Journal
CANCER RESEARCH
Volume 75, Issue 6, Pages 963-973Publisher
AMER ASSOC CANCER RESEARCH
DOI: 10.1158/0008-5472.CAN-14-1990
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Funding
- Israel Science Foundation [813/12, 1617/12]
- Israel Cancer Association [20110078]
- Israel Cancer Research Fund (Research Career Development Award)
- Israel Center of Research Excellence program (I-CORE, Gene Regulation in Complex Human Disease Center) [41/11]
- European Union Seventh Framework Program (FP7) [276890]
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Breast tumors are characterized by an extensive desmoplastic stroma, abundantly populated by fibroblasts. Cancer-associated fibroblasts (CAF) support tumorigenesis by stimulating angiogenesis, cancer cell proliferation, and invasion. CAF also orchestrate tumor-promoting inflammation in multiple tumor types, including breast cancer. However, the mechanisms through which normal tissue fibroblasts are reprogrammed to tumor-promoting CAFs are mainly obscure. Here, we show that mammary fibroblasts can be educated by breast cancer cells to become activated to a proinflammatory state that supports malignant progression. Proteomic analysis of breast cancer cell-secreted factors identified the secreted proinflammatory mediator osteopontin, which has been implicated in inflammation, tumor progression, and metastasis. Osteopontin was highly secreted by mouse and human breast cancer cells, and tumor cell-secreted osteopontin activated a CAF phenotypes in normal mammary fibroblasts in vitro and in vivo. Osteopontin was sufficient to induce fibroblast reprogramming and neutralizing antibodies against osteopontin-blocked fibroblast activation induced by tumor cells. The ability of secreted osteopontin to activate mammary fibroblasts relied upon its known receptors CD44 and alpha(V)beta(3) integrin. Strikingly, osteopontin silencing in tumor cells in vivo attenuated stromal activation and inhibited tumor growth. Our findings establish a critical functional role for paracrine signaling by tumor-derived osteopontin in reprograming normal fibroblasts into tumor-promoting CAFs. (C)2015 AACR.
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