Fig. 5

Quercetin strengthens t-AUCB-induced cell growth inhibition by inhibition of Hsp27 and COX-2. a: CCK-8 assay for cell viability. U87 and U251 cells were separately treated with vehicle control (DMSO), 5 μM, 15 μM, 30 μM, 60 μM quercetin, 200 μM t-AUCB, or 200 μM t-AUCB plus 15 μM, 30 μM or 60 μM quercetin for 48 h. The OD values represented the cell viability. Quercetin inhibits cell growth in concentration-depended manner since 15 μM, and strengthens t-AUCB induced cell growth inhibition. t-AUCB also strengthens quercetin-induced cell death (*P < 0.05, **P < 0.01). Q: Quercetin; t: t-AUCB. b: CCK-8 assay for cell viability. In U87 and U251 cells, knockdown of Hsp27 or COX-2 strengthens t-AUCB-induced cell growth inhibition (*P < 0.05, **P < 0.01). siHsp27: Hsp27 siRNA; siCOX-2: COX-2 siRNA; t: t-AUCB. c, d: Cell apoptosis analysis for U87 cells treated with vehicle control, 200 μM t-AUCB, 30 μM quercetin or 200 μM t-AUCB plus 30 μM quercetin for 48 h. Vehicle control treated cells the apoptosis proportion (Low Right and Upper Right section) was 4.51 ± 0.69 %. Cells treated with 200 μM t-AUCB exhibited no increase in apoptosis proportion of 5.62 ± 1.48 % (P > 0.05). Cells treated with 30 μM quercetin also exhibited no increase in apoptosis proportion of 6.35 ± 1.55 % (P > 0.05). For cells treated with 30 μM quercetin plus 200 μM t-AUCB, the apoptosis proportion was significantly increased into 16.38 ± 1.53 % (**P < 0.01). Q: Quercetin; t: t-AUCB. e: The caspase-3 activity assay for U87 cells treated with vehicle control, 200 μM t-AUCB, 30 μM quercetin or 200 μM t-AUCB plus 30 μM quercetin. OD value represented the caspase-3 activity (*P < 0.05, **P < 0.01). Q: Quercetin; t: t-AUCB