Cyclin' toward dementia: Cell cycle abnormalities and abortive oncogenesisin Alzheimer disease

Recent evidence has associated the aberrant, proximal re-expression of vari ous cell cycle control elements with neuronal vulnerability in Alzheimer di sease, a chronic neurodegeneration. Such ectopic localization of various cy clins, cyclin-dependent kinases, and cyclin inhibitors in neurons can be se en as an attempt to re-enter the cell cycle. Given that primary neurons are terminally differentiated. any attempted re-entry into the cell division c ycle in this postmitotic environment will be dysregulated. Since successful dysregulation of the cell cycle is also the hallmark of a neoplasm, early cell-cycle pathophysiology in Alzheimer disease may recruit oncogenic signa l transduction mechanisms and, hence, can be viewed as an abortive neoplast ic transformation. (C) 2000 Wiley-Liss, Inc.