Effects of toll-like receptor 7 agonist imiquimod on the viability of SGC-7901 cells. Data are presented as mean ± standard deviation. aP<0.05 vs. 72 h, bP<0.05 vs. 48 h, cP<0.05 vs. 24 h. P-values were obtained from comparisons between tissues treated with 6.25, 12.5, 25, 50 and 100 µg/ml imiquimod for the same treatment duration.