What is Cytokeratin?
Cytokeratin refers to a diverse group of intermediate filament proteins found in the intracellular cytoskeleton of epithelial tissue. They play a crucial role in providing structural support and maintaining the integrity of epithelial cells. Cytokeratins are encoded by a large multigene family and are characterized by their unique molecular weight and isoelectric point, leading to their classification into different types.
Types of Cytokeratins
Cytokeratins are broadly classified into two main types: Type I (acidic) and Type II (basic to neutral). Type I cytokeratins are encoded by genes located on chromosome 17, while Type II cytokeratins are encoded by genes on chromosome 12. These proteins form heterodimeric complexes, consisting of one Type I and one Type II cytokeratin, which then assemble into intermediate filaments.Function of Cytokeratins
Cytokeratins serve several essential functions within epithelial cells. They provide mechanical support, helping cells resist shear stress. Additionally, they are involved in cellular processes such as differentiation, polarization, and migration. Cytokeratins also play a role in signal transduction and protect cells against apoptosis.Role in Histopathology
In histopathology, cytokeratins are valuable diagnostic markers for identifying epithelial cells in tissue samples. They are commonly used in immunohistochemistry (IHC) to distinguish between different types of tumors. Cytokeratin expression patterns can help pathologists determine the origin of a carcinoma, as specific cytokeratin profiles are associated with particular types of epithelium.Commonly Used Cytokeratins in Diagnostics
Several cytokeratins are frequently used in diagnostic settings. For example, Cytokeratin 7 (CK7) and Cytokeratin 20 (CK20) are often utilized in distinguishing between different types of adenocarcinomas. CK7 is typically expressed in lung and breast carcinomas, while CK20 is commonly found in colorectal and Merkel cell carcinomas. Another example is Cytokeratin 5/6, which is usually expressed in squamous cell carcinomas.Staining Techniques
Immunohistochemistry (IHC) is the primary technique used to detect cytokeratins in tissue samples. Antibodies specific to various cytokeratins are applied to tissue sections, where they bind to their target proteins. These antibodies are then visualized using chromogenic or fluorescent detection methods, allowing pathologists to assess the presence and distribution of cytokeratins.Clinical Implications
The expression patterns of cytokeratins have significant clinical implications. For instance, the presence of specific cytokeratins can aid in the diagnosis of metastatic tumors by identifying the primary site of origin. Additionally, cytokeratin profiling can help in the classification of poorly differentiated tumors and provide prognostic information.Research Applications
Beyond diagnostic use, cytokeratins are also valuable in research. They are used to study epithelial cell biology, including cell differentiation, migration, and wound healing. Researchers also investigate the role of cytokeratins in cancer progression and metastasis, aiming to develop targeted therapies.Conclusion
Cytokeratins are indispensable tools in histology and pathology. Their unique expression patterns provide valuable information for diagnosing and understanding various epithelial tumors. As research advances, the role of cytokeratins in both clinical and experimental settings continues to expand, underscoring their importance in the field of histology.
