Abstract
Transforming growth factor beta (TGF-β) readily suppresses the development of early-stage breast cancers, an activity that gives way to tumor promotion in their late-stage counterparts. The molecular mechanisms underlying this mysterious switch in TGF-β function remain murky. In addressing this conundrum, Xu et al. observed aberrant 14-3-3ζ expression to prevent the formation of tumor-suppressive Smad2/3:p53 complexes, while simultaneously driving the generation of oncogenic Smad2/3:Gli2 complexes. Once formed, Smad2/3:Gli2 complexes stimulate the expression of parathyroid hormone-related protein necessary for breast cancer metastasis to bone. This viewpoint highlights 14-3-3ζ as an essential driver of oncogenic signaling by Smad2/3 and TGF-β in metastatic breast cancers.