INK4a-ARF alterations in liver cell adenoma.
BACKGROUND
The INK4a-ARF (CDKN2A) locus on chromosome 9p21 encodes two tumour suppressor proteins, p16(INK4a) and p14(ARF), whose functions are inactivated in many human cancers.


OBJECTIVE
To evaluate p14(ARF) and p16(INK4a) alterations in liver cell adenoma.


METHODS
After microdissection, DNA from 25 liver cell adenomas and corresponding normal liver tissue were analysed for INK4-ARF inactivation by DNA sequence analysis, methylation specific polymerase chain reaction, restriction enzyme related-polymerase chain reaction (RE-PCR), mRNA expression, microsatellite analysis, and immunohistochemistry. In addition, microdeletion of p14(ARF) and p16(INK4a) were assessed by differential PCR.


RESULTS
Methylation of p14(ARF) was found in 3/25 cases (12%) and alterations in p16(INK4a) occurred in 6/25 liver cell adenomas (24%) which correlated with loss of mRNA transcription. We failed to detect microdeletions or specific mutations of both exons. p16(INK4a) methylation appeared in the context of an unmethylated p14(ARF) promoter in six cases. In normal liver tissue, p14(ARF) or p16(INK4a) alterations were not observed.


CONCLUSIONS
Our data suggest that p14(ARF) methylation occurs independently of p16(INK4a) alterations in liver cell adenomas. Furthermore, methylation of p14(ARF) and p16(INK4a) may be a result of cell cycle deregulation and does not seem to be a prerequisite of malignancy.
Institute of Pathology, University of Leipzig, Liebigstr 26, 04103 Leipzig, Germany. tana@medizin.uni-leipzig.de
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Tannapfel
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Busse
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Geissler
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Witzigmann
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Hauss
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Wittekind
D018248:Adenoma, Liver Cell / Q000235:genetics*; D000483:Alleles; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000032:analysis; D019175:DNA Methylation; D005260:Female; D018628:Gene Dosage; D019942:Genes, p16; D015801:Helminth Proteins / Q000032:analysis / Q000235:genetics*; D006801:Humans; D007150:Immunohistochemistry; D008113:Liver Neoplasms / Q000235:genetics*; D008297:Male; D009124:Muscle Proteins / Q000032:analysis / Q000235:genetics*; D012189:Retrospective Studies; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D000096985:Calponins
D019941:Cyclin-Dependent Kinase Inhibitor p16; D015801:Helminth Proteins; D009124:Muscle Proteins; C118619:calponin homolog protein, Schistosoma japonicum; D000096985:Calponins