Use of a recombinant Salmonella enterica serovar Typhimurium strain expressing C-Raf for protection against C-Raf induced lung adenoma in mice.
BACKGROUND
Serine-threonine kinases of the Raf family (A-Raf, B-Raf, C-Raf) are central players in cellular signal transduction, and thus often causally involved in the development of cancer when mutated or over-expressed. Therefore these proteins are potential targets for immunotherapy and a possible basis for vaccine development against tumors. In this study we analyzed the functionality of a new live C-Raf vaccine based on an attenuated Salmonella enterica serovar Typhimurium aroA strain in two Raf dependent lung tumor mouse models.


METHODS
The antigen C-Raf has been fused to the C-terminal secretion signal of Escherichia coli alpha-hemolysin and expressed in secreted form by an attenuated aroA Salmonella enterica serovar Typhimurium strain via the alpha-hemolysin secretion pathway. The effect of the immunization with this recombinant C-Raf strain on wild-type C57BL/6 or lung tumor bearing transgenic BxB mice was analyzed using western blot and FACS analysis as well as specific tumor growth assays.


RESULTS
C-Raf antigen was successfully expressed in secreted form by an attenuated Salmonella enterica serovar Typhimurium aroA strain using the E. coli hemolysin secretion system. Immunization of wild-type C57BL/6 or tumor bearing mice provoked specific C-Raf antibody and T-cell responses. Most importantly, the vaccine strain significantly reduced tumor growth in two transgenic mouse models of Raf oncogene-induced lung adenomas.


CONCLUSIONS
The combination of the C-Raf antigen, hemolysin secretion system and Salmonella enterica serovar Typhimurium could form the basis for a new generation of live bacterial vaccines for the treatment of Raf dependent human malignancies.
Gentschev
Ivaylo
I
Institut für Medizinische Strahlenkunde und Zellforschung (MSZ), University of Wuerzburg, D-97078 Wuerzburg, Germany. ivaylo.gentschev@mail.uni-wuerzburg.de
Fensterle
Joachim
J
Schmidt
Andreas
A
Potapenko
Tamara
T
Troppmair
Jakob
J
Goebel
Werner
W
Rapp
Ulf R
UR
D000236:Adenoma / Q000517:prevention & control*; D000818:Animals; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D019496:Cancer Vaccines / Q000276:immunology* / Q000627:therapeutic use; D029968:Escherichia coli Proteins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D006460:Hemolysin Proteins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D007111:Immunity, Cellular; D007114:Immunization / Q000379:methods; D008175:Lung Neoplasms / Q000517:prevention & control*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D010957:Plasmids / Q000235:genetics; D019908:Proto-Oncogene Proteins c-raf / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D011994:Recombinant Proteins / Q000276:immunology / Q000627:therapeutic use; D012486:Salmonella typhimurium / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D014613:Vaccines, Attenuated / Q000276:immunology / Q000627:therapeutic use
D019496:Cancer Vaccines; D029968:Escherichia coli Proteins; D006460:Hemolysin Proteins; C036507:Hlya protein, E coli; D011994:Recombinant Proteins; D014613:Vaccines, Attenuated; D019908:Proto-Oncogene Proteins c-raf