Indole-3-Carbinol and 30,30-Diindolylmethane Modulate Androgen'sEffect onC-CChemokineLigand2andMonocyte Attraction to Prostate Cancer Cells

Inflammation has a role in prostate tumorigenesis. Recruitment of inflammatorymonocytes to the tumor site ismediated by C-C chemokine ligand 2 (CCL2) through binding to its receptor CCR2.We hypothesized that androgen could modulate CCL2 expression in hormone-responsive prostate cancer cells and thereby promote recruitment of monocytes. Given the inhibitory effect of broccoli-derived compounds indole-3carbinol (I3C) and 3,30-diindolylmethane (DIM) on androgen-dependent pathways, we also reasoned that I3C andDIM couldmodulate the effect of androgen onCCL2-mediated pathways. Dihydrotestosteronewas found to induce a time-dependent (0–72 hours) and concentration-dependent (0–1 nmol/L) increase in CCL2 mRNA levels in androgen-responsive human prostate cancer cells (LNCaP). This increase in CCL2 mRNA corresponded with increased secretion of CCL2 protein. The effect of dihydrotestosterone was mediated through an androgen receptor (AR)-dependent pathway as small inhibitor RNA against AR negated the induction of CCL2. Although dihydrotestosterone also induced TWIST1 mRNA, an epithelial– mesenchymal transition–related factor, and purported inducer of CCL2, blocking its expression with small inhibitor RNAdidnot inhibit dihydrotestosterone inductionofCCL2mRNA.Moreover, conditionedmedia fromandrogen-treated cells promotedhumanmonocyte THP-1 cellmigration and this effectwas blockedby antibody against CCL-2. Both I3C and DIM inhibited promotional effects of dihydrotestosterone on CCL2 and migration. These results show that androgen may regulate CCL2 and promote inflammatory microenvironment in prostate tumors and that this process can be blocked by broccoli-derived compounds. Cancer Prev Res; 6(6); 519–29. 2013 AACR.