Metformin suppresses HIF‐1α expression in cancer‐associated fibroblasts to prevent tumor‐stromal cross talk in breast cancer
Shan Shao, Lin Zhao, Gaili An, Lingxiao Zhang, Xin Jing, Minna Luo, Wei Li, Meng Du, Qian Ning, Xinhan Zhao, Jianjun Lei
Abstract
The tumor microenvironment (TME) is a crucial factor in cancer progression. In breast cancer, cancer-associated fibroblasts (CAFs) and the derived stromal components have been recognized as comprising the majority of the pathological structure of the TME. In this study, we show that metformin (Met), a diabetes drug, transforms CAFs in the TME. Met disrupts tumor-stromal cross talk by preventing breast cancer cell transforming growth factor-β (TGF-β) signaling and the production of stromal-derived factor-1 (SDF-1) and interleukin-8 (IL-8) by CAFs. The suppression of bidirectional signaling between tumor cells and CAFs by Met is attributed to increased phospho-AMP kinase (p-AMPK) levels. By upregulating p-AMPK in CAFs, Met induces prolyl hydroxylases (PHDs), leading to the degradation of hypoxia-inducible factor-1α (HIF-1α) in CAFs. Moreover, interruption of HIF-1α-driven SDF-1 signaling in CAFs by Met leads to decreased breast cancer cell invasion. These findings suggest that Met may be used to target tumor-promoting signaling between CAFs and breast cancer cells in the TME.