Proapoptotic and antiapoptotic proteins of the Bcl-2 family regulate sensitivity of pancreatic cancer cells toward gemcitabine and T-cell-mediated cytotoxicity.
Sensitivity of carcinoma cells towards gemcitabine (Gem) has been linked to mitochondrial apoptotic proteins. Recently, we described synergistic efficacy of Gem-based chemoimmunotherapy and a dendritic cell (DC) tumor vaccine in a murine pancreatic carcinoma model. Here, we investigated the role of the mitochondrial proteins Bcl-2, Bcl-xL, and Bax for sensitization of pancreatic carcinoma cells toward T-cell-mediated cytotoxicity alone and in combination with Gem. Bcl-2 expression was silenced by siRNA in Panc02 pancreatic cancer cells expressing the model antigen ovalbumin (PancOVA). Tumor cells were treated with Gem and/or siRNA, and cytotoxicity induced by OVA-specific cytotoxic T lymphocytes (CTL) from OT-1 mice was assessed. Gem-induced and T-cell-induced cytotoxicity was also studied in human Colo357 pancreatic cancer cell lines overexpressing Bax or Bcl-xL. Apoptosis induction by Fas-activating antibody was measured by Annexin V staining. The in vivo capacity of Bcl-2 siRNA to augment CTL efficacy induced by DC vaccinations was assessed in C57BL/6 mice bearing PancOVA tumors. PancOVA cells treated with Bcl-2 siRNA were sensitized towards both Gem and T-cell-mediated killing; combination therapy exhibited an additive effect. Bax overexpression sensitized Colo357 cells to both Gem-mediated and T-cell-mediated cytotoxicity, whereas Bcl-xL overexpression was inhibitory. Combining Bcl-2 silencing with DC therapy improved tumor control in the PancOVA model in vivo without affecting the number of tumor-reactive CTL. In conclusion, expression of Bcl-2, Bcl-xL, and Bax in pancreatic tumor cells determines sensitivity towards both Gem-mediated and CTL-mediated toxicity. Bcl-2 silencing could be exploited therapeutically in tumor vaccine approaches.
*Section of Gastroenterology, Medizinische Klinik und Poliklinik IV, University of Munich ¶Division of Clinical Pharmacology, Center of Integrated Protein Science Munich (CIPS-M), Medizinische Klinik und Poliklinik IV, University of Munich ‡Institute of Molecular Immunology (IMI), Helmholtz Zentrum München §Immunotherapy Research Center, Immunis e.V., Munich †Institute of Pathology at Medizin Campus Bodensee, Friedrichshafen ∥Division of Molecular Oncology, Institute for Experimental Cancer Research, University of Kiel, Kiel #Kliniken St. Elisabeth, Department of Medicine II, Neuburg an der Donau, Germany.
Christian
C
Bauer
Claudia
C
Hees
Alexander
A
Sterzik
Franz
F
Bauernfeind
Rachel
R
Mak'Anyengo
Peter
P
Duewell
Hans-Anton
HA
Lehr
Elfriede
E
Noessner
Rudolf
R
Wank
Anna
A
Trauzold
Stefan
S
Endres
Marc
M
Dauer
Max
M
Schnurr
D000818:Animals; D000951:Antigens, Neoplasm / Q000276:immunology; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D019496:Cancer Vaccines; D045744:Cell Line, Tumor; D003602:Cytotoxicity, Immunologic / Q000235:genetics*; D003713:Dendritic Cells / Q000276:immunology / Q000378:metabolism; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004195:Disease Models, Animal; D018450:Disease Progression; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D005260:Female; D015870:Gene Expression; D020868:Gene Silencing; D006801:Humans; D007167:Immunotherapy; D051379:Mice; D010190:Pancreatic Neoplasms / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism / Q000473:pathology / Q000628:therapy; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics* / Q000378:metabolism; D034622:RNA Interference; D016176:T-Lymphocyte Subsets / Q000276:immunology* / Q000378:metabolism*; D047368:Tumor Burden / Q000187:drug effects / Q000235:genetics / Q000276:immunology; D023041:Xenograft Model Antitumor Assays; D051028:bcl-2-Associated X Protein / Q000235:genetics / Q000378:metabolism; D019014:fas Receptor / Q000235:genetics / Q000378:metabolism; D000093542:Gemcitabine
D000951:Antigens, Neoplasm; D000964:Antimetabolites, Antineoplastic; D019496:Cancer Vaccines; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D019014:fas Receptor; D003841:Deoxycytidine; D000093542:Gemcitabine