It is shown by a host of medical papers that the H2O2 produced acts as a second messenger molecule in human cells, promoting cells at several stages of the life history of tumor formation, starting from immortalization (loss of cell cycle arrest), to the EMT, tumor angiogenesis, activation of HIF1alpha leading to a hypoxia-like metabolic transition of the cells, and finally to invasiveness and the potential to metastasize (13, 16–18). The gene discussed is HIF1A; the disease is neoplasm.