Effect of Sulfated Glycoprotein-2 (Clusterin) on Apoptosis of PC3 Cell Induced by Docetaxel

Choi, Jong Bo; Kim, Young Soo; Won, Nam Hee; Cho, Jae Heung

Abstract

PURPOSE: Sulfated glycoprotein-2 (SGP-2) is a glycoprotein that is secreted by mature mammalian Sertoli and epididymal epithelial cells, and has been previously identified as an apoptosis inhibitor. This study was undertaken to determine, whether anti-SGP-2 antibodies in combination with a chemotherapeutic agent improves the therapeutic outcome.
MATERIALS AND METHODS
Western blot analysis was performed to detect the changes in SGP-2 secretion from PC-3 cells after treating them with docetaxel (Taxotere ). The PC-3 cells were cultured and treated with various concentrations of docetaxel with 40 microgram/ml of anti-SGP-2 antibodies. In addition, the cultured PC-3 cells were treated with TNF-alpha at 10ng/ml with the SGP-2 antibodies. The number of viable cells was assessed by a trypan blue dye extraction assay after 24 hours. Using flowcytometric analysis, the exact extent of and changes in apoptosis after treatment with the anti-SGP-2 antibodies were assessed.
RESULTS
The percentage of viable PC-3 cells treated with docetaxel decreased with increasing docetaxel concentration. The percentage of viable PC-3 cells treated with docetaxel and anti-SGP-2 antibodies was lower in proportion to the docetaxel concentration. However these two groups were not statistically different. The percentage of viable PC-3 cells incubated with 10ng/ml TNF-alpha and the anti-SGP-2 antibodies were significantly lower compared to that for TNF-alpha alone (p<0.05). In the FACScan analysis, the number of apoptotic cells was not higher in the PC3 cells treated with docetaxel and anti SGP-2 antibodies compared to those treated with docetaxel alone.
CONCLUSIONS
These results showed that SGP-2 prevents TNF-alpha induced apoptosis primarily. However no difference in apoptosis between the docetaxel treated PC-3 cells and the docetaxel with the anti-SGP-2 antibodies treated PC-3 cells was observed. Therefore, the treatment outcome may not be improved by the combined therapy, involving blocking SGP-2 with Taxane based chemotherapy with the same cytotoxic mechanism as docetaxel.