Basal cell carcinoma (BCC) develops predominantly in sun-exposed skin in fair-skinned individuals prone to sunburn. BCC typically occurs in adults. High exposure to ultraviolet (UV) radiation increases rate of developing BCC, a slowly growing tumor that occurs in hair-growing squamous epithelium and rarely metastasizes. In genetic studies, BCC patients have cell-cycle abnormalities of different parts of the signaling pathway. Retinoblastoma regulatory pathway is important in cell cycle arrest. In this pathway, p16INK4a, an inhibitor of Rb pathway, binds to CDK4 and CDK6 competitively with cyclin D1 to prevent phosphorylation of tumor suppressor pRB gene. Alteration of this pathway contributes to development of human cancers and also is effective in skin cancers. In this study, we analyzed mRNA expression using in situ RT-PCR and the role of immunohistochemical expression of p16INK4a in BCC.
Abnormalities of Rb-pathway components are common in the formation of cancer. The immunostaining for cyclin D1 and p16 protein was applied on 1 mm serial tissue microarray (TMA) paraffin sections. Tissue microarray (TMAs) is potentially a good method to find the molecular features of the genes and expressions of them. The aim of this study was to evaluate the protein expressions of cyclin D1 and p16 genes in squamous cell carcinomas (SCCs) of skin and compare with the normal skin tissue. Twenty-five cases of cutaneous SCCs expressed cyclin D1 and p16 proteins. All SCCs samples on the slides showed positive protein expressions of cyclin D1 and p16 genes. Our findings suggested that the increased protein expressions of cyclin D1 and p16 genes might lead to aberrant expressions of these proteins in the affected tumor cells. This study demonstrated that cell cycle controlled deregulation and uncontrolled cell cycle progression might result in the carcinogenesis.