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Genetic and epigenetic alterations of the INK4a–ARF pathway in cholangiocarcinoma
Author(s) -
Tannapfel Andrea,
Sommerer Florian,
Benicke Markus,
Weinans Lars,
Katalinic Alexander,
Geißler Felix,
Uhlmann Dirk,
Hauss Johann,
Wittekind Christian
Publication year - 2002
Publication title -
the journal of pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.964
H-Index - 184
eISSN - 1096-9896
pISSN - 0022-3417
DOI - 10.1002/path.1139
Subject(s) - biology , locus (genetics) , microdissection , cancer research , methylation , gene , microbiology and biotechnology , exon , dna methylation , epigenetics , promoter , loss of heterozygosity , retinoblastoma protein , tumor suppressor gene , carcinogenesis , cell cycle , genetics , allele , gene expression
The INK4a–ARF locus, located on chromosome 9p21, encodes two cell‐cycle regulatory proteins, p16 INK4a and p14 ARF , acting through the Rb–CDK4 and p53 pathways. To study the contribution of each pathway in the tumourigenesis of cholangiocarcinoma, the alterations of p14 ARF , p16 INK4a , p53, and pRb were analysed. After microdissection, DNAs from 51 cholangiocarcinomas were analysed by methylation‐specific PCR (MSP), restriction‐enzyme related polymerase chain reaction (RE‐PCR), microsatellite analysis, mRNA expression, and DNA sequencing. Immunohistochemistry of p14 ARF , p16 INK4a , p53, and pRb was also performed. Promoter methylation of p14 ARF was found in 13/51 cases (25%) and p16 INK4a showed aberrant promoter methylation in 39/51 cases (76%) which correlated with loss of mRNA transcription. Two tumours (4%) had homozygous deletion of the INK4a–ARF locus. Specific mutations of both exons were not detected. p14 ARF inactivation appeared in the context of an unmethylated p16 INK4a promoter in eight of 13 cases (61%) of the carcinomas methylated at p14 ARF . Mutations of p53 were found in 19 of 51 tumours (37%), and four of them (21%) harboured p14 ARF inactivation. The pRb protein was detected in 30/51 (59%) tumours examined. The absence of pRB protein did not correlate with any of the examined parameters. Alterations of the INK4a–ARF locus, pRB or p53 status could not be established as independent prognostic factors in these tumours. These findings indicate that the INK4a–ARF locus is frequently inactivated in cholangiocarcinoma of the liver and occurs independently of the status of p53 or pRb. Copyright © 2002 John Wiley & Sons, Ltd.