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Immunohistochemical survey of p16INK4A expression in normal human adult and infant tissues
G P Nielsen1, A O Stemmer-Rachamimov, J Shaw
1Department of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston, USA.
Abstract:
p16INK4A is a cell cycle inhibitor that is commonly inactivated in human tumors and tumor cell lines. Despite its importance in human neoplasia, the normal pattern of p16 expression remains largely unknown. Therefore, we analyzed the immunohistochemical localization of p16 in all human organs and demonstrated that cellular p16 expression is highly selective. In adults, proliferative endometrium, breast ductal epithelium, squamous and tubal metaplastic epithelium of the uterine cervix, esophageal squamous epithelium, salivary glands, and antral gastric glands all strongly express the protein. p16 is also widely expressed in endocrine glands, including Langerhans cells in the pancreas and anterior pituicytes and Leydig and Sertoli cells in testis. Within each tissue, however, p16 expression does not correlate with cellular proliferation or maturation. In infants, p16 staining was limited to thymic Hassall's corpuscles, occasional thymic lymphocytes, and only rare pancreatic epithelial cells. Therefore, increased expression of p16 in adult tissues, as in mouse tissues, may reflect a role of p16 in cellular senescence. Restriction of p16 expression in infants to the thymus, the only organ committed to early senescence, is also consistent with such a role. Documentation of the pattern of p16 expression in normal tissues will contribute to our understanding of the normal function of this protein and to interpretation of potentially altered p16 expression in human tumors.
Insights
The cell cycle inhibitor p16INK4A shows selective expression in adult human organs, not correlating with proliferation. Its restricted infant expression suggests a role in cellular senescence.
Area of Science:
- Oncology
- Cell Biology
- Immunohistochemistry
Background:
- p16INK4A is a crucial cell cycle inhibitor frequently inactivated in human tumors.
- The normal expression pattern of p16INK4A across human tissues is largely uncharacterized.
- Understanding normal p16INK4A expression is vital for interpreting its alterations in neoplasia.
Purpose of the Study:
- To map the immunohistochemical localization of p16INK4A in all human organs.
- To determine the normal pattern of p16INK4A protein expression in adult and infant tissues.
- To investigate the potential role of p16INK4A in cellular senescence.
Main Methods:
- Immunohistochemical analysis of p16INK4A expression.
- Examination of tissue samples from adult and infant human organs.
- Correlation analysis between p16INK4A expression, cellular proliferation, and maturation.
Main Results:
- p16INK4A exhibits highly selective expression in specific adult tissues, including endometrium, breast, cervix, esophagus, salivary glands, and gastric glands.
- Widespread p16INK4A expression is observed in adult endocrine glands and reproductive organs.
- Infant p16INK4A expression is notably restricted to the thymus and pancreas, differing significantly from adult patterns.
- p16INK4A expression levels did not correlate with cellular proliferation or maturation within tissues.
Conclusions:
- The distinct expression pattern of p16INK4A in adult tissues, particularly its restricted expression in infants, supports a role in cellular senescence.
- Documenting normal p16INK4A expression aids in understanding its physiological functions and aberrant expression in tumors.
- This study provides a foundational reference for p16INK4A expression in normal human tissues.
