Modulation of breast cancer development in MMTV-PyVT mice by adiponectin: a perspective on tumor microenvironment

Abstract

BACKGROUND: The survival and growth of epithelial carcinoma cells are critically dependent on the interactions with the neighboring stromal cells. Adiponectin, a molecule exclusively produced by adipose tissue, possesses potent anti-inflammatory and anti-tumorigenic activities. Its expression and production are inversely associated with breast cancer risks in pre- and post-menopausal women. Reduced or completely loss of adiponectin expression enhances the development of mammary tumors in MMTV-PyVT mice. Despite these evidences, the mechanisms underlying the anti-breast cancer activity of adiponectin remain poorly understood. METHODS: Adiponectin-deficient MMTV-PyVT mice that show distinct basal epithelial-like features of mammary tumors are used for analyzing the stromal vascular fractions (SVF) of the adipose tissues in tumor microenvironment. RESULTS: Flow cytometric analyses demonstrate that adiponectin deficiency significantly alters the composition of cells in SVF isolated from the mammary adipose tissues. Adiponectin-deficient SVF contribute to the metaplastic features of the basal epithelial-like breast cancers. Co-implantation of SVF derived from adiponectin-deficient mice accelerates mammary tumor development and metastasis in NOD/SCID mice engrafted with MDA-MB-231 human breast cancer cells. Fluorescence Activated Cell Sorting isolates a population of CD44+CD25-CD100+ cells that are enriched in both thymus and SVF of mice lacking the expression of adiponectin. Upregulated CD100 expression interrupts early T-cell development and maturation. In mammary tissues, CD44+CD25-CD100+ cells facilitate the development of metaplastic basal epithelial-like breast cancers. Adiponectin treatment down-regulates CD100 expression, in turn enhancing Notch signaling and T-cell maturation in the thymus, and reduces the accumulation of CD44+CD25-CD100+ cells in the tumor microenvironment. CONCLUSIONS: These results support a pivotal role of adiponectin in mediating the epithelial-stroma crosstalk to prevent mammary carcinogenesis and shed new lights on the development of immuno-therapeutics for breast cancer diseases.