More interestingly, a positive feedback loop of CDK4-c-Myc-miR-15a was observed, which was similar to our previous report for CTGF-C-Jun/C-Myc-miR-18b and CDK4-E2F1-let-7c which promotes NPC pathogenesis [6, 17]. Here, E2F1 is linked to nasopharyngeal carcinoma.