These results indicate that compared with radiotherapy alone, overexpression of Notch2 in combination with radiotherapy induced more DNA damage, enhanced the apoptosis of NPC cells by upregulating Bax and promoted G2/M blockade by downregulating the cell cycle protein Cyclin D1, all of which contributed to the enhanced radiosensitivity of NPC cells. This evidence concerns the gene CCND1 and nasopharyngeal carcinoma.