[Effect of 2-methoxyestradiol combined with quercetin on prostate cancer in vitro]

To detect the effects of quercetin (Que) combined with 2-methoxyestradiol (2-ME) on the proliferation of androgen-dependent LNCaP human prostate cancer cells line and androgen-independent PC-3 human prostate cancer cells line, and to evaluate the antitumor effects of different combos of the two drugs.

After LNCaP and PC-3 cells were treated with different concentration of quercetin (0, 3.125, 6.25, 12.5, 25, 50, 100, 200 μmol/L) or 2-ME (0, 0.312 5, 0.625, 1.25, 2.5, 5, 10 μmol/L) for 48 h, the inhibitory rates of cell growth were tested using trypan blue staining method respectively. Then the concentration-effect curves were drawn and IC(50) values were calculated. According to the fitted dose-effect curves and IC(50) values, appropriate concentrations of quercetin and 2-ME were selected to compose 16 different combos. Then cells were treated with different combos of Que and 2-ME for 48 h, and then the growth inhibitory rates of cell growth were detected. According to the equation and median-effect principle, the CI values of 16 different combos of Que and 2-ME were calculated to evaluate their antitumor effects.

The inhibition rate of LNCaP or PC-3 cell growth treated with varying doses of quercetin or 2-ME alone showed a dose-dependent increase respectively. The IC(50) values of quercetin and 2-ME were 23.29 μmol/L and 1.89 μmol/L for LNCaP cells; and 22.12 μmol/L and 1.74 μmol/L for PC-3 cells respectively. After treated with 16 combos of Que (5, 10, 20, 40 μmol/L) and 2-ME (0.5, 1, 3, 5 μmol/L) for 48 h, for LNCaP cells, lower dose of Que (5 and 10 μmol/L) with higher dose of 2-ME (3 and 5 μmol/L) showed synergistic activity, whereas for PC-3 cells, besides the above combination of Que 10 μmol/L and 2-ME 3 μmol/L, higher dose of quercetin (20 and 40 μmol/L) with higher dose of 2-ME (3 and 5 μmol/L) also showed synergistic activity.

Both quercetin and 2-methoxyestradiol could inhibit the growth of LNCaP and PC-3 human prostate cancer cells in a dose dependent manner. We confirmed that combinations of quercetin and 2-ME at appropriate concentrations have the potential for synergetic antiproliferative activity in vitro.