Mitochondria-Targeting Drug Oligomycin Blocked P-Glycoprotein Activity and Triggered Apoptosis in Doxorubicin-Resistant HepG2 Cells.

Background: Mitochondria are key regulators in apoptosis. This suggests that a mitochondrion can be a target for cancer treatment. To examine the feasibility of this approach, we investigated the effect of oligomycin on the induction of apoptosis in drug-resistant cells. As a mitochondrion-targeting agent, oligomycin inhibits mitochondrial F₀F₁-ATPase. Of 37,000 molecules tested against the 60 human cancer cell lines of the National Cancer Institute, oligomycin is among the top 0.1% most cell line selective agents. Methods: Changes in the doxorubicin (Dox) accumulation and mitochondrial potential (Δψm) in human hepatocarcinoma HepG2 and its derivative R-HepG2 with Dox resistance were determined by flow cytometry. P-glycoprotein (Pgp) expression and release of cytochrome c from mitochondria were analyzed by Western blot. Cytotoxicity was examined by DNA fragmentation and the alamar blue assay. Results: R-HepG2 cells produced Pgp, showed drug resistance and accumulated less Dox when compared to their parent. In both cell lines, oligomycin depolarized Δψm, released cytochrome c and elicited DNA fragmentation. Moreover, oligomycin blocked Pgp activity and accumulated more Dox in R-HepG2. Combined treatment with Dox and oligomycin elicited more cell death. Conclusion: Our results suggest that oligomycin could bypass Dox resistance and trigger apoptosis in R-HepG2 cells.Copyright © 2004 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]