Localization of a novel tumor suppressor gene loci on chromosome 9p21-22 in oral cancer.

Allelic imbalance or loss of heterozygosity (LOH) studies have been used to identify regions on chromosomes that may contain putative tumor suppressor genes. Deletions of chromosome 9 regions have been observed at high frequency in many other types of sporadic tumor, whereas in oral cancer no decisive information about the allelic loss on chromosome 9 has been reported. To provide detailed understanding of the genetic alterations in oral cancer, 24 highly polymorphic markers mapped on chromosome 9 were used to examine 34 cases of oral squamous cell carcinoma (SCC). LOH was detected in 18 (53%) of 34 informative samples at one or more loci examined. On the basis of our results, three commonly deleted regions were identified and a detailed deletion map was constructed. One of the novel regions was on 9p22, where a tumor suppressor gene, interferon a cluster (IFNA) gene, was identified before. Another region was D9S157 locus at 9p22, telomeric to IFNA locus and p15/16 genes, and the third was located on 9p21 of the D9S104 locus, centromelic to methylthioadenosine phosphorylase (MTAP) gene and p15/16 genes. Thus, our data suggest that, except for p15/16 and MTAP gene, there were at least two candidate tumor suppressor genes located at chromosome 9p, and that the alteration of these genes is associated with the tumorigenesis of oral SCC.