Abstract
Objectives:
Aquaporin-1 (AQP1) is a candidate oncogene that is epigenetically modified in adenoid cystic carcinoma (ACC). We sought to 1) assess AQP1 promoter methylation and gene expression in an ACC cohort, 2) identify correlations between AQP1 and clinical outcomes, and 3) explore the role of AQP1 in tumor progression in vitro.
Methods:
DNA and RNA were isolated from ACC tumors and control salivary gland tissues. Quantitative methylation-specific polymerase chain reaction (PCR) was performed on bisulfite-treated DNA. Quantitative reverse transcription PCR was performed after cDNA synthesis. Retrospective chart review was performed for collection of demographic information and clinical outcomes. Cell lines stably over-expressing an AQP1 plasmid or empty vector were generated. Cell scratch and Matrigel invasion assays were then performed.
Results:
Methylation results from 77 ACC tumors and 30 controls demonstrated that AQP1 was hypomethylated in tumors (P < 0.0001). Fifty-eight tumors (75.3%) displayed AQP1 hypomethylation compared to controls. AQP1 expression was assessed in 58 tumors and 23 controls, and a trend towards increased expression in tumors was found (P = 0.08). Statistical analysis revealed no associations between AQP1 methylation status and clinical outcomes. However, increased AQP1 expression was associated with improved overall survival and longer time to metastasis (P < 0.05). AQP1 over-expression in vitro did not affect cell migratory or invasive capacities in cell scratch and invasion assays.
Conclusions:
AQP1 hypomethylation is common in ACC, and AQP1 tends to be over-expressed in these tumors. Increased AQP1 expression is associated with improved prognosis. Further in vitro studies are necessary to clarify the role of AQP1 in ACC progression.
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