ABSTRACT
<p><b>OBJECTIVE</b>To explore the correlation between homozygous deletions and mutation of p16 gene and the carcinogenesis and progression of squamous cell carcinoma of buccal mucosa.</p><p><b>METHODS</b>Thirty buccal cancers, 10 leukoplakias and 8 buccal mucosas were involved. DNA was extracted from the tissues. PCR was used to analyses homozygous deletion of p16 gene. PCR-SSCP-DNA sequencing was performed to detect the point mutation of p16 gene. Immunohistochemical techniques were used to detect the expression of P16 protein.</p><p><b>RESULTS</b>Gene deletions and point mutations were not found in leukoplakia and normal buccal mucosa. Gene deletions were found in 7 samples out of 30 cases of squamous cell carcinoma of buccal mucosa (23.3%), while point mutations were found in 5 samples out of 30 cases of squamous cell carcinoma of buccal mucosa (16.7%). Sequencing analysis showed that 5 cases point mutations were missense mutations, occurred on exon 2. Three cases occurred in the same point, codon 99 (GAT --> AAT). The result of immunohistochemical stains showed that 11 out of 12 cases gene inactivation did not expressed P16 protein.</p><p><b>CONCLUSION</b>Homozygous deletion and point mutation of p16 were the main pattern of gene inactivation in squamous cell carcinoma of buccal mucosa. There was a closely correlation between p16 gene inactivation and the carcinogenesis of squamous cell carcinoma of buccal mucosa.</p>