Figure 12. Combined treatment of CAPE with PI3K inhibitor LY294002 or BCl-2 inhibitor ABT737 showed additive and mild synergistic inhibition on proliferation of LNCaP 104-R1 cells.

Proliferation of LNCaP 104-R1 cells treated with increasing dosage (0, 5, 10, 20 μM) of LY294002 (A), combination of CAPE and LY294002 (B), ABT737 (D), and combination of CAPE with ABT737 (E) was determined by 96-well proliferation assay. The ration of expected cell number/observed cell number of LNCaP 104-R1 cells treated with combination of CAPE and LY294002 (C) or combination of CAPE and ABT737 (F) was shown. The effect of the combined treatment was determined by the ratio of expected cell number/observed cell number. For example, treatment of 104-R1 cells with 5 μM of ABT737 decreased the cell number to 69.2% and treatment with 104-R1 cells with 5 μM CAPE alone decreased the cell number to 75.6%. The expected cell number of treatment combining 5 μM of ABT737 with 5 μM CAPE was 0.692 × 0.756 = 52.3%. The actual observed cell number is 47.0%. The ratio of expected cell number/observed cell number is 0.523/0.470 = 1.1. Ratio larger than one represents synergy of growth inhibition as the combined treatment of two drugs suppressed more cells than either drug alone. If the observed cell number is less than the cell number being treated with any one of the drug alone, this indicates additive suppressive effect of the combination treatment of the two drugs. For example, treatment of 104-R1 cells with 2.5 μM of LY294002 decreased the cell number to 91.2%, while treatment with 104-R1 cells with 40 μM CAPE decreased the cell number to 14.5%. The combination of 2.5 μM of LY294002 with 40 μM CAPE decreased the cell number to 13.1%, then we called the combination of 2.5 μM of LY294002 with 40 μM CAPE exhibited additive suppressive effects on LNCaP 104-R1 cells.