Although we did not specifically investigate the mechanisms of reoxygenation induced by BAY-87-2243, the observed rapid drop in hypoxia already after 3 days of treatment with unchanged tumor vascular area and perfused functional vessels may suggest a cytotoxic effect of BAY-87-2243 on hypoxic tumor cells, e.g. blockage of HIF-1-mediated hypoxia tolerance [28]. The gene discussed is HIF1A; the disease is neoplasm.