Loss of heterozygosity at chromosome 1q22 in basal cell carcinomas and exclusion of the basal cell nevus syndrome gene from this site.

Basal cell carcinomas, the most common human tumors, generally appear sporadically and in small numbers. Rarely, they may appear in great numbers and at an earlier age as a manifestation of the basal cell nevus syndrome, an autosomal dominant inherited disorder. Drawing on the retinoblastoma paradigm, we have begun a search for tumor suppressor genes important in the development of basal cell carcinomas by comparing DNA of tumors and normal cells. Loss of heterozygosity, a frequent marker of the site of tumor suppressor genes, was found at chromosome 1q in one-third of the tumors studied. However, comparison of the inheritance of DNA markers versus the inheritance of the basal cell nevus syndrome is one large kindred excluded this area of chromosome 1q as the site of the gene whose abnormality causes this hereditary disease. These data suggest that large deletions may accompany the development of cutaneous, low grade tumors just as they accompany the development of visceral, high grade cancers.