FREQUENT LOSS OF CHROMOSOME 9P21-22 EARLY IN HEAD AND NECK-CANCER PROGRESSION

In order to define more clearly the role of chromosome 9 loss in head and neck squamous cell carcinoma (HNSCC), 29 invasive carcinomas and 1 7 preinvasive lesions were analyzed for loss of heterozygosity (LOH) o n chromosome 9. We found LOH in 21 of 29 (72%) HNSCC tumors using high ly polymorphic microsatellite markers. In 17 of 21, LOH was found at a ll informative sites on the p arm with no LOH of the q arm. Further ma pping in tumors, with partial LOH of the 9p arm, localized a common re gion of loss between markers D9S165 and D9S156. Deletion of this regio n on chromosome 9 has been found in several other tumor types implying the presence of a tumor suppressor gene at this locus. The inactivati on of a tumor suppressor gene an chromosome 9p may represent the most commonly described genetic alteration in HNSCC. A similar incidence of allelic loss on chromosome 9p was identified in 12 of 17 (71%) preinv asive lesions. The identical frequency of loss in preinvasive and inva sive lesions suggests that loss of 9p is an early event in HNSCC progr ession.