11 P - Frequent Loss of Heterozygosity at 6q in Malignant Salivary Gland Tumors

Abstract

Terminal deletions of the long arm of chromosome 6 (6q) and translocations involving the same region are the only cytogenetic event common to all histological subtypes of salivary gland carcinomas, but carcinoma ex-pleomorphic adenoma. In an attempt to characterize at the molecular level the frequency and the extension of 6q deletions in salivary gland carcinomas, we have investigated the loss of heterozygosity (LOH) at 6q in a series of 13 salivary gland carcinomas, using polymorphic DNA markers. Frozen tumor samples and the normal tissue from each patient were studied by Southern blotting and dinucleotide repeats analysis, using 13 polymorphic markers (1 at 6p, 1 centromeric, and 11 at 6q). All cases were informative for at least one <i>locus</i> at 6q. LOH was observed in 5 cases, all of them showing different histology. The highest frequency of LOH was found at <i>locus</i> D6S37 (2/6 cases) at 6q26-27. The patterns observed were compatible with terminal deletions in 3 cases and interstitial deletions in 2. Furthermore, the data suggests the existence of two distinct regions of LOH at 6q in salivary gland carcinomas. In summary, LOH al 6q was found in 38% of the cases in this series of salivary gland carcinomas. Our results support the assumption that loss of genetic material at 6q is a frequent and probably an important event in salivary gland carcinogenesis. <b>Acknowledgments</b> L.Q. was supported by the Junta Nacional de Investigação Científica c Tecnológica (JNICT). Probes p308 and phMnSOD4 were kindly provided by Prof. E. W. Jabs, and G. I. Bell, respectively.