RB1 and neoplasm: In contrast to the clear requirement for Hif1a in tumour formation in the autochthonous setting, we find that HIF-1α rather exhibits putative tumour suppressor activities in cell culture-based assays, including inducing the early loss of proliferative capacity of MEFs following Vhl deletion, inhibiting the proliferation of immortalised Vhl/Trp53 null MEFs and inhibiting anchorage independent growth of a Vhl/Trp53/Rb1 mutant mouse ccRCC cell line.