In vitro studies revealed that incubation of tumor cell cultures (SH-SY5Y, MCF-7) with 50–400 μM isatin decreased expression of the studied genes and their protein products, including Bcl-2, VEGF, cyclin D1, metalloproteinases 2 and 9 (MMP-2, MMP-9), monoamine oxidase A, HIF-1α (hypoxia-inducible factor 1-alpha), CXCR4 (chemokine receptor type 4) (Hou et al., 2008; Song et al., 2013; Ma et al., 2014; Xu et al., 2016; Sun et al., 2017). The gene discussed is HIF1A; the disease is neoplasm.