As for TP, HIF-1α protein levels can be raised in tumours due to stimuli other than hypoxia: activation of oncogenes HER2 (Laughner et al, 2001), v-src (Jiang et al, 1997) and H-ras (Chen et al, 2001); loss of tumour suppressor gene function such as PTEN (Zundel et al, 2000) and signalling abnormalities such as MAPK (Richard et al, 1999). This evidence concerns the gene HRAS and neoplasm.