Cyclin D1 in human neuroendocrine: tumorigenesis.

Human neuroendocrine tumors exhibit unique biological properties, and defining the molecular genetic alterations that underlie these distinctive features remains an important challenge. In addition to the MEN1 tumor suppressor gene, the cyclin D1 oncogene has demonstrated a role in the pathogenesis of parathyroid and gastroenteropancreatic neuroendocrine tumors. Up-regulation of cyclin D1 is observed early in tumor formation, implying a possible role in tumor initiation. Overexpression of cyclin D1 in the parathyroid glands of mice resulted in the tandem regulation of cellular proliferation and hormonal secretion, a feature intrinsic to neuroendocrine tumors.