The first observations were made almost exclusively on tumor cell lines—it was found that melatonin lowers the level of HIF-1α, e.g., in gliomas (Zhang et al., 2013), colon cancer cells (HCT116) (Park et al., 2009), and pancreatic cancer cells (PANC-1) (Dai et al., 2008). The gene discussed is HIF1A; the disease is neoplasm.