Cancer Therapy: Preclinical A Therapeutic Her2/neu Vaccine Targeting Dendritic Cells Preferentially Inhibits the Growth of Low Her2/neu–Expressing Tumor in HLA-A2 Transgenic Mice Thi Tran 1,2 , Mariana O. Diniz 1,2,3 , Estelle Dransart 4,5,6 , Alain Gey 7 , Nathalie Merillon 1 , Yu Chun Lone 8 , Sylvie Godefroy 9 , Craig Sibley 9 , Luis CS Ferreira 3 , Jacques Medioni 10 , Stephane Oudard 1,2,10 , Ludger Johannes 4,5,6 , and Eric Tartour 1,2,7 Abstract Purpose: E75, a peptide derived from the Her2/neu protein, is the most clinically advanced vaccine approach against breast cancer. In this study, we aimed to optimize the E75 vaccine using a delivery vector targeting dendritic cells, the B-subunit of Shiga toxin (STxB), and to assess the role of various parameters (Her2/neu expression, combination with trastuzumab) in the efficacy of this cancer vaccine in a relevant preclinical model. Experimental Design: We compared the differential ability of the free E75 peptide or the STxB-E75 vaccine to elicit CD8 þ T cells, and the impact of the vaccine on murine HLA-A2 tumors expres- sing low or high levels of Her2/neu. Results: STxB-E75 synergized with granulocyte macrophage colony-stimulating factors and CpG and proved to be more efficient than the free E75 peptide in the induction of multifunc- tional and high-avidity E75-specific anti-CD8 þ T cells resulting in a potent tumor protection in HLA-A2 transgenic mice. High expression of HER2/neu inhibited the expression of HLA-class I molecules, leading to a poor recognition of human or murine tumors by E75-specific cytotoxic CD8 þ T cells. In line with these results, STxB-E75 preferentially inhibited the growth of HLA-A2 tumors expressing low levels of Her2/neu. Coadministration of anti-Her2/neu mAb potentiated this effect. Conclusions: STxB-E75 vaccine is a potent candidate to be tested in patients with low Her2/neu–expressing tumors. It could also be indicated in patients expressing high levels of Her2/neu and low intratumoral T-cell infiltration to boost the recruitment of T cells—a key parameter in the efficacy of anti-Her2/neu mAb therapy. Clin Cancer Res; 22(16); 4133–44. Ó2016 AACR. Introduction The Her2/neu proto-oncogene, is a validated target in cancer, as various anti-Her2/neu antibodies (trastuzumab, pertuzumab, adotrastuzumab emtansine, etc.) or tyrosine kinase inhibitors (lapatinib) demonstrated their clinical efficacy in patients with Her2/neu–overexpressing breast and gastric cancers. Unfortunate- ly, even after the best combination of Her2/neu–directed treat- ments and chemotherapy, the progression-free survival in patients with metastatic breast cancer is 18.7 months (1). Intrinsic properties of Her2/neu may explain the clinical efficacy of these approved drugs and the interest to develop other therapeutic approaches against this molecule. Indeed, its overexpression is required to maintain the malignant phenotype of these cancers and tumor escape by downregulation of Her2/ neu is thus more difficult to achieve. Cancer stem cells, which contribute to tumor metastasis and treatment resistance, express increased Her2/neu levels (2). Other arguments support the development of active immunotherapy such as anti-Her2/ neu T-cell vaccines to complement and improve the clinical activity of commercially available anti-Her2/neu antibodies. Her2/neu is immunogenic and elicits natural Her2/neu–specific T-cell responses in patients overexpressing this antigen (3, 4). Intratumoral T-cell infiltration is associated with a good prog- nosis in these patients (5) and the presence of high levels of tumor-infiltrating lymphocytes (TIL) were associated with increased trastuzumab benefit in Her2/neu þ breast cancer patients (6). The role of T cells in controlling Her2/neu–expressing tumors was also emphasized by the demonstration that intra- tumoral injection of human effector T cells genetically mod- ified to express chimeric antigen receptor (CAR) against Her2/ neu completely blocked the growth and metastasis of Her2/ neu–expressing pancreatic adenocarcinoma xenografts in SCID mice (7). 1 INSERM U970, Universit e Paris Descartes, Sorbonne Paris-Cit e, Paris, France. 2 Equipe Labellis ee Ligue Contre le Cancer, Paris, France. 3 Institute of Biomedical Sciences, University of S~ ao Paulo, S~ ao Paulo, Brazil. 4 Institut Curie, PSL Research University, Chemical Biology of Membranes and Therapeutic Delivery Unit. 5 INSERM, U 1143. 6 CNRS, UMR 3666, 26 rue d’Ulm, 75248 Paris Cedex 05, France. 7 Service d'Immunologie biologique, Hopital Europ een Georges Pompidou- APHP, Paris, France. 8 Inserm U-1014, Universit e Paris XI, Groupe Hos- pitalier Paul-Brousse, France. 9 Immuno Target SAS, Paris, France. 10 Service d'Oncologie M edicale, Hopital Europ een Georges Pompi- dou, Paris, France. Note: Supplementary data for this article are available at Clinical Cancer Research Online (http://clincancerres.aacrjournals.org/). L. Johannes and E. Tartour are the principal investigators of this article. Corresponding Author: Eric Tartour, Service d'Immunologie Biologique, H^ opital Europ een Georges Pompidou, 20 Rue Leblanc, Paris 75015, France. Phone: 331- 5609-3942; Fax: 331-5609-2080; E-mail: eric.tartour@aphp.fr doi: 10.1158/1078-0432.CCR-16-0044 Ó2016 American Association for Cancer Research. Clinical Cancer Research www.aacrjournals.org 4133 on May 5, 2020. © 2016 American Association for Cancer Research. clincancerres.aacrjournals.org Downloaded from Published OnlineFirst March 22, 2016; DOI: 10.1158/1078-0432.CCR-16-0044