Although several oncogenes and tumor suppressor genes have been suggested to be of relevance for the development of
oral cancer, it is likely that additional genes are involved in this complex process. Therefore, in an attempt to isolate such genes, the aim of this study was to investigate changes in gene expression in human buccal
carcinoma cells as compared to normal buccal epithelial cells, and identify
mRNA overexpressed in the
carcinoma cell line. The method of differential display of
mRNA was used to isolate differentially expressed genes (Liang P et al, Science 257:967-971, 1992). A key step of this method, a polymerase chain reaction amplification, was optimized in terms of choice of thermostable
DNA polymerase, annealing temperature, molar ratios and concentrations of primers. The comparative analysis of expression in
tumor and normal buccal epithelial cells led to the isolation of three different mRNAs overexpressed in human oral
carcinoma cells, as confirmed by Northern blot analysis. Cloning and sequence analysis revealed that these genes, which were termed OTEX as in Oral
Tumor EXpressed, included a novel, previously not characterized, human gene, OTEX-1. OTEX-2 was identical to the gene coding for the L26
ribosomal protein, a
protein known to be overexpressed also in other
tumor cell types. OTEX-3 showed a perfect match to a sequence isolated during the human genome sequencing project, with a hitherto unknown function.