Research section Indole-3-carbinol and 3,3 0 -diindolylmethane induce apoptosis in human prostate cancer cells M. Nachshon-Kedmi a , S. Yannai a, *, A. Haj b , F.A. Fares b a Faculty of Food Engineering and Biotechnology, Technion— Israel Institute of Technology, Haifa 32000, Israel b Department of Biochemistry and Molecular Genetics, Carmel Medical Center, Haifa, Israel Accepted 6 December 2002 Abstract Cruciferous vegetables contain glucobrassicin which, during metabolism, yields indole-3-carbinol (I3C). In a low pH environment I3C is converted into polymeric products, among which 3,3 0 -diindolylmethane (DIM) is the main one. The apoptotic effects of I3C and DIM were exhibited in human breast cancer cells. The objectives of this study were: (a) examination of the potential effects of I3C and DIM on the proliferation and induction of apoptosis in human prostate cancer cell lines with different p53 status; (b) to try to characterise the mechanism(s) involved in these effects. Our results indicate that both indole derivatives suppress the growth of these cells in a dose- and time-dependent manner, by inducing apoptosis. It appears that these indolic compounds may offer effec- tive means against prostate cancer. Induction of apoptosis was p53-independent. Moreover, the indole derivatives employed did not affect the levels of bcl-2, bax and fasL. # 2003 Elsevier Science Ltd. All rights reserved. Keywords: Apoptosis; Diindolylmethane; Indole-3-carbinol; Prostate cancer 1. Introduction Epidemiological studies have shown that diets rich in fruits and vegetables and low in fat and proteins are associated with a lower risk of cancer (Dragsted et al., 1993; Tavani and Vecchia, 1995). A number of studies have demonstrated a decreased incidence of various cancers (including prostate cancer) in humans consum- ing large amounts of cruciferous vegetables, such as broccoli, Brussels sprouts, cabbage and cauliflower (Cohen et al., 2000). These vegetables contain gluco- brassicin, which undergoes hydrolysis by myrosinase upon crushing, or by cooking (Bradfield and Bjeldanes, 1987; Verhoeven et al., 1997). The main hydrolysis pro- duct of glucobrassicin is indole-3-carbinol (I3C). In a low pH environment, I3C is converted into many poly- meric products, among which 3,3 0 -diindolylmethane (DIM) is the main one (Fenwick et al., 1982; Bradfield and Bjeldanes, 1987). It was shown that these products have apoptotic properties. The apoptotic effect of I3C and DIM has been demonstrated in human breast can- cer cells. I3C suppressed MCF-7 cell growth, in part by induction of apoptosis (programmed cell death), which was independent of p53 and bax expression. It may also be due to its conversion into a more potent compound, DIM (Fares et al., 1998; Ge et al., 1996, 1999). Animal studies have shown that mice and rats fed indolic com- pounds had a significantly lower incidence of both car- cinogen-induced (Wattenberg and Loub, 1978; Srivastava and Shukla 1998) and spontaneous tumours (Bradlow et al., 1991; Kojima et al., 1994), and the time intervals for the appearance of cancer was longer. Recently it has been reported that I3C inhibits the proliferation of PC3, a poorly differentiated human prostate cancer cell line. Induction of G 1 cell cycle arrest, leading to apoptosis, was also observed in those cells, treated with 30–100 mm of I3C (Chinni et al., 2001). Prostate cancer is the most common diagnosed malignancy (accounting for 29% of the newly diagnosed cancers) and the second leading cause of male death in Western industrialized countries (Tang and Porter, 0278-6915/03/$ - see front matter # 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0278-6915(03)00004-8 Food and Chemical Toxicology 41 (2003) 745–752 www.elsevier.com/locate/foodchemtox Abbreviations: DIM, 3,3 0 -diindolylmethane; FCS, fetal calf serum; I3C, indole-3-carbinol; LDH, lactate dehydrogenase; PARP, poly ADP-ribose polymerase. * Corresponding author. Tel.: +972-4-829-3350; fax: +972-4-832- 0742.