Related Experiment Videos
Alterations of the p16(INK4) locus in human malignant mesothelial tumors
Tomoko Hirao1, Raphael Bueno, Chang-Jie Chen
1Department of Cancer Cell Biology, Harvard School of Public Health, Boston, MA 02115, USA.
Abstract:
The INK4 locus has two promoters and encodes two unique proteins that share exons in different reading frames, p16(INK4a) and p14(ARF). The p16(INK4a) protein, by inhibiting cyclin-dependent kinase, down regulates Rb-E2F and leads to cell cycle arrest in the G1 phase. The p14(ARF) protein interacts with the MDM2 protein, neutralizing MDM2-mediated degradation of p53. Since p53/Rb genes are not altered in malignant mesothelioma, additional components of these pathways, such as p16(INK4a) and p14(ARF), are candidates for inactivation. In this study, we have examined p16(INK4a) and p14(ARF) alterations (gene deletion, mutation and promoter methylation) in 45 primary malignant mesothelioma specimens. Fourteen patients (31%) had altered p16; four tumors had a methylated promoter region (8.8%), 10 tumors showed p16 to be deleted (22.2%), and one tumor had a point mutation (2%). We did not find any instances of methylation in the p14(ARF) 5'-CpG island. Patients whose tumors had p16 deletion were significantly younger than those with methylation, and, in the patients whose lungs were studied for the prevalence of asbestos fibers, those with any p16 alteration had lower fiber counts than those with no p16 alteration. Hence, p16 gene alteration is relatively common in malignant mesothelioma, while p14(ARF) is rarely, if ever, methylated. Our data suggest that deletion of p16 occurs in a relatively susceptible subset of the population.
Insights
Alterations in the p16 gene are common in malignant mesothelioma, affecting 31% of patients. The p14ARF gene shows rare methylation, suggesting p16 gene deletion impacts a susceptible population.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- The INK4 locus encodes p16INK4a and p14ARF proteins, critical regulators of cell cycle control.
- p16INK4a inhibits cyclin-dependent kinases, arresting the cell cycle at G1 phase.
- p14ARF stabilizes p53 by inhibiting MDM2-mediated degradation.
- Malignant mesothelioma often involves alterations in cell cycle regulatory pathways.
Purpose of the Study:
- To investigate alterations in p16INK4a and p14ARF genes in malignant mesothelioma.
- To determine the frequency of gene deletion, mutation, and promoter methylation for these genes.
Main Methods:
- Analysis of 45 primary malignant mesothelioma specimens.
- Examination of p16INK4a and p14ARF gene alterations, including deletion, mutation, and promoter methylation.
- Correlation of genetic alterations with patient age and asbestos fiber burden.
Main Results:
- p16INK4a alterations were found in 31% of tumors: 8.8% promoter methylation, 22.2% deletion, and 2% point mutation.
- No instances of p14ARF promoter methylation were detected.
- Patients with p16 deletion were younger than those with methylation.
- Tumors with any p16 alteration showed lower asbestos fiber counts.
Conclusions:
- p16 gene alteration is relatively common in malignant mesothelioma.
- p14ARF promoter methylation is rare in this cancer.
- p16 gene deletion may occur in a susceptible population subset, potentially linked to environmental factors.