CDK4 and nasopharyngeal carcinoma: HBP1 promoted the proliferation in NPC cells by increasing CCND1 and CCND3 expression via directly interacting with their promoters, and decreasing p21Waf1/Cip1 and p27Kip1, that the CDK2-CCNE1, CDK4-CCND1, CDK6-CCND3 complexes would be activated to promote G1 to S phase process.