More importantly, ephrin-A1 protein was also detected positively and increased significantly in the supernatants from hypoxia groups, the level of which was much higher in comparison with the normoxia groups (Figure 5B) (Figure S7C, D), suggesting that cancer cells may also secrete soluble form of ephrin-A1 in tumor hypoxic microenvironment. The gene discussed is EFNA1; the disease is cancer.