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.
Kaushal
Aneel
A
Institute of Health and Biomedical Innovation, Queensland University of Technology, Kelvin Grove, Australia.
Myers
Stephen A
SA
Dong
Ying
Y
Lai
John
J
Tan
Olivia L
OL
Bui
Loan T
LT
Hunt
Melanie L
ML
Digby
Matthew R
MR
Samaratunga
Hemamali
H
Gardiner
Robert A
RA
Clements
Judith A
JA
Hooper
John D
JD
D000595:Amino Acid Sequence; D000728:Androgens / Q000235:genetics*; D001483:Base Sequence; D014408:Biomarkers, Tumor; D045744:Cell Line, Tumor; D015536:Down-Regulation; D019143:Evolution, Molecular; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D010447:Peptide Hydrolases / Q000235:genetics; D011467:Prostate / Q000502:physiology; D011470:Prostatic Hyperplasia / Q000235:genetics / Q000473:pathology / Q000503:physiopathology; D011471:Prostatic Neoplasms / Q000235:genetics* / Q000473:pathology / Q000503:physiopathology; D012333:RNA, Messenger / Q000378:metabolism; D020840:Tissue Kallikreins / Q000235:genetics*; D014158:Transcription, Genetic
D000728:Androgens; D014408:Biomarkers, Tumor; C511310:KLKP1 protein, human; D012333:RNA, Messenger; D010447:Peptide Hydrolases; D020840:Tissue Kallikreins