TY - JOUR
T1 - p16INK4a promoter mutations are frequent in primary sclerosing cholangitis (PSC) and PSC-associated cholangiocarcinoma
AU - Taniai, Makiko
AU - Higuchi, Hajime
AU - Burgart, Lawrence J.
AU - Gores, Gregory J.
PY - 2002/10/1
Y1 - 2002/10/1
N2 - Background and Aims: Primary sclerosing cholangitis (PSC) predisposes individuals to cholangiocarcinoma; however, the molecular mechanisms involved in the carcinogenesis process remain unclear. Because p16INK4a inactivation has been implicated in cholangiocarcinoma, our aims were to examine PSC cholangiocytes for p16INK4a gene mutations. Methods: We studied 4 patient groups: PSC patients without cholangiocarcinoma (n = 10), patients with PSC-associated cholangiocarcinoma (n = 10), non-PSC controls (n = 10), and disease controls with primary biliary cirrhosis (n = 10). Cholangiocytes and hepatocytes were isolated from tissue sections using laser capture microdissection. Genomic DNA was extracted, and the promoter region and the 3 exons for p16INK4a were amplified by PCR and directly sequenced. Results: In the promoter region, 8-point mutations in 5 PSC cases and 14 mutations in 8 cholangiocarcinoma cases were observed. In exon 1, 1 PSC patient and 3 cholangiocarcinoma patients had point mutations. In contrast, no case had a mutation in exon 2 or 3. Mutations were not detected in cholangiocytes from control patients or primary biliary cirrhosis patients nor in hepatocytes from any of the groups; these data indicate that the observed base changes were disease specific and not genetic polymorphisms. Several of the promoter mutations (4 of 8) dramatically decreased promoter activity (<50% reduction in luciferase activity) in a reporter gene assay. Conclusions: The results show that functional point mutations in the p16INK4a promoter region likely contribute to the initiation/progression of cholangiocarcinoma in PSC. Promoter mutations in CpG islands may function as a methylation equivalent phenomenon resulting in gene inactivation.
AB - Background and Aims: Primary sclerosing cholangitis (PSC) predisposes individuals to cholangiocarcinoma; however, the molecular mechanisms involved in the carcinogenesis process remain unclear. Because p16INK4a inactivation has been implicated in cholangiocarcinoma, our aims were to examine PSC cholangiocytes for p16INK4a gene mutations. Methods: We studied 4 patient groups: PSC patients without cholangiocarcinoma (n = 10), patients with PSC-associated cholangiocarcinoma (n = 10), non-PSC controls (n = 10), and disease controls with primary biliary cirrhosis (n = 10). Cholangiocytes and hepatocytes were isolated from tissue sections using laser capture microdissection. Genomic DNA was extracted, and the promoter region and the 3 exons for p16INK4a were amplified by PCR and directly sequenced. Results: In the promoter region, 8-point mutations in 5 PSC cases and 14 mutations in 8 cholangiocarcinoma cases were observed. In exon 1, 1 PSC patient and 3 cholangiocarcinoma patients had point mutations. In contrast, no case had a mutation in exon 2 or 3. Mutations were not detected in cholangiocytes from control patients or primary biliary cirrhosis patients nor in hepatocytes from any of the groups; these data indicate that the observed base changes were disease specific and not genetic polymorphisms. Several of the promoter mutations (4 of 8) dramatically decreased promoter activity (<50% reduction in luciferase activity) in a reporter gene assay. Conclusions: The results show that functional point mutations in the p16INK4a promoter region likely contribute to the initiation/progression of cholangiocarcinoma in PSC. Promoter mutations in CpG islands may function as a methylation equivalent phenomenon resulting in gene inactivation.
UR - http://www.scopus.com/inward/record.url?scp=0036771842&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0036771842&partnerID=8YFLogxK
U2 - 10.1053/gast.2002.36021
DO - 10.1053/gast.2002.36021
M3 - Article
C2 - 12360471
AN - SCOPUS:0036771842
SN - 0016-5085
VL - 123
SP - 1090
EP - 1098
JO - Gastroenterology
JF - Gastroenterology
IS - 4
ER -