DOES THE PRESENCE OF THE HYPOXIA INDUCIBLE A SUBUNIT OF HIF-I FAVORS TUMOR-GROWTH OR TUMOR ASPHYXIA

HIF-1 is a transcription factor which stimulates the expression of sev eral genes induced by hypoxia, such as the gene encoding the vascular endothelial growth factor VEGF. Three papers report the effects of the inactivation of the HIF-1 alpha gene. The absence of HIf-1 alpha impa irs morphogenesis of the vascular tree, both in the embryo and in tera tocarcinomas obtained after injection of ES cells HIF-1 alpha -/- embr yos do not survive beyond midgestation. In contrast, one paper reports tumor growth inhibition, and another one its stimulation. These resul ts suggest that the role of HIF-1 in the hypoxic response is dependent on the genetic background.