VEGFA and neoplasm: Hypoxia is also a characteristic feature of tumor development because tumor vasculature differs from that seen in healthy tissues in that (1) tumor-derived ECs display higher levels of glycolysis and VEGF secretion than normal ECs [27], (2) tumor vessels have a smaller or more compressed lumen, (3) the vessel wall is abnormal with loosely attached mural cells, (4) the ECM is irregular, and (5) the ECs are poorly connected.