ALLELIC IMBALANCE ON CHROMOSOME 3P IN ORAL DYSPLASTIC LESIONS - AN EARLY EVENT IN ORAL CARCINOGENESIS

We have demonstrated previously a loss of constitutional heterozygosit y on the short arm of chromosome 3 in similar to 50% of oral squamous cell carcinomas. In the present study, we have investigated 30 oral dy splastic lesions (DLs), presenting clinically as either erythroplakias or leukoplakias with histopathological features of either severe epit helial dysplasia or carcinoma in situ, for LOH on chromosome 3p using 15 microsatellite markers. Thirteen of the 30 DLs (similar to 43%) sho wed allelic imbalance at one or more loci. The pattern of loss in thes e lesions defined three noncontiguous regions of interstitial deletion s that overlap with those defined for oral squamous cell carcinomas. T hese data indicate that the alteration of tumor suppressor genes on ch romosome 3p is probably an early event in oral carcinogenesis. Additio nally, 7 of the 30 DLs showed microsatellite instability. However, the frequency of loci showing microsatellite instability per lesion was l ow.