Normal breast fibroblasts (NBFs) support and maintain the architecture of the organ, and can also suppress tumorigenesis. However, the mechanisms involved are not fully understood. We have shown here that NBFs suppress breast carcinogenesis through secretion of osteoprotegerin (OPG), a soluble decoy receptor for the Receptor Activator of NF-κB ligand (RANKL). Indeed, NBFs and human recombinant OPG (rOPG), suppressed breast cancer cells proliferation and motility through inhibition of the epithelial-to-mesenchymal transition (EMT) process both in vitro and in vivo. Additionally, rOPG inhibited the IL-6/STAT3 and NF-κB pathways as well as the OPG gene, which turned out to be STAT3-regulated. This was confirmed using denosumab, a RANKL-targeted antibody, which also inhibited NF-κB, down-regulated OPG and repressed EMT in breast cancer cells grown in 2D and 3D. Importantly, both rOPG and denosumab targeted cancer stem cells (CSCs). This was mediated through inhibition of the CSC-related pathway β-catenin. Moreover, rOPG reduced tumor growth and inhibited breast CSC biomarkers in orthotopic humanized breast tumors. Therefore, normal mammary fibroblasts can suppress carcinogenesis through OPG, which constitutes great potential as preventive and/or therapeutic molecule for breast carcinomas.

正常的乳腺成纤维细胞 (NBF) 支持和维持器官的结构，还可以抑制肿瘤发生。然而，所涉及的机制尚不完全清楚。我们在这里表明，NBFs 通过分泌护骨素 (OPG) 来抑制乳腺癌的发生，OPG 是 NF-κB 配体 (RANKL) 受体激活剂的可溶性诱饵受体。事实上，NBF 和人重组 OPG (rOPG) 通过在体外和体内抑制上皮间质转化 (EMT) 过程来抑制乳腺癌细胞的增殖和运动。此外，rOPG 抑制 IL-6/STAT3 和 NF-κB 通路以及OPG基因，结果证明是 STAT3 调节的。使用地诺单抗（一种 RANKL 靶向抗体）证实了这一点，该抗体还抑制 NF-κB，下调 OPG 并抑制 2D 和 3D 生长的乳腺癌细胞中的 EMT。重要的是，rOPG 和地诺单抗都靶向癌症干细胞 (CSC)。这是通过抑制 CSC 相关通路 β-连环蛋白来介导的。此外，rOPG 可减少原位人源化乳腺肿瘤中的肿瘤生长并抑制乳腺 CSC 生物标志物。因此，正常乳腺成纤维细胞可以通过OPG抑制癌变，这构成了作为乳腺癌预防和/或治疗分子的巨大潜力。