Effect of Transforming Growth Factor-beta1 on Expressions of Epidermal Growth Factor and Transforming Growth Factor-alpha in DU145 Androgen-Independent Prostate Cancer Cells

Shin, Ki Yong; Kong, Gu; Choi, Ho Seong; Lee, Jong Jin; Lee, Tchun Yong

Abstract

PURPOSE: This study was designed to identify the possible mechanism of insensitivity of DU145 prostate cancer cells to the transforming growth factor (TGF)-beta1-mediated growth inhibition.
MATERIALS AND METHODS
DU145 cells were treated with 4, 40, 100 pM TGF-beta1 for 3, 6, 9 days. Initially we performed the growth assay. After that, we analysed the change of cell cycle using fluorescence flow cytometry. At each time point, Western blot analysis with cell pellets was performed to investigate the change of expressions of epidermal growth factor(EGF), TGF-alpha, EGF receptor(EGFR) and TGF receptorII(TbetaR-II) proteins.
RESULTS
The growth rate of TGF-beta1-treated cells was initially suppressed, but over time returned to control level. Flow cytometric analysis revealed that TGF-beta1-treated cells showed an increase in apoptotic/G1 phases, and concurrent decrease in S, G2/M phases until 6days. On day 9, however, TGF-beta1-treated cells showed a persistent increase of apoptotic unclei in spite of recovery of apoptotic/G1, S and G2/M phases. Western blot analysis showed that the intensity of EGF or TGF-alpha band decreased in dose-sependent manner on day 6. However, the intensity of each band increased up to the control level on day 9. the expression of EGFR or TbetaR-II protein did not change after treatment of TGF-beta1.
CONCLUSIONS
these results suggest that EGF and TGF-alpha sould mediate in part the escape fron the inhibitory effect of TGF-beta1 in DU145 cells.