Down-regulated expression of SERPIN genes located on chromosome 18q21 in oral squamous cell carcinomas

Serpins (serine protease inhibitors) are known as a diverse family of protease inhibitors; however, various other biological activities including tumor suppression, have been recently reported for these molecules. To clarify whether members of the serpin family are involved in OSCC (oral squamous cell carcinoma), global gene screening using microarray analysis was performed with OSCC-derived cell lines. A trend toward diminished expression was shown for some SERPIN genes located on 11q12-q13.1 and 18q21. mRNA expression of SERPIN genes at these chromosome regions was therefore analyzed using real-time quantitative RT-PCR (qRT-PCR) in 55 OSCC samples and matched normal tissue. Statistically significant decreases in expression were found for SERPINB12 (P=0.001), SERPINB13 (P=0.001), SERPINB4 (P=0.042), SERPINB3 (P<0.001), SERPINB11 (P<0.001), SERPINB7 (P=0.021) and SERPINB2 (P=0.018). All of these genes are located on 18q21, the known location of the serpin gene cluster. The results strongly suggest that this chromosome region plays a crucial role in OSCC. Some serpin members in the region might be involved in tumor suppression, or there might be unidentified tumor suppressor genes within or near the chromosome region.