SPP1 and cancer: Epithelial–mesenchymal transition (EMT) has been found to be mediated by SPP1, especially in its type 3 form (cancer metastases), through the upregulation of transcription factors such as TWIST [7,8], SNAIL1 [8] and SNAIL2 [8], as well as the activation of pathways such as PI3K-AKT-TWIST and hypoxia-inducible factor-1 alpha (HIF-1α) in various cancer models.