The relationship between overexpression of cyclin D1 and prognostic factors on pharyngeal cancer. (molecular biological approach)

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Cyclin D1 is a cell cycle regulator essential for G1-S phase progression. The gene is located on chromosome llq13, which the abnormal amplification has been observed in many tumor cells. It also complexes with many other cell cycle related proteins such as cdk4, PCNA, and makes a cyclin box, which regulates the cell cycle. In this study, we have analyzed cyclin D1 mRNA amplification and protein overexpression in a series of human pharyngeal carcinomas using immunohistochemical and molecular biological methods. The results were analyzed against the clinical and pathological characteristics of the patients.A strong correlation was observed between the cyclin D1 and cdk4 mRNA amplification, suggesting that these genes would be amplified in the same phase in the tumor cell cycles. Also, we found that strong overexpressions of the cyclin D1 protein were seen not only in the poorly differentiated carcinomas, but also in the well-differentiated carcinomas. It suggests that the other genes in this amplicon may also be involved in the progression and differentiation of carcinogenesis. Additionally, we analyzed that the expression of cyclin D1 and cdk4 mRNA amplification had a correlation with the overexpression of PCNA protein. This data are consistent with the notion that the expression of cyclin D1 and cdk4 represents an important role of the cell regulation in pharyngeal carcinomas.