Most of radioresistant NPCs with low RKIP expression along with data from the in vitro and in vivo radioresponse study indicate that RKIP is needed for ionizing radiation to kill NPC cells, and induction of RKIP expression can be an effective adjuvant for radiotherapy of NPCs with RKIP reduction. This evidence concerns the gene PEBP1 and nasopharyngeal carcinoma.