Journal Article

Genetic status of cell cycle regulators in squamous cell carcinoma of the oesophagus: the <i>CDKN2A</i> (<i>p16</i><sup><i>INK4a</i></sup> and <i>p14</i><sup><i>ARF</i></sup> ) and <i>p53</i> genes are major targets for inactivation

Johanna Smeds, Petra Berggren, Xin Ma, Zhijian Xu, Kari Hemminki and Rajiv Kumar

in Carcinogenesis

Volume 23, issue 4, pages 645-655
Published in print April 2002 | ISSN: 0143-3334
Published online April 2002 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/23.4.645
Genetic status of cell cycle regulators in squamous cell carcinoma of the oesophagus: the CDKN2A (p16INK4a and p14ARF ) and p53 genes are major targets for inactivation

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We determined inactivation of the CDKN2A (p16INK4a and p14ARF) gene in 21 cases of oesophageal squamous cell carcinoma (OSCC). The tumours were also analysed for mutations in exons 5–8 and allelic losses in the p53 gene. In addition, we screened the CDKN2B (p15 INK4b), CDKN2C (p18 INK4c), CDK4 and p53R2 genes for mutations in the tumour tissues. Besides concomitant alterations in the CDKN2A and p53 loci in more than half of the cases, our results showed that in 18 OSCC (86%) the CDKN2A (p16INK4a and p14ARF ) gene was affected through mutations, homozygous/hemizygous deletions and promoter hypermethylation. Eight out of 10 tumours with mutations or promoter hypermethylation specific to the CDKN2A/p16 INK4a gene showed loss of the wild-type allele. One tumour with a single base deletion in the N-terminus (codon 8) of the CDKN2A/p16INK4a gene carried a novel germ-line mutation or a rare polymorphism (Ile51Met) in exon 2 of the CDK4 gene. Promoter hypermethylation in the CDKN2A/p14 ARF gene was detected in 11 tumours. In the p53 gene 15 mutations were detected in 14 tumours. We detected an inverse relationship between CDKN2A/p16 INK4a inactivation and frequency of loss of heterozygosity at the p53 locus (OR 0.09, 95% CI 0.01–0.98; Fisher exact test, P-value ~0.03). Screening of nine exons of the p53R2 [Human Genome Organisation (HUGO) official name RRM2B] gene resulted in identification of a novel polymorphism in the 5′ untranslated region, which was detected in four cases. Our results suggest that the CDKN2A (p16INK4a and p14ARF ) and p53 genes involved in the two cell cycle pathways are major and independent targets of inactivation in OSCC.

Keywords: ARF, p14ARF; LOH, loss of heterozygosity; OSCC, oesophageal squamous cell carcinoma; p16, p16INK4a.

Journal Article.  8875 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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