TRAIL mRNA levels are markedly higher in normal oral epithelial cells (NOM) in comparison to immortalized (16B), premalignant (L1 and L2) and malignant oral epithelial cells (16BTu, 1386Tu, 686Tu, 101A, 1386Ln and 686Ln). Relative RNA expression levels of TRAIL were determined using Affymetrix U133A oligonucleotide microarrays. Signal intensity for TRAIL was calculated using the Affymetrix MAS 5.0 probe level algorithm. NOM: Normal oral epithelial cells; 16B: Normal oral epithelial cells immortalized by HPV-16 transfection (HOK-16B). L1: OPM cell line MSK-Leuk1; L2: OPM cell line MSK-Leuk2; 16BTu: tumorigenic cell line derived from HOK-16B; (HOK-16B-Bap-T); 1386Tu, 686Tu and 101A: Cell lines derived from primary OSCC. 1386Ln and 686Ln: Cell lines derived from synchronous lymph node metastases of 1386Tu and 686Tu tumors.