[Molecular mechanisms of DHEA and DHEAs on apoptosis and cell cycle arrest via Akt pathway in hepatoma cell lines].

OBJECTIVE

To evaluate the anti-proliferation effects of dehydroepiandrosterone (DHEAéand DHEA sulfate (DHEAs) on tumor cells.

METHODS

Human hepatoblastoma cells (HepG2) and colon adenocarcinoma cells (HT-29) were treated with DHEA and DHEAs of various concentrations. The cells were incubated for 8, 24, 48, and 72 hours, and the proliferation, apoptosis, cell cycle and the expression of phosphorylated Akt (Thr308 and Ser473) were analyzed using MTT assay, flow cytometry, and Western blotting at different time points. The influences of an inhibitor (LY294002) and an activator (hepatic growth factor; HGF) of PI3K on the effectiveness of DHEA were determined in HepG2 cells.

RESULTS

By increasing the concentrations of DHEA (1, 10, 50, 100, 200 micromol/L), the percentages of HepG2 and HT-29 survival cells treated with DHEA at 24 h were 92.7%+/-0.9%, 84.7%+/-1.2%, 62.4%+/-0.8%, 49.5%+/-0.8%, 50.7%+/-0.3% and 92.5%+/-0.4%, 89.5%+/-0.7%, 80.5%+/-1.1%, 67.5%+/-1.5%, 70.6%+/-0.6%, respectively. Proliferations of HepG2 and HT-29 cells were significantly inhibited after 24 hours of being incubated with 100 micromol/L DHEA treatment; the inhibition effect was stronger on HepG2 cells than on HT-29 cells. The effect of DHEAs on both cell lines on cell proliferation was weaker than that of the DHEA. In the cell cycle assay, DHEA treatment induced cell arrest in G0/G1 phase in both cell lines. Apoptosis of HepG2 cells was significantly triggered (18.6%+/-2.2%) by 100 micromol/L DHEA treatment for 24 hours, but not by DHEAs. In addition, 100 and 200 micromol/L DHEA treatments for 24 hours markedly inhibited phosphorylations of Akt (Thr308 and Ser473) in HepG2 cells, and these effects were enhanced by exposing them to LY294002 and stopped by exposing them to HGF. The anti-proliferative effects of DHEA on tumor cell lines were much stronger than those of DHEAs, and they were even stronger in HepG2 cells than in HT-29 cells.

CONCLUSION

Our results suggest that the induction of apoptosis through the inhibition of Akt signaling pathway is one of the anti-proliferative mechanisms of DHEA in certain tumors, but DHEA also promotes cell-cycle arrest.