Another prospective study from the EPIC-Heidelberg cohort reported a U-shaped association between IGF-1 levels and mortality, with both low and high IGF-1 linked to increased risks of cancer (67).IGF-1 and its isoforms IGF-1Ea, IGF-1Eb, and IGF-1Ec play critical roles in breast cancer by promoting proliferation, epithelial-to-mesenchymal transition (EMT), and metastasis via IGF-1 receptor (IGF-1R)-mediated signaling pathways (68). This evidence concerns the gene IGF1 and breast cancer.