title: Mitochondria-targeting drug oligomycin blocked P-glycoprotein activity and triggered apoptosis in doxorubicin-resistant HepG2 cells.
abstract: 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 (Deltapsim) 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 Deltapsim, 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.
  
  
  CONCLUSIONS
  Our results suggest that oligomycin could bypass Dox resistance and trigger apoptosis in R-HepG2 cells.
authors.affiliation: Department of Biochemistry, The Chinese University of Hong Kong, Shatin, China.
authors.forename: Y C
authors.initials: YC
authors.lastname: Li
authors.forename: K P
authors.initials: KP
authors.lastname: Fung
authors.forename: T T
authors.initials: TT
authors.lastname: Kwok
authors.forename: C Y
authors.initials: CY
authors.lastname: Lee
authors.forename: Y K
authors.initials: YK
authors.lastname: Suen
authors.forename: S K
authors.initials: SK
authors.lastname: Kong
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D000970:Antineoplastic Agents / Q000378:metabolism / Q000494:pharmacology*; D017209:Apoptosis; D045744:Cell Line, Tumor; D045304:Cytochromes c / Q000378:metabolism; D053938:DNA Fragmentation / Q000187:drug effects; D004317:Doxorubicin / Q000378:metabolism / Q000494:pharmacology*; D016503:Drug Delivery Systems; D004347:Drug Interactions; D019008:Drug Resistance, Neoplasm; D006801:Humans; D008930:Mitochondria, Liver / Q000187:drug effects* / Q000378:metabolism; D009840:Oligomycins / Q000494:pharmacology*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D009840:Oligomycins; D004317:Doxorubicin; D045304:Cytochromes c