Growth inhibitory efficacy of lycopene and β-carotene against androgen-independent prostate tumor cells xenografted in nude mice

Scope: In this study, we evaluated the efficacy of lycopene against the growth of prostate cancer in vivo. Methods and results: Athymic nude mice were implanted subcutaneously with human androgen-independent prostate carcinoma PC-3 cells. They were supplemented with a low or a high dose of lycopene (4 and 16 mg/kg) and a single dose of beta-carotene (16 mg/kg) twice a week for 7 wk. At the end of the experiment, both lycopene and beta-carotene strongly inhibited the tumor growth, as evidenced by the decrease in tumor volume and tumor weight. High-dosage lycopene and beta-carotene significantly decreased the expression of proliferating cell nuclear antigen in tumor tissues and increased the levels of insulin-like growth factor-binding protein-3 in plasma. In addition, high-dosage lycopene supplementation significantly decreased the vascular endothelial growth factor (VEGF) levels in plasma. In contrast, beta-carotene supplementation significantly increased the VEGF levels, as compared with tumor control group. Conclusion: Lycopene and beta-carotene supplementation suppressed the growth of prostate tumor cells, and the effects are likely associated with reduction of proliferation (attenuation of proliferating cell nuclear antigen expression) and with interference of the insulin-like growth factor 1 signaling (increased plasma insulin-like growth factor-binding protein-3 levels). Furthermore, the inhibition of VEGF by lycopene suggests that the antitumor mechanisms of lycopene also involve anti-angiogenesis.