Immunohistochemical characterization of cyclin dependent kinase-4 in different histological grades of oral leukoplakia and oral squamous cell carcinoma

BACKGROUND: Cyclin dependent kinase-4 (CDK4) encoded by CDK gene, is a heterodimer protein of cell cycle in G1-S transition. This study aimed to characterize the CDK4 immunoreactivity in different histological grades of oral leukoplakias (OLs) and oral squamous cell carcinomas (OSCCs) and also aims to discuss its probable role in the tumor biogenesis. MATERIALS AND METHODS: Expression of CDK4 was investigated in total of 52 samples including OL (15), OSCCs (30) and normal oral tissues (07). A labeled Streptavidin-Biotin immunohistochemistry assay was performed and staining intensity was evaluated. RESULTS: The staining pattern was similar in all tissues and was located in both nuclei and cytoplasm. Dysplastic epithelium displayed a progressive increase in nuclear expression of CDK4 when compared to normal tissues. Also, positive staining cytoplasm was highly evident in OSCC with loss of differentiation. CONCLUSION: Our study indicated a progressive over expression of CDK4 from normal to leukoplakias (various histological grades of dysplasias) and OSCCs.