63. Allelic Loss of Chromosome 2 in Human Oral Squamous Cell Carcinoma: Correlation with Lymph Node Metastasis

Nobuharu Yamamoto¹, Jun-etsu Mizoe, Hideyuki Numasawa², Hidetaka Yokoe³, Katsuhiro Uzawa⁴, Takahiko Shibahara², Hirohiko Tsujii, Hiroyasu Noma² and Hideki Tanzawa^{3, 4}
(¹NIRS and Tokyo Dental College; ²Tokyo Dental College; ³Chiba Univ. Hospital; ⁴Chiba Univ.)

Keywords: tumor, oral squamous cell carcinoma

To evaluate the role of chromosome 2 deletions in human oral squamous cell carcinoma (SCC) progression and to define the precise location of putative tumor suppressor genes, we examined 40 primary tumors and seven lymph node metastatic tumors from 40 patients with oral SCC by the polymerase chain reaction (PCR)-loss of heterozygosity (LOH) assay, using 10 different polymorphic loci on the long arm of chromosome 2. LOH was observed in 67.5% of the patients at one or more loci on the chromosome 2q. Two commonly deleted regions with high frequency of LOH, D2S1327 region at 2q32-35 (31.6%) and D2S206 region at 2q36 (36.7%), were identified by the deletion mapping of chromosome 2q, suggesting the presence of putative tumor suppressor genes associated with oral SCC. Examination of seven metastatic tumors also revealed four commonly deleted regions, D2S436, D2S1327, D2S155 and D2S164. Of these four regions D2S1327 region had no significant increase in the frequency of LOH between in primary tumors and in metastatic tumors. However, for the other three regions, the frequencies were much increased in metastatic tumors, compared to the results in primary tumors. In particular, very high frequencies of LOH in metastatic tumors were detected at two regions on 2q35, 100.0% at D2S155 and 57.1% at D2S164, suggesting a significant relationship between lymph node metastasis and LOH at these two regions. Our results indicate that LOH on chromosome 2q is a common event in oncogenesis and/or progression of oral SCC, and they also suggest that LOH at 2q35 plays a significant role in the lymph node metastasis.