kallikrein-related, expressed in prostate 1) which, together with the recently reported PsiKLK1 and KLK31P transcripts, is transcribed from KLKP1; a gene evolved from, and located within, the KLK locus. Significantly, in contrast to these other non-coding KLKP1 transcripts, the KRIP1 mRNA generates an approximately 18 kDa intracellular protein-the first non-serine protease identified from the KLK locus. KRIP1 mRNA is abundant only in normal prostate and is restricted to cells of epithelial origin in normal and diseased glands. Ligand binding of the androgen receptor increases transcription from the KLKP1 gene. Consistently, KRIP1 mRNA levels are lower in PCa samples compared to benign prostatic hyperplasia. CONCLUSIONS: Transcription from KLKP1 is reduced as cells de-differentiate on the pathway to malignancy. KLKP1/KRIP1 has potential as a marker of both PCa progression and recent evolutionary events within the KLK locus.