For genomewide monitoring and identification of biomarkers of head and neck squamous cell carcinoma (HNSCC), we have conducted a systematic characterization of gene expression profiles, using human cDNA microarrays containing 9K clones, in 25 HNSCC cell lines and 1 immortalized human oral keratinocyte cell line. We used normal human oral keratinocytes (NHOKs) as a reference. Our study showed that genes primarily involved in cell cycle regulation, oncogenesis, cell proliferation, differentiation, apoptosis and cell adhesion were widely altered in the 26 cell lines. Upregulated genes included known oncogenes, protein kinases, DNA-binding proteins and cell cycle regulators, while those commonly downregulated included differentiation markers, cell adhesion proteins, extracellular matrix proteins, structural proteins (keratins) and protease inhibitor proteins. Compared to NHOK, we observed a striking reduction in the expression of genes involved in terminal differentiation, suggesting that a loss in this process is an important signature of HNSCC.
Key words: microarrays; head and neck squamous cell carcinoma; gene expression; tumor progression; oral cancer; biomarkers; differentiationHead and neck cancers represent the 6th most common human neoplasm in the developed world, resulting in 13,000 deaths each year in the United States alone, and amount to 5% of all newly diagnosed cancer cases in Northern and Western European countries. 1-3 More than 90% of this cancer type are of squamous origin and common sites include hypopharynx, larynx, oral cavity, nasopharynx, oropharynx, paranasal sinus, nasal cavity, parathyroid and salivary glands. 4 Despite recent advances in treatment, the long-term survival rate of head and neck squamous cell carcinoma (HNSCC) patients has remained at 50% with high rates of associated mortality. 5 Late presentation of lesions, lack of suitable markers for early detection and failure of advanced lesions to respond to available chemotherapy contribute to a poor outcome of HNSCC. The poor prognosis of HNSCC patients may also be a reflection of the fact that, while the major risk factors involved in HNSCC pathogenesis, such as alcohol and tobacco, are well recognized, 6 little is known on the molecular mechanisms underlying this type of cancer.The development of HNSCC is a multistep process accompanied by genetic and epigenetic changes, including loss of heterozygosity, gene inactivation by methylation and gene amplification, all of which can alter gene expression. 7 For instance, the most frequent cytogenetic alterations in HNSCC are gains of 3q, 8q, 20q, 7p, 11q13 and 5p and losses in 3p, 9p, 21q, 5q, 13q, 18q and 8p. 8 In these loci, there are genes that encode specific functional classes of proteins such as cell cycle regulators, tumor suppressors, cell adhesion molecules including integrin, and protein kinases. 9 -11 Furthermore, a role for Epstein-Barr virus (EBV) and human papillomavirus (HPV) 16 and 18 in certain HNSCC lesions has been reported. 12 For instance, EBV is now known to play ...
