Apoptotic activity by flow cytometry. (A) Flow cytometric analysis of apoptosis. (B) Percentages of apoptotic cells before and after UVB irradiation. With no irradiation, both p21 overexpression (p21+) and p21 silencing (p21–) had a pro-apoptotic effect, but p21 silencing showed a more profound pro-apoptotic effect than p21 overexpression. After UVB irradiation, apoptosis increased in all irradiated groups. In contrast to non-irradiated p21-overexpressing (p21+) cells, p21 overexpression in irradiated p21-overexpressing (UVB-p21+) cells displayed an anti-apoptotic effect. * p<0.05 vs. CON, #
p<0.05 vs. p21+, @
p<0.05 vs. p21–, &
p<0.05 vs. UVB-CON.