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Alterations of CDKN2 (p16) in non-small cell lung cancer
S de Vos1, C W Miller, S Takeuchi
1Department of Hematology/Oncology, Cedars-Sinai Medical Center, UCLA School of Medicine 90048, USA.
Abstract:
The cyclin-dependent kinase inhibitor known as p16 (CDK41, CDKN2, INK4A, MTS1) has been proposed as a tumor suppressor gene on chromosome segment 9p21. We have evaluated CDKN2 alterations in 34 non-small cell lung cancers (NSCLCs) with matched normal tissue controls and in 9 NSCLC cell lines by Southern blotting, single-strand conformation polymorphism (SSCP) with the polymerase chain reaction, and direct sequencing. In addition, loss of heterozygosity at chromosome segment 9p21, with the use of the microsatellite marker D9S171, was studied in these samples. Whereas CDKN2 was either deleted or mutated in NSCLC cell lines at a high frequency (6/9, 67%), alterations were much less frequent (7/34, 21%) in primary tumor samples. Only one sample contained a point mutation in exon 1 of CDKN2. In addition, two samples had homozygous deletions of CDKN2 in exon 1; one had a homozygous and three a hemizygous deletion of exon 2. Possibly normal tissue contaminating our tumor samples may have masked homozygous deletions in these cases. Four patient samples had LOH in the region of CDKN2 on chromosome segment 9p21; two of these samples had potentially inactivating alterations of CDKN2; one sample had a mutation of CDKN2, and the other had a homozygous deletion of exon 1. In summary, inactivation of CDKN2 is implicated in the development of about 20% of NSCLC, but the possibility of another tumor suppressor gene on chromosome segment 9p21 important in lung cancer cannot be eliminated.
Insights
The cyclin-dependent kinase inhibitor p16 (CDKN2) shows alterations in 21% of non-small cell lung cancers (NSCLCs). CDKN2 inactivation is implicated in NSCLC development, though other tumor suppressor genes on chromosome 9p21 may also be involved.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- The p16 gene (CDKN2A), a cyclin-dependent kinase inhibitor, is a suspected tumor suppressor located on chromosome 9p21.
- Alterations in tumor suppressor genes are critical in the development of various cancers, including non-small cell lung cancer (NSCLC).
Purpose of the Study:
- To investigate the frequency and nature of alterations in the CDKN2 gene in non-small cell lung cancer (NSCLC).
- To assess the role of CDKN2 inactivation in the pathogenesis of NSCLC.
Main Methods:
- Analysis of CDKN2 alterations in 34 primary NSCLC tumors and 9 NSCLC cell lines using Southern blotting, PCR-SSCP, and direct sequencing.
- Evaluation of loss of heterozygosity (LOH) at chromosome 9p21 using the microsatellite marker D9S171.
Main Results:
- CDKN2 alterations (deletions or mutations) were found in 67% of NSCLC cell lines but only in 21% of primary tumor samples.
- Loss of heterozygosity (LOH) at 9p21 was observed in four patient samples, with two showing potentially inactivating CDKN2 alterations.
- A single point mutation and various homozygous/hemizygous deletions of CDKN2 were identified in primary tumors.
Conclusions:
- CDKN2 inactivation is implicated in the development of approximately 20% of NSCLC cases.
- The study suggests that other tumor suppressor genes on chromosome 9p21 may also play a significant role in lung cancer development.