title: Gemcitabine-mediated tumour regression and p53-dependent gene expression: implications for colon and pancreatic cancer therapy.
abstract: Gemcitabine is a chemotherapeutic that is widely used for the treatment of a variety of haematological malignancies and has become the standard chemotherapy for the treatment of advanced pancreatic cancer. Combinational gemcitabine regimes (e.g.with doxorubicin) are being tested in clinical trials to treat a variety of cancers, including colon cancer. The limited success of these trials has prompted us to pursue a better understanding of gemcitabine's mechanism of cell killing, which could dramatically improve the therapeutic potential of this agent. For comparison, we included gamma irradiation that triggers robust cell cycle arrest and Cr(VI), which is a highly toxic chemical that induces a robust p53-dependent apoptotic response. Gemcitabine induced a potent p53-dependent apoptosis that correlated with the accumulation of pro-apoptotic proteins such as PUMA and Bax. This is accompanied by a drastic reduction in p2l and 14-3-3σ protein levels, thereby significantly sensitizing the cells to apoptosis. In vitro and in vivo studies demonstrated that gemcitabine required PUMA transcription to instigate an apoptotic programme. This was in contrast to Cr(VI)-induced apoptosis that required Bax and was independent of transcription. An examination of clinical colon and pancreatic cancer tissues shows higher p53, p21, 14-3-3σ and Bax expression compared with matched normal tissues, yet there is a near absence of PUMA protein. This may explain why gemcitabine shows only limited efficacy in the treatment of these cancers. Our results raise the possibility that targeting the Bax-dependent cell death pathway, rather than the PUMA pathway, could result in significantly improved patient outcome and prognosis for these cancers.
authors.affiliation: Centre for Molecular and Structural Biomedicine, University of Algarve, Algarve, Portugal.
authors.forename: R
authors.initials: R
authors.lastname: Hill
authors.forename: M
authors.initials: M
authors.lastname: Rabb
authors.forename: P A
authors.initials: PA
authors.lastname: Madureira
authors.forename: D
authors.initials: D
authors.lastname: Clements
authors.forename: S A
authors.initials: SA
authors.lastname: Gujar
authors.forename: D M
authors.initials: DM
authors.lastname: Waisman
authors.forename: C A
authors.initials: CA
authors.lastname: Giacomantonio
authors.forename: P W K
authors.initials: PW
authors.lastname: Lee
mesh_terms: D048948:14-3-3 Proteins / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D002857:Chromium / Q000494:pharmacology / Q000627:therapeutic use; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000235:genetics*; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics; D004249:DNA Damage; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D008297:Male; D051379:Mice; D016513:Mice, SCID; D008954:Models, Biological; D010190:Pancreatic Neoplasms / Q000188:drug therapy* / Q000235:genetics*; D014176:Protein Biosynthesis / Q000187:drug effects; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D012074:Remission Induction; D014158:Transcription, Genetic / Q000187:drug effects; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D051028:bcl-2-Associated X Protein / Q000378:metabolism; D000093542:Gemcitabine
chemical_list: D048948:14-3-3 Proteins; D051017:Apoptosis Regulatory Proteins; C438378:BBC3 protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D011518:Proto-Oncogene Proteins; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D002857:Chromium; D003841:Deoxycytidine; C074702:chromium hexavalent ion; D000093542:Gemcitabine