Human clusterin gene expression is confined to surviving cells during in vitro programmed ce11 death. J Clin lnvest 93

Clusterin is a serum glycoprotein endowed with cell aggregat-ing, complement inhibitory, and lipid binding properties, and is also considered as a specific marker of dying cells, its expres-sion being increased in various tissues undergoing programmed cell death (PCD). However, no study has so far directly shown that cells expressing clusterin in these tissues are actually apoptotic as defined by morphological and biochemical criteria. We have studied cellular clusterin gene expression in vitro us-ing three different models of PCD: (a) ultraviolet B (UV-B) irradiation of human U937, HeLa, and A431 cell lines, (b) in vitro aging of human peripheral blood neutrophils (PMNs), and (c) dexamethasone-induced cell death of the human Iym-phoblastoid cell line CEM-C7. In all three models, the classical morphological and biochemical features of PCD observed did not correlate with an increase, but with either a marked de-crease or an absence of clusterin gene expression as assessed by Northern blot analysis. In situ hybridization of U937 and A431 cells after UV-B irradiation revealed, in addition, that only mor-phologically normal cells that are surviving continue to express the clusterin gene. Our results demonstrate that in the human myeloid, lym-phoid, and epithelial cell types studied, clusterin gene expres-sion is not a prerequisite to their death by apoptosis. In addi-tion, and most interestingly, in situ hybridization of U937 and A431 cells revealed that only surviving cells express the clus-terin gene after the induction of PCD, thus providing novel evidence suggesting that clusterin may be associated with cell survival within tissues regressing as a consequence of PCD. (J. Clin. Invest. 1994. 93:877-884.) Key words: apoptosis * com-plement * testosterone repressed prostate message-2 * apolipo-protein-J * lipi