Frequent cyclin D1 gene amplification and protein overexpression in oral epithelial dysplasias

Amplification of the cyclin D1 gene has been identified in 17-55% of head a nd neck squamous cell carcinoma. In some tumors, this alteration has been a ssociated with decreased survival and increased recurrence rates. In precan cerous lesions of the mouth, the frequency of cyclin D1 gene amplification is not known. In addition, it is unknown whether amplification of the gene translates to overexpressed cyclin D1 protein in these lesions. We examined 59 formalin-fixed, paraffin embedded tissue biopsies of oral epithelial dy splasias (OED) and 25 oral squamous cell carcinoma (SCC) from the floor of the mouth for cyclin D1 gene and protein levels. Genomic DNA was extracted from laser microdissected lesional tissue and a duplex, quantitative PCR as say was used to determine the amplification of the cyclin D1 gene relative to interferon-gamma. Cyclin D1 protein expression was determined using immu nohistochemistry and counting positive nuclei by computer image analysis. W e found cl;clin D1 gene amplification in 41% of mild, 45% of moderate and 2 4% of severe OEDs. Cyclin D1 was amplified in 36% of SCC. Overexpression of cyclin D1 protein was identified in 29% of mild, 47% of moderate, 29% of s evere OED's, and in 32% of SCC. Overexpression of cyclin D1 protein was ide ntified in similar proportions of all grades of dysplasia and SCC. There we re statistically significant correlations identified between gene and prote in levels in all categories of disease. We concluded that amplification of the cyclin D1 gene is frequent in OED and that duplex, quantitative polymer ase chain reaction is a reliable method to detect this change in routinely processed biopsies. The strong correlation between cyclin D1 gene amplifica tion and protein levels suggests that this method may be suitable to assess cyclin D1 gene status in tissues not suitable for protein analysis. (C) 20 01 Elsevier Science Ltd. All rights reserved.