Related Experiment Videos
CDKN2A/p16 inactivation in the prognosis of oligodendrogliomas
S Bortolotto1, L Chiadò-Piat, P Cavalla
1Division of Neurology, Department of Neuroscience, University of Turin, Turin, Italy.
Abstract:
The cell-cycle regulator p16 inhibits the complex cdk4-cyclin D1 and controls G1-S transition. In human tumors, p16 inactivation is often accomplished by homozygous deletion (HD) of its encoding gene, CDKN2A. Methylation of the 5' CpG island promoter has been proposed as an alternative mechanism of inactivation. Expression of p16, CDKN2A HD and 5' CDKN2A CpG island methylation was studied in 25 oligodendrogliomas by immunohistochemistry and PCR amplification. Ten oligodendrogliomas were p16-immunonegative, and CDKN2A HD was determined in 8 of these cases. In the 2 immunonegative cases without HD, no CpG island methylation was found. The absence of CpG island methylation in the p16-immunonegative cases without HD suggests either non-genetic regulation of p16 or different genetic changes. CDKN2A HD did not correlate with histological grading (p = n.s.); however, it showed a correlation with survival (p = 0.03), supporting an important role of CDKN2A in the prognosis of oligodendrogliomas.
Insights
The cell cycle regulator p16 gene deletion (CDKN2A HD) is linked to poorer survival in oligodendrogliomas. Methylation of the 5'CpG island promoter was not found to be an alternative inactivation mechanism in these tumors.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- The cell-cycle regulator p16 (encoded by CDKN2A) is crucial for controlling the G1-S transition.
- In human tumors, p16 inactivation frequently occurs via homozygous deletion (HD) of the CDKN2A gene.
- promoter methylation has been suggested as an alternative inactivation pathway.
Purpose of the Study:
- To investigate the mechanisms of p16 inactivation in oligodendrogliomas.
- To determine the correlation between CDKN2A alterations, p16 expression, and clinicopathological features, including survival.
Main Methods:
- Immunohistochemistry was used to assess p16 expression.
- Polymerase chain reaction (PCR) amplification was employed to detect CDKN2A homozygous deletion (HD) and 5'CpG island methylation.
- The study analyzed 25 oligodendroglioma samples.
Main Results:
- Ten out of 25 oligodendrogliomas were p16-immunonegative.
- CDKN2A HD was identified in 8 of the p16-immunonegative cases.
- No 5'CpG island methylation was detected in the p16-immunonegative cases lacking HD, suggesting alternative inactivation mechanisms or regulation.
- CDKN2A HD showed a significant correlation with poorer patient survival (p = 0.03) but not with histological grading.
Conclusions:
- CDKN2A homozygous deletion is a significant prognostic factor in oligodendrogliomas.
- The absence of promoter methylation in p16-immunonegative cases without HD points to other potential genetic or regulatory mechanisms of p16 inactivation.
- Further research is needed to elucidate these alternative pathways.