Identification of Caspase-6 as a Candidate Tumor Suppressor Gene at 4q25 in Oral Cancer

We recently reported the frequent deletion of chromosome 4q25 region in oral squamous cell carcinoma and discussed the Caspase-6 as a possible tumor suppressor gene in this region due to its near location to this hot spot. We this time examined the role of Caspase-6 in oral cancers. mRNA expression level, protein localization and gene mutation of Caspase-6 were analyzed. Reverse-transcription-PCR analysis demonstrated decreased expression in 40% and equal expression in 30% of Caspase-6 mRNA of primary tumors as compared with that matched normal samples. cDNA sequencing analysis of Caspase-6 did not reveal any somatic mutation. Caspase-6 protein localization was in similar proportion with its mRNA expression. Failure of Caspase-6 response in tumor samples as compared to normal samples could suggest Caspase-6 as a candidate tumor suppressor gene in a subset of oral cancer.