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PDF file - 140K, Vessel stabilization

PDF file - 156K

PDF file - 139, ER� is efficiently suppressed in BM and BM-derived cells using chimeric hematopoietic approach

PDF file - 364K, B16K1, LL2 and 4T1 characterization

PDF file - 162K, Vessel diameter quantification by granulometry

PDF file - 122K, B16K1 time- and size-dependent tumor harvesting

Estrogens directly promote the growth of breast cancers that express the estrogen receptor α (ERα). However, the contribution of stromal expression of ERα in the tumor microenvironment to the protumoral effects of estrogen has never been explored. In this study, we evaluated the molecular and cellular mechanisms by which 17β-estradiol (E2) impacts the microenvironment and modulates tumor development of ERα-negative tumors. Using different mouse models of ER-negative cancer cells grafted subcutaneously into syngeneic ovariectomized immunocompetent mice, we found that E2 potentiates tumor growth, increases intratumoral vessel density, and modifies tumor vasculature into a more regularly organized structure, thereby improving vessel stabilization to prevent tumor hypoxia and necrosis. These E2-induced effects were completely abrogated in ERα-deficient mice, showing a critical role of host ERα. Notably, E2 did not accelerate tumor growth when ERα was deficient in Tie2-positive cells, even in mice grafted with wild-type bone marrow. These results were extended by clinical evidence of ERα-positive stromal cell labeling in the microenvironment of human breast cancers. Together, our findings therefore show that E2 promotes the growth of ERα-negative cancer cells through the activation of stromal ERα (extra-hematopoietic Tie-2 positive cells), which normalizes tumor angiogenesis and allows an adaptation of blood supply to tumors, thereby preventing hypoxia and necrosis. These findings significantly deepen mechanistic insights into the impact of E2 on tumor development with potential consequences for cancer treatment. Cancer Res; 72(12); 3010–9. ©2012 AACR.

PDF file - 204K, B16K1 Tumor necrosis in C57BL/6 mice