Furthermore, overexpression of CDK4 has been showed in many tumor types, including oral squamous cell carcinoma[3], pancreatic endocrine tumors[4], lung cancer[5,6], and nasopharyngeal carcinoma[7], suggesting that CDK4 is a key factor in promoting the initiation and development of tumors. Here, CDK4 is linked to pancreatic neuroendocrine tumor.