One possible reason for the apparent discrepancies is that the experiments for studying the relationship among JMJD2D, p53, and p21 by Janknecht et al. are only performed in the systems of p21 promoter reporter assay in HEK293T cells and ectopic overexpression of JMJD2D in U2OS cells, which may generate some artificial effects not to reflect the natural relationship among JMJD2D, p53, and p21 in cancer cells. The gene discussed is KDM4D; the disease is cancer.