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Sporadic CDKN2 (MTS1/p16ink4) gene alterations in human ovarian tumours
M Schuyer1, I L van Staveren, J G Klijn
1Division of Endocrine Oncology (Department of Medical Oncology), Dr Daniel den Hoed Cancer Center, Rotterdam, The Netherlands.
Abstract:
The cell cycle regulatory proteins p16 and p21 cause cell cycle arrest at the G1 checkpoint by inhibiting activity of cyclin D-CDK4 complexes. The TP53 gene, regulating the p21 protein, is mutated at high frequency in ovarian cancer. The CDKN2 gene, encoding the p16 protein, has been mapped to chromosome 9p21 and encompasses three exons. To establish the frequency of CDKN2 gene abnormalities in ovarian tumour specimens, we have studied this gene in five ovarian cancer cell lines and in 32 primary and five metastatic ovarian adenocarcinomas. Using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and sequencing techniques both exon 1 and 2 of the CDKN2 gene, encompassing 97% of the coding sequence, were analysed. In addition, the TP53 gene was studied for the presence of mutations. The cell line HOC-7 showed a 16 bp deletion in exon 2 of the CDKN2 gene, resulting in a stop codon, whereas in cell line SK-OV-3 this gene was found to be homozygously deleted. Nine primary tumour specimens showed a migration shift on SSCP. Sequencing revealed a common polymorphism (Ala148Thr) in seven of these ovarian tumour specimens. The two other tumour samples were found to contain silent mutations, one at codon 23 (GGT-->GGA) and the other at codon 67 (GGC-->GGT). Mutations in the TP53 gene were observed in 46% of the ovarian tumour specimens. We conclude that CDKN2 gene alterations are rare events in human ovarian cancer. The low prevalence of these alterations do not allow for analysis of an association of this gene with prognosis.
Insights
Alterations in the CDKN2 gene, which regulates cell cycle protein p16, are rare in ovarian cancer. While TP53 gene mutations are common, CDKN2 gene abnormalities do not appear to be a significant factor in this disease.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Cell cycle arrest at the G1 checkpoint is regulated by p16 and p21 proteins, inhibiting cyclin D-CDK4 complexes.
- TP53 gene mutations are frequent in ovarian cancer, impacting p21 regulation.
- The CDKN2 gene encodes the p16 protein and is located on chromosome 9p21.
Purpose of the Study:
- To determine the frequency of CDKN2 gene abnormalities in ovarian tumors.
- To investigate the prevalence of TP53 gene mutations in the same specimens.
Main Methods:
- Analysis of CDKN2 gene exons 1 and 2 (97% of coding sequence) using PCR-SSCP and sequencing.
- Study of TP53 gene for mutations.
- Examination of five ovarian cancer cell lines, 32 primary, and five metastatic ovarian adenocarcinomas.
Main Results:
- One cell line (HOC-7) had a CDKN2 exon 2 deletion; another (SK-OV-3) showed homozygous deletion.
- Nine primary tumors exhibited CDKN2 migration shifts on SSCP.
- TP53 gene mutations were found in 46% of ovarian tumor specimens.
Conclusions:
- CDKN2 gene alterations are infrequent in human ovarian cancer.
- The low prevalence of CDKN2 alterations precludes prognostic association studies.
- TP53 mutations are common in ovarian cancer, unlike CDKN2 alterations.