title: Resistance of pancreatic cancer to gemcitabine treatment is dependent on mitochondria-mediated apoptosis.
abstract: Palliative chemotherapy with gemcitabine, a common mode of treatment of pancreatic cancer, has little influence on patients' survival. We investigated the impact of anti-apoptotic Bcl-xL protein and its antagonist Bax on gemcitabine-induced apoptosis in human pancreatic carcinoma cells in vitro and in vivo. The level of Bcl-xL and Bax expression was determined in 3 established pancreatic cancer cell lines that differ in their sensitivity to gemcitabine-mediated apoptosis. Bcl-xL and Bax genes were transduced into Colo357 cells by retroviral infection. In addition, cells were transfected with c-FLIP to assess involvement of CD95 and caspase-8. The impact of Bax/Bcl-xL expression on gemcitabine-sensitivity in vivo was evaluated in orthotopic Colo357 tumors in SCID mice. The apoptotic index revealed a strong inverse correlation between Bcl-xL expression and gemcitabine-induced apoptosis in the pancreatic carcinoma cell lines tested. Caspase-8 and Bid were cleaved in Colo357 cells exposed to gemcitabine, and there was no correlation with either Bcl-xL or with Bax expression. In contrast, the lack of mitochondrial transmembrane potential transition, release of cytochrome-c and absence of caspase-9- and PARP-cleavage showed a strong correlation with Bcl-xL expression. Expression of c-FLIP significantly increased the resistance towards gemcitabine. Orthotopically growing Colo357-bcl-xl tumors in SCID mice were refractory to gemcitabine treatment, and in contrast to the in vitro data, Colo357-bax tumors exhibited a 12-fold greater tumor regression than Colo357-wild-type tumors in the control group. Gemcitabine-induced apoptosis involves the mitochondria-mediated signaling pathway. A functional restoration of this pathway appears to be essential to overcome the resistance mechanisms of pancreatic tumor cells and to improve the response to therapy as demonstrated by Bax overexpression in a clinically relevant tumor model.
authors.affiliation: Clinic for General and Thoracic Surgery, Molecular Oncology Research Group, University of Kiel, Germany.
authors.forename: Bodo
authors.initials: B
authors.lastname: Schniewind
authors.forename: Matthias
authors.initials: M
authors.lastname: Christgen
authors.forename: Roland
authors.initials: R
authors.lastname: Kurdow
authors.forename: Sieglinde
authors.initials: S
authors.lastname: Haye
authors.forename: Bernd
authors.initials: B
authors.lastname: Kremer
authors.forename: Holger
authors.initials: H
authors.lastname: Kalthoff
authors.forename: Hendrik
authors.initials: H
authors.lastname: Ungefroren
mesh_terms: D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects*; D051023:BH3 Interacting Domain Death Agonist Protein; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins / Q000378:metabolism; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000627:therapeutic use*; D019008:Drug Resistance, Neoplasm; D005260:Female; D047908:Intracellular Signaling Peptides and Proteins; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008807:Mice, Inbred BALB C; D016513:Mice, SCID; D008928:Mitochondria / Q000187:drug effects*; D010190:Pancreatic Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D012190:Retroviridae / Q000235:genetics; D014407:Tumor Cells, Cultured; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D019014:fas Receptor / Q000378:metabolism; D000093542:Gemcitabine
chemical_list: D000964:Antimetabolites, Antineoplastic; D051023:BH3 Interacting Domain Death Agonist Protein; C494827:Bax protein, mouse; C494812:Bcl2l1 protein, mouse; C494815:Bid protein, mouse; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D002352:Carrier Proteins; C506387:Cflar protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D019014:fas Receptor; D003841:Deoxycytidine; D045304:Cytochromes c; D011065:Poly(ADP-ribose) Polymerases; C505530:CASP8 protein, human; C506433:CASP9 protein, human; C505526:Casp8 protein, mouse; C506434:Casp9 protein, mouse; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D000093542:Gemcitabine