ZEB1 and cancer: Importantly, one of the critical oncogenic responses orchestrated by HIF1α is epithelial-to-mesenchymal transition (EMT) process [27–29] in which the cancer cells switch expression of markers of epithelial cells, such as E-cadherin to mesenchymal markers such as N-cadherin, vimentin, and transcription factors Snail1, Slug (Snail2), ZEB1, ZEB2 and Twist thereby facilitating the invasive migration and metastasis of cancer cells [28, 29].