The human organic anion transporting polypeptide 8 (SLCO1B3) gene is transcriptionally repressed by hepatocyte nuclear factor 3beta in hepatocellular carcinoma.
OBJECTIVE
The organic anion transporting polypeptides (OATPs) mediate the uptake of numerous amphipathic compounds into hepatocytes. Our aim was to study the expression and regulation of OATP8 (OATP1B3, SLC21A8/SLCO1B3) and OATP-C (OATP1B1, SLC21A6/SLCO1B1) in hepatocellular carcinomas (HCC).


METHODS
RNA and protein levels in 13 paired HCC and adjacent non-tumor liver samples were quantified by real-time polymerase chain reaction or Western blot, respectively. The OATP8 and OATP-C gene promoters were characterized by luciferase reporter assays and electrophoretic mobility shift assays (EMSA).


RESULTS
The expression of OATP8 was decreased in 60% of HCC compared to surrounding non-tumor liver tissue, on both the mRNA and protein levels. Expression of the liver-enriched transcription factor hepatocyte nuclear factor 3beta (HNF3beta) was increased in 70% of HCC and correlated inversely with OATP8 mRNA (r=-0.75, P<0.05) and protein. In contrast to OATP8, expression of OATP-C was not significantly decreased in HCC. In transfected Huh7 cells, OATP8 promoter activity was inhibited by 70% when HNF3beta was cotransfected. An HNF3beta binding site was located at nt -39/-23 by EMSA. The OATP-C promoter was not inhibited by HNF3beta.


CONCLUSIONS
HNF3beta represses transcription of the OATP8 but not the OATP-C gene, providing a mechanism for reduced expression of OATP8 in HCC.
Vavricka
Stephan R
SR
Laboratory of Molecular Gastroenterology and Hepatology, Division of Gastroenterology and Hepatology, University Hospital, CH-8091 Zurich, Switzerland.
Jung
Diana
D
Fried
Michael
M
Grützner
Uwe
U
Meier
Peter J
PJ
Kullak-Ublick
Gerd A
GA
D000368:Aged; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000503:physiopathology*; D004268:DNA-Binding Proteins / Q000235:genetics*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D051542:Hepatocyte Nuclear Factor 3-beta; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000503:physiopathology*; D027381:Liver-Specific Organic Anion Transporter 1 / Q000235:genetics; D008297:Male; D008875:Middle Aged; D009687:Nuclear Proteins / Q000235:genetics*; D029362:Organic Anion Transporters, Sodium-Independent / Q000235:genetics*; D011401:Promoter Regions, Genetic; D000074542:Solute Carrier Organic Anion Transporter Family Member 1B3; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; C496502:FOXA2 protein, human; D027381:Liver-Specific Organic Anion Transporter 1; D009687:Nuclear Proteins; D029362:Organic Anion Transporters, Sodium-Independent; C421209:SLCO1B3 protein, human; D000074542:Solute Carrier Organic Anion Transporter Family Member 1B3; D014157:Transcription Factors; D051542:Hepatocyte Nuclear Factor 3-beta