Characterization of the prostate cancer susceptibility gene KLF6 in human and mouse prostate cancers.
BACKGROUND
Krüppel-like factor (KLF) 6 is a candidate tumor suppressor gene in prostate cancer, but the mechanisms contributing to its loss of expression are poorly understood. We characterized KLF6 expression and DNA methylation status during prostate tumorigenesis in humans and mice.


METHODS
KLF6 expression was assessed in matched human non-malignant (NM) and tumor prostate tissues (n = 22) by quantitative real-time PCR (qPCR) and in three independent human prostate cancer cohorts bioinformatically. QPCR for KLF6 expression and methylation-sensitive PCR (MSP) were performed in human prostate LNCaP cancer cells after 5-aza-2'-deoxycytidine treatment. Klf6 protein levels and DNA promoter methylation were assessed in TRansgenic Adenocarcinoma of Mouse Prostate (TRAMP) tumors by immunohistochemistry and MSP, respectively.


RESULTS
KLF6 splice variants expression was increased (P = 0.0015) in human prostate tumors compared to NM tissues. Overall, KLF6 was decreased in metastatic compared to primary prostate cancers and reduced expression in primary tumors was associated with a shorter time to relapse (P = 0.0028). Treatment with the demethylating agent 5-aza-2'-deoxycytidine resulted in up-regulation of KLF6 expression (two-fold; P = 0.002) and a decrease in DNA methylation of the KLF6 promoter in LNCaP cells. Klf6 protein levels significantly decreased with progression in the TRAMP model of prostate cancer (P < 0.05), but there was no difference in Klf6 promoter methylation.


CONCLUSIONS
KLF6 expression was decreased in both clinical prostate cancer and the TRAMP model with disease progression, but this could not be explained by DNA methylation of the KLF6 promoter.
Dame Roma Mitchell Cancer Research Laboratories and Adelaide Prostate Cancer Research Centre, Discipline of Medicine, The University of Adelaide and Hanson Institute, Adelaide, Australia.
Karen
K
Chiam
Natalie K
NK
Ryan
Carmela
C
Ricciardelli
Tanya K
TK
Day
Grant
G
Buchanan
Aleksandra M
AM
Ochnik
Krisna
K
Murti
Luke A
LA
Selth
Lisa M
LM
Butler
Wayne D
WD
Tilley
Tina
T
Bianco-Miotto
D000818:Animals; D045744:Cell Line, Tumor; D015331:Cohort Studies; D018450:Disease Progression; D015536:Down-Regulation / Q000235:genetics; D020022:Genetic Predisposition to Disease / Q000235:genetics*; D014644:Genetic Variation / Q000235:genetics*; D006801:Humans; D000075723:Kruppel-Like Factor 6; D051741:Kruppel-Like Transcription Factors / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics*; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D011471:Prostatic Neoplasms / Q000209:etiology / Q000235:genetics* / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics*; D014407:Tumor Cells, Cultured; D023041:Xenograft Model Antitumor Assays / Q000379:methods
C105465:KLF6 protein, human; C491358:Klf6 protein, mouse; D000075723:Kruppel-Like Factor 6; D051741:Kruppel-Like Transcription Factors; D011518:Proto-Oncogene Proteins