Identify the methylation level of genes in epithelial cells stimulated with arecoline, a main component of betel quid. Overall design: Human gingival epithelial progenitors were cultured and treated with a 3-day alternating regimen with/without 50 μg/ml arecoline for 1 month Please note that experiments were performed technically as dual channel (eg, Cy3 and Cy5-labeled samples hybridized to the same array) but the results were processed as though they are single channel (Cy3 and Cy5 signals are calculated; Cy3/Cy5 ratios are not calculated), and thus the 'Raw data.txt' file contains raw data for both Sample 1 (Control) and Sample 2 (Arecoline).