Applications of Cytokeratin Expression in the Diagnosis of Oral Diseases

All mammalian cells have a complex intracytoplasmic cytoskeleton made up of three main structural units and related proteins, tubulin containing microtubules, actin containing microfilaments, and Intermediate Filaments (IF). There are six types of IFs; cytokeratin fibres consisting of type I and type II IFs. Cytokeratins (CK), comprising of collections of IFs that are explicitly communicated by epithelial tissues^. There are 20 unique polypeptides of CK expressed by epithelium that have been indexed based on their molecular weight (range 40-70 kDa).

CK and associated filaments give a framework to epithelial cells and tissues to maintain their structural integrity. Thus, ensure mechanical resilience, sustain stress, establish cell polarity, and to protect against variations in hydrostatic pressure.

Genetic encoding of cytokeratins shows homogeneous nucleotide sequence. 54 genes are responsible for encoding of cytokeratin in humans which are congregated on chromosome no. 2. Genetic mutation of cytokeratins is important for pathophysiology of various mucocutaneous disorders, which is mostly autosomal dominant. Patterns and types of cytokeratin expression are very specific and important in tumour typing. Thus, cytokeratin expression is considered as one of the most potent tumour markers of epithelial differentiation in the field of cell biology and surgical pathology.

Oral squamous cell carcinoma is histopathologically graded as well, moderate, poorly differentiated squamous cell carcinoma on the basis of differentiation of neoplastic cells. In case of poorly differentiated oral squamous cell carcinoma, it is critical to identify the phenotype of cell. Thus, differentiation of carcinoma from sarcomas is challenging. As the management protocol and prognosis of carcinoma and sarcoma is varied so diagnosis is mandatory at initial stage. Thus, CK plays an important role in oral squamous cell carcinoma. Apart from this, it has a role in odontogenic pathology and salivary gland pathology.

Expression of these cytokeratins in odontogenesis indicates that they have significant role in embryonic development. Different patterns of expression of keratin help in identification of cells as epithelial cells and also identifies different phases during epithelial differentiation. Antibodies against these cytokeratins can be used to explain the histogenesis and to distinguish the tumours.

Thus, the field of cytokeratins is dynamic and fascinating. Cytokeratins and corresponding genes, function as etiological components, analytic markers and prognosticators.