Recently, HDACi entinostat has been shown to restore the decreased orphan nuclear receptor Nur77 expression in AML cell lines and in AML patient leukemia cells, especially in the leukemic stem/very early CD34+/38− progenitors, and induce apoptosis, presenting a novel mechanism of action of HDACi and suggesting that Nur77 may be a biomarker for HDACi apoptotic effect [51]. The gene discussed is NR4A1; the disease is acute myeloid leukemia.