Protein changes associated with ionizing radiation-induced apoptosis in human prostate epithelial tumor cells

Ionizing radiation (IR) is an important component in the therapy of localiz ed prostate cancer. Identification of protein alterations during IR-induced apoptosis prostate cancer cells is an important step toward understanding the new metabolic status of the dying cell. In the present study, we report changes in protein profile that define the execution phase of the apoptoti c response in the in vitro model of tumorigenic radiation-transformed SV40- immortalized human prostate epithelial cells (267B1-XR), induced to undergo programmed cell death by IR. We employed an approach that involves use of analytical two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) co upled with Western blotting with specific antisera. Our results point out t hat apoptotic cells experience significant reduction in the levels of the i ntermediate filament proteins, keratins-18, 19, vimentin and the associated 14-3-3 adapter proteins. At the same time, molecular chaperones such as gl ucose-regulated protein 94, calreticulin, calnexin, and protein disulfide i somerase exhibit marked accumulation in these dying cells. The present data indicate that apoptosis-associated processes in prostate epithelial cells include solubilization of the rigid intermediate filament network by specif ic proteolysis as well as increased levels of endoplasmic reticulum (ER) pr oteins with chaperone functions.