Therapeutic activity of 3,3′-diindolylmethane on prostate cancer in an in vivo model

BACKGROUND. Prostate cancer (PC) is the second leading cancer-related death in men in Western countries. Hence, efficient anti-carcinogenic and therapeutic compounds against PC are badly needed. We have previously shown that 3,3'-diindolylmethane (DIM) has a suppressive effect on the growth of human breast and PC cell lines. The objective of this study was examination of the potential therapeutic effects of DIM in an in vivo model. METHODS. TRAMP-C2, a mouse PC cell line, was injected into the flank of male C57BL/6 mice. When tumors appeared, mice were injected intraperitoneally with either corn oil (vehicle) or DIM (2.5, 5, or 10 mg per kg body weight) 3-times a week, for 3 weeks, and tumor volumes were measured bi-weekly with calibermeters. Later, the tumors were removed, their final weights and volumes were measured, and tumor sections were tested for histological studies. RESULTS. DIM had a significant inhibitory effect, caused by diminished tumor growth. Histological examination of tumors from treated groups revealed apoptosis and decreased cell proliferation, compared with the controls. DIM didn't affect body weights or kidney and liver functioning. CONCLUSIONS. The inhibitory action of DIM on tumor growth was demonstrated in vivo. Hence, this compound at the concentrations tested may offer an effective and non toxic therapeutic means against tumor growth in rodents, and may serve as a potential natural anticarconigenic compound in humans. (C) 2004 Wiley-Liss, Inc.