Basic and clinical research for prevention of carcinogenesis aiming at extinction of head and neck squamous cell carcinoma.

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Head and neck squamous cell carcinomas (HNSCC) manifest various clinical behaviors according to their origin, i.e., each part of the head and neck mucosa. However, differences of genetic factors involved in the carcinogenesis of head and neck squamous cell carcinoma (HNSCC) in each part of the head and neck have not yet been sufficient for study and evaluation. Three hundred and two samples of HNSCC were used to determine the allelic loss of certain areas of the genome, i.e., 3p21, 9p21 and 17p13, and to examine whether genetic factors are correlated with the tissue specificity of HNSCC and influence the clinical features of the patients. When loss of heterozygosity (LOH) at 3p21, 9p21 and 17p13 were examined, LOH was detected in 54.5%, 57.4% and 57.1% of the informative cases, respectively. The frequencies of LOH in hypopharyngeal and in laryngeal cancer were significantly higher than that in oral cancer. There were significant correlations between 3p21 LOH and lymph node involvement and 17p13 LOH and tumor size, resulting in the positive implication of clinical stage of the patients. These results indicate that not only the function of the tumor suppressor genes were different among these HNSCC in different regions but also that allelic loss plays a key role in the acquisition of malignant phenotype of the tumor.On the other hand, patients who had LOH positive cancer significantly had the poorer prognosis than those who had LOH negative tumor, indicating that allelic loss has a key role in acquisition of the malignant phenotype of the tumor to show the poorer prognosis of the patients who have the LOH positive tumor.