title: Down-regulation of mitochondrial F1F0-ATP synthase in human colon cancer cells with induced 5-fluorouracil resistance.
abstract: 5-Fluorouracil (5-FU) is widely used for treatment of advanced colorectal cancer. However, it is common for such patients to develop resistance to 5-FU, and this drug resistance becomes a critical problem for chemotherapy. The mechanisms underlying this resistance are largely unknown. To screen for proteins possibly responsible for 5-FU resistance, cells resistant to 5-FU were derived from human colon cancer cell lines and two-dimensional gel electrophoresis-based comparative proteomics was done. Two-dimensional gel electrophoresis data showed there was lower expression of the alpha subunit of mitochondrial F(1)F(0)-ATP synthase (ATP synthase) in 5-FU-resistant cells compared with parent cells. Western blotting showed that expression of other ATP synthase complex subunits was also lower in 5-FU-resistant cell lines and that these resistant cells also showed decreased ATP synthase activity and reduced intracellular ATP content. The ATP synthase inhibitor, oligomycin A, strongly antagonized 5-FU-induced suppression of cell proliferation. When 5-FU sensitivity was compared with ATP synthase activity in six different human colon cancer cell lines, a positive correlation has been found. Furthermore, suppressed ATP synthase d-subunit expression by siRNA transfection increased cell viability in the presence of 5-FU. Bioenergetic dysfunction of mitochondria has been reported as a hallmark of many types of cancers (i.e., down-regulation of ATP synthase beta-subunit expression in liver, kidney, colon, squamous oesophageal, and lung carcinomas, as well as in breast and gastric adenocarcinomas). Our findings show that ATP synthase down-regulation may not only be a bioenergetic signature of colorectal carcinomas but may also lead to cellular events responsible for 5-FU resistance.
authors.affiliation: Research Institute and Hospital, National Cancer Center, Goyang, Gyeonggi, 411-764, Korea.
authors.forename: Young-Kyoung
authors.initials: YK
authors.lastname: Shin
authors.forename: Byong Chul
authors.initials: BC
authors.lastname: Yoo
authors.forename: Hee Jin
authors.initials: HJ
authors.lastname: Chang
authors.forename: Eunkyung
authors.initials: E
authors.lastname: Jeon
authors.forename: Sung-Hye
authors.initials: SH
authors.lastname: Hong
authors.forename: Mi-Sun
authors.initials: MS
authors.lastname: Jung
authors.forename: Soo-Jeong
authors.initials: SJ
authors.lastname: Lim
authors.forename: Jae-Gahb
authors.initials: JG
authors.lastname: Park
mesh_terms: D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D001313:Aurovertins / Q000494:pharmacology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000201:enzymology* / Q000235:genetics; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm; D004734:Energy Metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005472:Fluorouracil / Q000494:pharmacology*; D006801:Humans; D008928:Mitochondria / Q000201:enzymology*; D025261:Mitochondrial Proton-Translocating ATPases / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics; D009840:Oligomycins / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics; D014162:Transfection
chemical_list: D000964:Antimetabolites, Antineoplastic; D001313:Aurovertins; D004791:Enzyme Inhibitors; D009840:Oligomycins; D034741:RNA, Small Interfering; C031004:oligomycin A; C034402:aurovertin B; C474451:F1F0-ATP synthase; D025261:Mitochondrial Proton-Translocating ATPases; D005472:Fluorouracil