THE RECIPROCAL TRANSLOCATION T(9-16)(Q22-P13) IS A PRIMARY CHROMOSOMEABNORMALITY IN BASAL-CELL CARCINOMAS

The reciprocal translocation t(9;16)(q22;p13) was identified in three short-term cultured basal cell carcinomas (BCCs), The t(9;16) was the sole anomaly in one clone in two tumors and was accompanied by a secon d change that also affected the long arm of chromosome 9 in the third, In addition, other cytogenetically unrelated abnormal clones were als o found in all three BCCs, The identification of t(9;16)(q22;p13) as a primary chromosomal abnormality in a subset of BCCs (we found it in 3 of 22 tumors) is especially intriguing against the background that th e PTCH gene, which when mutated in the germ line presumably gives rise to the autosomal dominant basal cell nevus or Gorlin's syndrome, maps to chromosome band 9p22. None of the genes rearranged in the BCC-spec ific t(9;16)(q22;p13) translocation have been identified, but we hypot hesize that the translocation represents the cytogenetic corollary of a tumorigenic recombination of PTCH with an as yet unknown gene in 16p 13. If so, this would be the first time that a tumor suppressor gene c ausally involved in a hereditary cancer is shown to be frequently rear ranged through a specific translocation in sporadic carcinomas of the same type.