Antiapoptotic small interfering RNA as potent adjuvant of DNA vaccination in a mouse mammary tumor model.
In vivo electroporation of plasmid DNA (DNA-EP) is an efficient and safe method for vaccines. It results in increased DNA uptake, enhances protein expression, and augments immune responses to the target antigen in a variety of species. To further improve the efficacy of DNA-EP, we evaluated small interfering RNA (siRNA) sequences targeting apoptotic genes as an adjuvant to cancer vaccine. Bak1 or Casp8 siRNA was coadministered with plasmid DNA encoding the extracellular and transmembrane domains of rat HER2 ECD.TM to BALB-neuT mice, which spontaneously develop HER2/neu-positive mammary tumors. The combination regimen significantly reduced spontaneous tumor progression in BALB-neuT mice, in an advanced disease setting, when compared with DNA-EP alone. The antitumor effect was associated with a noteworthy antibody isotype switch from IgG1 to IgG2a, when siRNA was coadministered with DNA-EP. CD8+ T cell responses increased significantly, as did the number of responders to vaccination. Coimmunization of siRNA and DNA-EP at the same physical location was essential for the enhanced therapeutic effect. Silencing of the targeted genes was confirmed by in vitro Western blots. siRNA sequences targeting apoptotic genes Bax and Fas did not improve tumor protection in this mouse model when compared with DNA-EP alone. These data demonstrate that some siRNA sequences can act in concert with DNA-EP to control HER2/neu-positive mammary carcinoma. These observations emphasize the potential of siRNA as adjuvant for therapeutic DNA vaccines.
Dharmapuri
Sridhar
S
Istituto di Ricerche di Biologia Molecolare P. Angeletti, 00040 Pomezia, Italy.
Aurisicchio
Luigi
L
Biondo
Antonella
A
Welsh
Natalie
N
Ciliberto
Gennaro
G
La Monica
Nicola
N
D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D000818:Animals; D000917:Antibody Formation / Q000187:drug effects; D017209:Apoptosis / Q000187:drug effects*; D053181:Caspase 8 / Q000378:metabolism; D004195:Disease Models, Animal; D018274:Electroporation; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D020868:Gene Silencing / Q000187:drug effects; D006367:HeLa Cells; D006801:Humans; D007111:Immunity, Cellular / Q000187:drug effects; D008325:Mammary Neoplasms, Experimental / Q000276:immunology* / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D010957:Plasmids / Q000235:genetics; D034741:RNA, Small Interfering / Q000276:immunology*; D051381:Rats; D014611:Vaccination; D019444:Vaccines, DNA / Q000276:immunology* / Q000627:therapeutic use*; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000378:metabolism
D000276:Adjuvants, Immunologic; C494773:Bak1 protein, mouse; D034741:RNA, Small Interfering; D019444:Vaccines, DNA; D050998:bcl-2 Homologous Antagonist-Killer Protein; D053181:Caspase 8