Abstract 3263: Dietary supplement 3, 3’-diindolylmethane (DIM) as an antiangiogenic agent in breast cancer

Tumor angiogenesis refers to the sprouting and cooption of proliferating endothelial cells (EC’s) from adjacent pre-existing host vasculature, and is a key target of cancer therapy. Tumor cells exploit their microenvironment by releasing cytokines and growth factors to promote and support angiogenesis. Within this complex tumor microenvironment, we and others have shown that tumors can recruit bone marrow derived endothelial progenitor cells that differentiate into mature bone marrow-derived endothelial cells and incorporate into sprouting tumor neovessels. Under pathological circumstances, such as breast cancer, a clear association between estrogen receptor expression by EC’s, angiogenic activity, and/or tumor invasiveness has been made. Approximately, 80% of breast cancers are hormone-receptor-positive cancers, thus enabling tamoxifen as the mainstay of breast cancer therapy. The roles of the anti-estrogens fulvestrant (ICI) and the dietary supplement 3, 3’-diindolylmethane (DIM) on cell-cell interaction and angiogenesis have not been fully elucidated. This study is designed to evaluate and compare the effect of these antiestrogens on angiogenesis at the cellular and molecular levels using tube formation of human umbilical vein endothelial cells (HUVEC) as an in vitro angiogenesis model. HUVEC cells were treated with serial dilutions of either DIM or ICI in presence and absence of (3nM) estrogen, and subjected to in vitro tube formation, proliferation, migration, and angiogenesis antibody array assays. We report that HUVEC cells are more sensitive to DIM than ICI. At 25 μM concentration, DIM significantly inhibited the crucial steps of angiogenesis including HUVEC cells proliferation, migration, cytokine release, and tube formation in an estrogen independent manner. On the other hand, at 1 μM concentration, ICI significantly exerted an antiangiogenic effects inhibiting HUVEC cells proliferation, migration, and tube formation, but this effect was totally dependent on the presence of estrogen. These results are validated by our observation that HUVEC cells express estrogen receptor beta (ER-β) and not estrogen receptor alpha (ER-α). A correlative effect between the antiangiogenic activity of DIM and ER-β upregulation was noted. We believe that the anti-estrogenic activity of DIM is mediated through the genomic and non-genomic activity of ER-β in endothelial cells predicting a new target for DIM to manifest its antiangiogenic effect. Citation Format: Ghada