Lysine-specific demethylase 4A is an enzyme that in humans is encoded by the KDM4A gene. This gene is a member of the Jumonji domain 2 (JMJD2) family and encodes a protein with a JmjN domain, a JmjC domain, a JD2H domain, two TUDOR domains, and two PHD-type zinc fingers. This nuclear protein belongs to the alpha-ketoglutarate-dependent hydroxylase superfamily. It functions as a trimethylation-specific demethylase, converting specific trimethylated histone on histone H3 lysine 9 and 36 residues to the dimethylated form and lysine 9 dimethylated residues to monomethyl, and as a transcriptional repressor. Alterations in this gene have been found associated with chromosomal instability that leads to cancer. In humans, the role of Kdm4a as an oncogene, or cancer associated gene, is well established. It is implicated in prostate tumors, where it is overexpressed, and stimulates cell proliferation in colon cancer cells, where it promotes formation of the tumor itself. In lung cancer cell lines, where Kdm4a is also overexpressed, it coordinates with other oncogenes (like Ras) to transform normal cells into cancerous cells by inhibiting tumor suppressor pathways such as p53. Suppression of Kdm4a in breast cancer cell lines has shown to reduce cancer cell proliferation through cell cycle arrest, and decrease tumor migration and invasion.