Curcumin sensitizes TRAIL-resistant LNCaP xenografts. (A), LNCaP cells were injected into the right flanks of Balb c nude mice. After tumor formation (about 100 mm3), mice were treated with saline, curcumin (30 mg/kg, three days per week), TRAIL (15 mg/kg, four times during first three weeks) or curcumin and TRAIL. Tumor volume was calculated weekly. Data represent mean ± SE. (B), Effects of curcumin and/TRAIL on apoptosis (TUNEL staining) and cell proliferation (PCNA and Ki67 staining). Immunohistochemistry was performed to measure apoptosis (TUNEL assay), and expression of PCNA and Ki67 in tumor tissues derived from control and treated mice on week 6. (C), Quantification of TUNEL, PCNA and Ki67 positive tumor cells. Tumor slides of different treatment groups were visualized under microscope, and TUNEL, PCNA and Ki67 positive cells were quantified. Data represent mean ± SE. a1, a2; b1, b2 and c1, c2 are significantly different from their respective controls or TRAIL treated group (P < 0.05).