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Published on: January 3, 2013
Immunohistochemical and Molecular Study of p16INK4A Expression in Pituitary Adenoma
Hanan M Abd El-Moneim1, Dalia Abd El-Rehim
1The Department of Pathology, Faculty of Medicine, El-Minia University, Egypt.
Background And Objectives:
Pituitary adenomas comprise 10-25% of primary intracranial tumours. The molecular mechanisms underlying their development and progression have not yet been clearly defined. P16INK4A is frequently disrupted in human tumors including pituitary adenomas. Our aim was to evaluate the expression of P16 protein expression and its relation with gene methylation in pituitary adenoma development and progression.
Material And Methods:
Immunohistochemistry was performed on 34 formalin fixed paraffin embedded specimens of pituitary adenoma. The p16INK4A gene methylation status was screened using an enzyme restricted polymerase chain reaction.
Results:
Loss of p16 protein expression occurred in 19/34 (55.9%) and P16INK4A methylation was detected in 14/34 (41.2%) of tumor samples. Both p16INK4A methylation and lack of p16 immunoreactivity were significantly related to larger tumor size and increased grade. Patients with either p16-negative or methylated tumors were significantly older than patients with p16-positive or unmethylated tumors. A significant positive correlation between loss of p16 protein expression and p16INK4A gene methylation was found.
Conclusion:
These data suggest that p16 downregulation is a common event in pituitary adenoma and that its alteration might play an important role in genesis, growth progression, and biological behavior of pituitary adenomas. Our findings could imply that hypermethylation of the p16INK4A gene; represents the major target and perhaps a required epigenetic event in human pituitary tumorigenesis.
Key Words:
Immunohistochemistry - Methylation - P16INK4A - Pituitary adenoma.
Insights
Loss of p16 protein expression and P16INK4A gene methylation are common in pituitary adenomas, correlating with tumor size and grade. These alterations may drive pituitary tumor development and progression.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Pituitary adenomas are common intracranial tumors with unclear molecular pathogenesis.
- The P16INK4A gene is frequently altered in human cancers, including pituitary adenomas.
- Understanding P16INK4A alterations is crucial for elucidating pituitary adenoma development.
Purpose of the Study:
- To investigate P16 protein expression in pituitary adenomas.
- To assess the methylation status of the P16INK4A gene in pituitary adenomas.
- To correlate P16INK4A alterations with pituitary adenoma characteristics.
Main Methods:
- Immunohistochemistry was used to evaluate p16 protein expression in 34 pituitary adenoma specimens.
- Enzyme-restricted polymerase chain reaction screened the P16INK4A gene methylation status.
- Tumor size, grade, and patient age were analyzed in relation to p16 status.
Main Results:
- Loss of p16 protein expression was observed in 55.9% of samples.
- P16INK4A methylation was detected in 41.2% of tumor samples.
- Both P16INK4A methylation and lack of p16 expression correlated with larger tumor size, increased grade, and older patient age.
Conclusions:
- P16 downregulation is a frequent event in pituitary adenomas, potentially impacting tumor behavior.
- P16INK4A gene hypermethylation may be a key epigenetic event in pituitary tumorigenesis.
- These findings highlight the role of p16 alterations in pituitary adenoma development and progression.
