title: Suppression of myeloid cell leukemia-1 (Mcl-1) enhances chemotherapy-associated apoptosis in gastric cancer cells.
abstract: BACKGROUND
  Myeloid cell leukemia-1 (Mcl-1) is an anti-apoptotic protein that regulates apoptosis sensitivity in a variety of cell types. Here we evaluate the roles of Mcl-1 in chemotherapy-associated apoptosis in gastric cancer cells. In addition, our study examined whether Mcl-1 contributed to apoptosis resistance in so-called cancer stem cell (CSC)-like populations in gastric cancer.
  
  
  METHODS
  Seven gastric cancer cell lines were used. The expression of Mcl-1 was assessed by either real-time polymerase chain reaction or Western blot analysis. Apoptosis was quantitated by morphological observation and caspase activity measurement. Adenovirus-mediated RNA interference (RNAi) technology was used to knockdown the expression of Mcl-1. The release of cytochrome c was evaluated by subcellular fractionation and immunoblot analysis. To identify and isolate the CSC-like populations, we used the CSC-associated cell surface marker CD44 and flow cytometry.
  
  
  RESULTS
  Six out of the 7 gastric cancer cell lines overexpressed Mcl-1 protein. These Mcl-1-expressing cell lines were relatively resistant to chemotherapeutic agents such as 5-fluorouracil (5-FU) and cisplatin (CDDP). Depletion of Mcl-1 protein by RNAi technology effectively sensitized the cells to anticancer drug-induced mitochondrial cytochrome c release, caspase activation, and apoptosis. In addition, vast amounts of Mcl-1 mRNA were expressed in CD44-positive CSC-like cells. Mcl-1 suppression enhanced the apoptosis in CD44-positive cells to a level equivalent to that in CD44-negative cells, suggesting that Mcl-1 mediates chemotherapy resistance in CSC-like populations.
  
  
  CONCLUSIONS
  These results suggest that Mcl-1 mediates the resistance to apoptosis in gastric cancer cells by blocking the mitochondrial pathway of cell death. Mcl-1 depletion appears to be an attractive strategy to overcome chemotherapy resistance in gastric cancer cells.
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Internal Medicine, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
authors.forename: Hideko
authors.initials: H
authors.lastname: Akagi
authors.forename: Hajime
authors.initials: H
authors.lastname: Higuchi
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Sumimoto
authors.forename: Toru
authors.initials: T
authors.lastname: Igarashi
authors.forename: Ayano
authors.initials: A
authors.lastname: Kabashima
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Mizuguchi
authors.forename: Motoko
authors.initials: M
authors.lastname: Izumiya
authors.forename: Gen
authors.initials: G
authors.lastname: Sakai
authors.forename: Masayuki
authors.initials: M
authors.lastname: Adachi
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Funakoshi
authors.forename: Shoko
authors.initials: S
authors.lastname: Nakamura
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Hamamoto
authors.forename: Takanori
authors.initials: T
authors.lastname: Kanai
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Takaishi
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Kawakami
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Hibi
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008928:Mitochondria / Q000378:metabolism; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D014411:Neoplastic Stem Cells / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D060888:Real-Time Polymerase Chain Reaction; D013274:Stomach Neoplasms / Q000188:drug therapy* / Q000473:pathology
chemical_list: D000970:Antineoplastic Agents; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D019253:Proto-Oncogene Proteins c-bcl-2