Quercetin induce apoptosis in MCL. (A) MTS assay (left panel) and trypan blue exclusion test (right panel) were performed to assess the biologic effects of quercetin on MCL cell lines. All 3 cell lines showed a dose-dependent decrease in cell growth with quercetin treatment. Negative controls in all experiments were treated with the highest volume of DMSO used in the treated group. Results from the treated group are normalized to those of the negative controls. (B) Cell-cycle analysis by flow cytometry was performed using Mino cells with or without quercetin treatment. M1 represents the G_o/G₁ phase; M2, the S phase; M3/4, the G₂/M phase; and M5, the subG₀ apoptotic cell population. Compared with cells with quercetin treatment, treated cells showed a decrease in the proportion of cells in the S phase as well as the G₂/M phase. In addition, there was a dramatic increase in the size of the subG₀ cell population, in keeping with the occurrence of apoptosis. (C) All 3 MCL cell lines showed dose-dependent down-regulation of cyclin D1 after quercetin treatment at 24 hours. Negative controls were treated with DMSO in the same volumes used in the treatment group. (D) All 3 MCL cell lines showed dose-dependent down-regulation of Bcl-2 and Bcl-XL after quercetin treatment at 24 hours. Negative controls were treated with DMSO in the same volumes used in the treatment group. (E) All 3 MCL cell lines showed expression of cleaved caspases-3, -7, and -9, as well as PARP, after quercetin treatment at 24 hours. Negative controls were treated with DMSO in the same volumes used in the treatment group. Error bars indicate SD.