Microenvironment and Immunology Tamoxifen, Flaxseed, and the Lignan Enterolactone Increase Stroma- and Cancer Cell–Derived IL-1Ra and Decrease Tumor Angiogenesis in Estrogen-Dependent Breast Cancer

The proinflammatory cytokines IL-1a and IL-1b promote tumor angiogenesis that might be counteracted by the IL-1 receptor antagonist (IL-1Ra), anakinra, a clinically approved agent. A diet with high amounts of phytoestrogens, such as flaxseed (Flax), genistein (GEN), and the mammalian lignan enterolactone (ENL), may affect breast cancer progression in a similar fashion as the antiestrogen tamoxifen. Both cancer cells and tumor stroma may be targets for cancer therapy. By using microdialysis in a model of human breast cancers in nude mice, we could perform species-specific analyses of released proteins in the microenvironment. We show that tumors treated with tamoxifen and fed Flax or ENL exhibited decreased in vivo release of IL-1b derived from the murine stroma and decreased microvessel density whereas dietary GEN had no effects. Cancer cell–released IL1Ra were approximately 5 times higher than stroma-derived IL-1Ra. Tamoxifen, Flax, and ENL increased IL-1Ra levels significantly whereas GEN did not. The tumor stroma contained macrophages, which expressed the estrogen receptor. In vitro, estradiol decreased IL-1Ra released from breast cancer cells and from cultured macrophages. IL-1Ra decreased endothelial cell proliferation significantly in vitro whereas breast cancer cell proliferation was unaffected in presence of estradiol. Finally, IL-1Ra therapy of tumor-bearing mice opposed estrogen-dependent breast cancer growth and decreased angiogenesis. We conclude that the release of IL-1s both by cancer cells and the stroma, where macrophages are a key component, may offer feasible targets for antiestrogen therapy and dietary interventions against breast cancer. Cancer Res; 71(1); 51–60. 2011 AACR.