Resveratrol suppresses the proliferation of drug-resistant MM cell lines and potentiates the apoptotic effect of bortezomib and thalidomide. (A-D) U266 cells (5 × 103/100 μL; A), dexamethasone-sensitive (B, left) and dexamethasone-resistant (B, right) MM.1 cells (20 × 103/100 μL), doxorubicin-sensitive (C, left) and doxorubicin-resistant (C, right) RPMI 8266 cells (20 × 103/100 μL), and melphalan-sensitive (D, left) and melphalan-resistant (D, right) RPMI 8266 cells were plated in triplicate, treated with 50 μM resveratrol, and then subjected to MTT assay on days 2, 4, or 6 to analyze proliferation of cells. ○ represents control and ● represents resveratrol-treated cells. Each point on line is an average of triplicate value. Resveratrol induced inhibition of cell growth at days 2 and 4 was statistically significant (P < .05). (E-F) U266 cells (1 × 106/mL) were treated with 25 μM resveratrol and 20 nM bortezomib (E) or 10 μg/mL thalidomide (F) alone or in combination for 24 hours at 37°C. Cells were stained with a live/dead assay reagent for 30 minutes and then analyzed under a fluorescence microscope as described in “Materials and methods.” Percentage of apoptosis is indicated in the inset. (G) U266 cells (1 × 106/mL) were treated with 25 μM resveratrol, 20 nM bortezomib (left), or 10 μg/mL thalidomide (right) alone or in combination for 24 hours at 37°C. Cells were incubated with anti-annexin V antibody conjugated with FITC and then analyzed with a flow cytometer for early apoptotic effects. The results shown are representative of 3 independent experiments. *Values significantly (P < .05) different from control as well as single agent. Error bars represent SD of triplicate values.
