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01.12.2015 | Research article | Ausgabe 1/2015 Open Access

BMC Cancer 1/2015

Neoadjuvant administration of Semliki Forest virus expressing interleukin-12 combined with attenuated Salmonella eradicates breast cancer metastasis and achieves long-term survival in immunocompetent mice

BMC Cancer > Ausgabe 1/2015
M. Gabriela Kramer, Martín Masner, Erkuden Casales, María Moreno, Cristian Smerdou, José A. Chabalgoity
Wichtige Hinweise

Electronic supplementary material

The online version of this article (doi:10.​1186/​s12885-015-1618-x) contains supplementary material, which is available to authorized users.

Competing interests

The authors declare that they have no competing interests.

Authors’ contribution

MGK conceived and supervised the project, carried out all surgeries and in vivo experiments, analyzed the data, prepared the final illustrations and wrote the manuscript. MMa performed the ELISAs, clonogenic and immunohistochemical assays and helped with statistical and in vivo studies. EC produced and titrated the SFV-IL-12 and SFV-LacZ vectors used in this work. MMo provided orientation for MMa to perform the initial immunological analysis. CS and JACh supplied the viral vectors and attenuated bacteria, respectively, and critically revised the manuscript. All authors contributed with enriching discussions. All authors read and approved the final manuscript.



Metastatic breast cancer is a major cause of death among women worldwide; therefore efficient therapeutic strategies are extremely needed. In this work we have developed a gene therapy- and bacteria-based combined neoadjuvant approach and evaluated its antitumor effect in a clinically relevant animal model of metastatic breast cancer.


2×108 particles of a Semliki Forest virus vector expressing interleukin-12 (SFV-IL-12) and/or 2×107 units of an aroC Samonella Typhimurium strain (LVR01) were injected into 4T1 tumor nodules orthotopically implanted in mice. Tumors were surgically resected and long-term survival was determined. IL-12 and interferon-γ were quantified by Enzyme-Linked ImmunoSorbent Assay, bacteria was visualized by inmunohistochemistry and the number of lung metastasis was calculated with a clonogenic assay.


SFV-IL-12 and LVR01 timely inoculated and followed by surgical resection of tumors succeeded in complete inhibition of lethal lung metastasis and long-term survival in 90 % of treated mice. The combined therapy was markedly synergistic compared to each treatment alone, since SFV-IL-12 monotherapy showed a potent antiangiogenic effect, being able to inhibit tumor growth and extend survival, but could not prevent establishment of distant metastasis and death of tumor-excised animals. On the other hand, LVR01 alone also showed a significant, although limited, antitumor potential, despite its ability to invade breast cancer cells and induce granulocyte recruitment. The efficacy of the combined therapy depended on the order in which both factors were administered; inasmuch the therapeutic effect was only observed when SFV-IL-12 was administered previous to LVR01, whereas administration of LVR01 before SFV-IL-12 had negligible antitumor activity. Moreover, pre-treatment with LVR01 seemed to suppress SFV-IL-12 antiangiogenic effects associated to lower IL-12 expression in this group. Re-challenged mice were unable to reject a second 4T1 tumor; however 100 % of them could be totally cured by applying the same neoadjuvant combined regimen. To our knowledge, these are the most encouraging results obtained to date in a post-operatory setting using the highly aggressive 4T1 animal model.


SFV-IL-12-based gene therapy combined with Salmonella LVR01 neoadjuvant administration has a synergic antitumor effect and may be a promising therapeutic option to prevent and/or eradicate pre-operatory metastasis in locally advanced breast cancer.
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