Genetic expression profiling of parotid neoplasms by cDNA microarrays

Differentially expressed genes in various benign and malignant salivary gland tumours were identified by use of cDNA microarrays containing 19,000 human expressed sequence tags. Samples were derived from 5 patients with pleomorphic adenoma, 4 with Warthin’s tumour, one with clear cell carcinoma, and 2 with mucoepidermoid carcinoma. Tumours were classified by using a subset of 486 genes. Benign Warthin’s tumour and pleomorphic adenoma showed very distinctive gene expression patterns. A total of 133 genes differentiated the single malignant clear cell carcinoma from non-tumour salivary glands (p < 0.01), whereas only 16 genes separated it from the highly related benign pleomorphic adenoma (p < 0.01). A total of 57 cDNAs were associated with mucoepidermoid carcinoma (p < 0.01). The results show gene expression alterations common to all tumours and unique to each benign and malignant tumour. The numerous Expressed Sequence Tags of unknown function we identified could also become useful as tumour markers and represent a set of novel tumour-associated genes.