HIF1A and neoplasm: One explanation, albeit speculative, could be that HIF1a competent tumor cells, i.e., with a relatively high HIF1a expression, behave less aggressively under hypoxic conditions than HIF1 negative tumor cells, because they are still dependent on the blood supply from blood vessels and have not yet (fully) developed the capacity to survive under such circumstances.26–29 This could also explain the tendency observed toward better OS for patients with high expression of HIF1a (Fig. 2).