Effects of α-santalol on p21 and p53 in A431 cells. (A). Protein levels of p21 and p53 after α-santalol treatment in A431 cells were evaluated by Western blotting. (B). Cell cycle distribution in p21 siRNA transfected A431 cells was analyzed by flow cytometer. Data were summarized and presented as the mean ± SD of three observations. For each p21 siRNA transfection in A431 cells, Western blotting was performed to ensure the inhibition of p21 protein expression.