Aberrant expression of cyclin A and cyclin B1 proteins in oral carcinoma

Cyclins play an important role in regulating the passage of dividing cells through critical checkpoints in the cell cycle. Aberrant expression of cycl in proteins has been found in a number of human cancers, including carcinom as of the head and neck, where amplification of the cyclin D1 gene is a com mon finding. The objective of this study was to examine cell cycle kinetics in oral carcinomas by determining the expression of the S phase protein cy clin A and the M phase protein cyclin BI. Routinely processed tissue sectio ns of 50 oral squamous cell carcinomas from the floor of the mouth were sta ined by immunohistochemistry for cyclin A, cyclin B1 and Ki-67 proteins. Te n specimens of normal epithelium from the floor of the mouth were used as c ontrols. The number of cells showing nuclear staining for cyclin A, cyclin B1 and Ki-67 proteins was determined by computer image analysis. There were 17 well-differentiated, 25 moderately differentiated and 8 poorly differen tiated tumours. Mean counts for cyclin A (29.50+/-4.10, mean+/-95% CI), cyc lin B1 (2.05+/-0.30) and Ki-67 (49.46+/-5.91) proteins in the carcinomas we re significantly higher than counts for the normal epithelial controls (cyc lin A: 9.30+/-1.72; cyclin BI: 1.01+/-0.36; Ki-67: 17.40+/-4.17). For cycli n A, cyclin B1 and Ki-67, mean staining scores for all tumour grades were s ignificantly higher than controls. There was a strong correlation between K i-67 and cyclin A scores in all tumour groups (r(2) = 0.68); however, the c orrelations between cyclin 1 and cyclin A scores (r(2) = 0.35) and between cyclin B1 and Ki-67 scores (r(2) = 0.39) were weak. We conclude that there is overexpression of cyclin A and cyclin B1 proteins in oral carcinoma. Fur thermore, the poor correlations for cyclin B1 scores with other cell cycle indices suggest that there may be aberrant cell cycle progression at the G2 /M checkpoint in oral carcinomas.