MTT assay

AGS cells were seeded into 96-well plates at a density of 1.0 × 10³ cells/well and treated with different concentrations of RGP for 0 h, 12 h, 24 h, and 48 h. After the treatment, the cells were assessed for their proliferation ability using the MTT assay (Trevigen, MC, USA). Briefly, MTT solution (5 mg/L) was added to each well, and the cells were incubated for an additional 4 h. The medium containing the MTT solution was then carefully removed, and 100 μL of DMSO was added to each well. After 15 min, the relative absorbance at 570 nm was measured using a microplate spectrophotometer (Agilent Technologies, Cernusco sul Naviglio [MI], Italy).