NKRF and leukemia: In HL-60 promyelocytic leukemia cell line, IL-8 mRNA was rapidly induced at high levels by PKC activator phorbol 12-myristate 13-acetate and unidentified negatively-acting transcriptional regulator(s) was suggested to involve in the modulatory effect of CHX on IL-8 mRNA induction [66], and consistently in human PMN, the IL-8 mRNA superinduction effect by CHX was also proposed to be due to its ability to prevent the de novo protein synthesis of NRF, a protein shown to repress IL-8 mRNA synthesis [67].