Fig. 2From: DNA hypermethylation of sirtuin 1 (SIRT1) caused by betel quid chewing—a possible predictive biomarker for malignant transformationFlow chart of cell culture. Human gingival epithelium progenitors (HGEPs), cells were treated with arecoline at a concentration of 50 μg/mL. The culture media was replaced every 3 days, alternating media with and without arecoline for 30 days. Untreated samples were used as controls. DDW, double-distilled water; ARE, arecolineBack to article page