Fig. 2. The pivotal role of HIF-1 in tumour survival and aggressiveness. HIF-1 is a transcription factor which induces the transcription a large set of genes, the hypoxia response elements (HRE). Some of them are summarized in this figure. One can divide the HRE in four different classes, and representative examples are depicted herein. (i) HRE promoting metabolic switches (orange); (ii) HRE promoting CSCs formation and self-renewal (pink); (iii) HRE promoting changes in the extra cellular matrix (ECM) (green); and (iv) HRE promoting the epithelial mesenchymal transition (EMT) (blue).