Effect of Sulfated Glycoprotein-2 (Clusterin) on the Apoptosis of Prostatic Cancer

Yoon, Cheol Yong; Won, Nam Hee; Cho, Jae Heung

Abstract

PURPOSE: This study was performed to evaluate anti-apoptotic mechanism of Sulfated Glycoprotein-2 (SGP-2) in tumor necrosis factor-alpha (TNF-alpha) induced apoptosis of prostatic cancer cell.
MATERIALS AND METHODS
To suppress the activity of natively secreted SGP-2 by prostatic cancer cells, varying amount of the blocking antibody to SGP-2 (anti-SGP-2 antibody, 1.25~2.0microgram/ml) was applied. Then TNF-alpha or agonistic antibody to type I TNF-alpha receptor (agonistic-TNFR1 antibody) were applied for the induction of apop tosis. The changes of cell number and cytotoxicity were assessed by trypan blue dye exclusion assay. The exact amount of early and late apoptosis were analyzed and compared by flowcytometric analysis.
RESULTS
By blocking SGP-2 with anti-SGP-2 antibody (2.0microgram/ml), apoptosis was signi ficantly increased in both TNF-alpha (96.8 +/- 1.4%) and agonistic-TNFR1 antibody treated PC3 cells (95.2 +/- 0.9%) compared to control group (41.4 +/- 4.7%), especially after 36 hours incubation (p<0.05). The more suppressed the activity of SGP-2 by anti-SGP-2 antibody, significantly the more apoptosis was happened (p<0.05). After 24 hours incubation, the increase of apoptosis by the suppression of SGP-2 was significantly greater in TNF-alpha treated PC3 cells (45.6 +/- 27.6%) than in agonistic- TNFR1 antibody treated ones (28.6 +/- 4.7%). However after 36 hours the difference in degree of apop tosis between two groups disappeared.
CONCLUSIONS
We found that SGP-2 blocked the apoptosis which was induced by agonistic-TNFR1 antibody as like TNF-alpha induced one. These results implies the possi bility of the direct action of SGP-2 on type I TNF-alpha receptor. However the difference between two groups in the degree of apoptosis after 24 hours incubation period sug gest the more efficient blocking effect of SGP-2 on agonistic-TNFR1 induced apoptosis than on TNF-alpha induced one. For clarification of these difference, further research about other influencing factors such as type II TNF-alpha receptor activation is essential.