Mutation Analysis of the Dimer Forming Domain of the Caspase 8 Gene in Oral Submucous Fibrosis and Squamous Cell Carcinomas

Background: Missense and frame-shift mutations within the dimer forming domain of the caspase 8 genehave been identified in several cancers. However, the genetic status of this region in precancerous lesions, likeoral submucous fibrosis (OSMF), and well differentiated oral squamous cell carcinomas (OSCCs) in patientsfrom southern region of India is not known, and hence the present study was designed to address this issue.Materials and
Methods: Genomic DNA isolated from biopsy tissues of thirty one oral submucous fibrosis andtwenty five OSCC samples were subjected to PCR amplification with intronic primers flanking exon 7 of thecaspase 8 gene. The PCR amplicons were subsequently subjected to direct sequencing to elucidate the status ofmutation.
Results: Sequence analysis identified a frame-shift and a novel missense mutation in two out of twentyfive OSCC samples. The frame-shift mutation was due to a two base pair deletion (c.1225_1226delTG), whilethe missense mutation was due to substitution of wild type cysteine residue with phenylalanine at codon 426(C426F). The missense mutation, however, was found to be heterozygous as the wild type C426C codon was alsopresent. None of the OSMF samples carried mutations.
Conclusions: The identification of mutations in OSCClesions but not OSMF suggests that dimer forming domain mutations in caspase 8 may be limited to malignantlesions. The absence of mutations in OSMF also suggests that the samples analyzed in the present study maynot have acquired transforming potential. To the best of our knowledge this is the first study to have exploredand identified frame-shift and novel missense mutations in OSCC tissue samples.