Chromosomal gains and losses indicate oncogene and tumor suppressor gene candidates in salivary gland tumors

The incidence of salivary gland tumor in Poland is growing in the last two decades. Simultaneously a progress in understanding the genetic mechanisms of formation of this tumor was achieved by detecting several genes like PLAG1 involved in its pathogenesis. In this study we perform a whole genome, CGH analysis with the aim to identify recurrent, chromosomal copy number changes possibly indicating novel tumor suppressor gene or oncogene loci. 29 salivary tumor samples: Cystadenolymphoma-warthin (15) and adenoma polymorphum (14) located in the parotid (27) and submandibular gland (2) were collected and CGH was performed. The established copy number profiles were compared in order to asses the smallest common region of gains and losses. The delineated regions were further analyzed with the UCSC Genome Browser on Human Mar. 2006 Assembly to asses their gene content. Altogether, salivary gland tumors presented a different aberration pattern than these reported for head and neck squamous cell carcinoma (HNSCC) but no significant differences were observed between Warthin and adenoma polymorphum tumors. Moreover, several potential tumor suppressor genes and oncogenes were identified in the smallest, common altered regions. We show a frequent deletion of the harakiri gene (12q24.2) in 12/29 tumors and TP53 gene (17p13.1) in 11/29 tumors as potential tumor suppressors in salivary gland cancers. Besides, we detected a frequent amplification of the 13q22.1-22.2 region in 13/29 cases harboring the KLF5 and KLF12 genes. KLF5 regulates the expression of survivin, an oncogene widely expressed in the majority of human cancers. The observed alterations may indicate important genetic events in the formation of salivary gland tumors. Especially the amplification in 13q may be a mechanism contributing to the expression of survivin and tumor progression.