INDUCTION OF NECROSIS BY ZINC IN PROSTATE CARCINOMA CELLS AND IDENTIFICATION OF PROTEINS INCREASED IN ASSOCIATION WITH THIS INDUCTION

Zinc exhibits inhibitory effects on apoptosis, and a deficiency in this metal generally causes this type of cell death to occur. In the present study, we found that exposure to zinc results in necrosis of prostate carcinoma cells. When zinc acetate was added to LNCaP or PC-3 cells in monolayer culture, they began to detach from the culture dishes, and viability was lost after 4−8 h. Most of the cell death was found to be due to necrosis as determined by double staining with fluorescein-isothiocyanate-labeled annexin V and ethidium bromide, and by detection of hypodiploid cells. Associated with the induction of necrosis was an increase in low molecular-mass proteins, identified by HPLC analysis to be thymosin β10, parathymosin and GAGE in LNCaP cells, and thymosin β4, parathymosin and metallothionein in PC-3. The time course of the increase of thymosin β10 in LNCaP cells and thymosin β4 in PC-3 cells was consistent with that of appearance of cell detachment and dead cells. These results indicate that zinc can induce necrosis and suggest that production of proteins including β-thymosins is involved in induction of processes leading to cell detachment.