CpG Island Methylation Profiling in Human Salivary Gland Adenoid Cystic Carcinoma.
Achim H Bell, Diana Bell, Randal Weber, Adel K El-Naggar. University of Mississippi Medical Center, Jackson; University of Texas M.D. Anderson Cancer Center, Houston
Background: A better understanding of key molecular changes during the pathogenesis of salivary gland adenoid cystic carcinoma (ACC) could impact strategies to reduce recurrence and mortality from this cancer. Two epigenetic events involved in the pathogenesis of cancer are hypermethylation of tumor-suppressor gene promoters associated with transcriptional repression and hypomethylation associated with gene reexpression possibly linked to oncogene activation and genomic instability. The aim of this study was to identify genes (1) strongly deregulated by epigenetic CpG island methylation, (2) involved in development and survival of ACC.
Design: We analyzed 16 patients (tumor ACC and matching normal tissue) for aberrant hypermethylation using the methylated CpG island amplification and microarray (MCAM) method. For validation, CpG island regions of four genes, showing high changes in methylation with the MCAM method, were analyzed by Pyrosequencing.
Results: MCAM results for hyper- and hypomethylation show variable log 2 ratios between ACC and normal tissue: 1.3 to 2.3 fold increase in hypermethylation for 32 associated genes, and 1.3 to 1.5 fold changes in hypomethylation for seven associated genes. Strongest hypomethylations occur in gene regions near FBXO17 (catabolism, ubiquitination), PHKG1 (catabolism, phosphorylation), and cell surface proteins LOXL1, DOCK1 and PARVG. Strongest hypermethylations occur in regions around TSS of genes encoding predominantly transcription factors (EN1, FOXE1, GBX2, FOXL2, TBX4, MEIS1, LBX2, NR2F2, POU3F3, IRX3, TFAP2C, NKX2-4, PITX1, NKX2-5), except for 13 other genes with different functions (MT1H, EPHX3, AQPEP, BCL2L11, SLC35D3, S1PR5, PNLIPRP1, CLIC6, RASAL, XRN2, GSTM5, FNDC1, INSRR). Four CpG island regions, showing significant hypermethylation in MCAM, and associated with EN1, FOXE1, TBX4, and PITX1 were validated by Pyrosequencing. This method supported the MCAM results, with an average difference of 50% in CpG hypermethylation over all 4 gene regions investigated.
Conclusions: The genes associated with the highest CpG island hypermethylations in neoplastic tissue imply, that these genes are actively expressed in normal tissue and silenced in salivary gland ACC. To our knowledge, this is the first time that these genes have been implicated in salivary gland tumorigenesis.
Category: Head & Neck
Tuesday, March 1, 2011 8:00 AM
Platform Session: Section G, Tuesday Morning