LOSS OF HETEROZYGOSITY STUDIES IN SQUAMOUS-CELL CARCINOMAS OF THE HEAD AND NECK

Background. Loss of heterozygosity (LOH) studies have been pivotal in identifying tumor suppressor genes involved in the pathogenesis of a n umber of cancers. In squamous cell carcinomas of the head and neck reg ion (SCCHN), LOH studies using the Southern blot technique are scarce. Methods. SCCHNs were obtained immediately after surgical resection fr om 78 patients. Histologic confirmation was made by frozen section and tumors with less than 50% malignant cells were excluded. DNA was dige sted with restriction enzymes, and after Southern blotting the membran es were hybridized with radiolabeled probes. Chromosome arms analyzed included 1p, 3p, 4p, 5q, 8p, 10p, 11p, 11q, 13q, 17p, 17q, 18q, 21q, a nd 22q. Results. The average rate of LOH was 25% per chromosome arm. S ignificantly higher rates of LOH were observed for chromosome arms 5q (56%) and 17p (45%), Other investigators have reported high rates of L OH for the H- ras-l locus, and chromosome arms 11p, 11q, and 13q. Howe ver, these results were not confirmed in this study. For patients with stage 1 or 2 tumors, the overall LOH rate was 13%, and for patients w ith stage 3 or 4 disease the rate was 23%. This difference was statist ically significant (p < 0.025). Conclusions. As tumors progress to hig her stages, they appear to accumulate an increasing number of genetic abnormalities. Chromosome arms 5q and 17p contain tumor suppressor gen es which are likely to be involved in the pathogenesis of SCCHN.