THBS1 and leukemia: Although an in vivo study examining the effects of whole body exposure to hypoxia on leukaemia progression reported no significant differences in blood cell counts or cellular proliferation or apoptosis rates of the control mice following daily 18 hour exposure to ~10% oxygen during 30 days, significantly increased levels of the anti-angiogenic factor, thrombospondin-1, have been observed in hypoxia-exposed endothelial cells [60,61].