title: A Legumain-based minigene vaccine targets the tumor stroma and suppresses breast cancer growth and angiogenesis.
abstract: Tumor associated macrophages (TAMs) are well known to play a very important role in tumor angiogenesis and metastasis. The suppression of TAMs in the tumor-microenvironment (TME) provides a novel strategy to inhibit tumor growth and dissemination by remodeling the tumor's stroma. Here, we tested our hypothesis that suppression of TAMs can be achieved in syngeneic BALB/c mice with oral minigene vaccines against murine MHC class I antigen epitopes of Legumain, an asparaginyl endopeptidase and a member of the C13 family of cystine proteases which is overexpressed on TAMs in the tumor stroma. Vaccine vectors were constructed and transformed into attenuated Salmonella typhimurium (Dam ( - ) , AroA ( - )) for oral delivery. Groups of mice received either the expression vectors encoding the Legumain H-2D or 2K epitopes or the control empty vector by gavage. The efficacy of the minigene vaccines was determined by their ability to protect mice from lethal tumor cell challenges, the induction of a specific CTL response as well as IFN-gamma release, and inhibition of tumor angiogenesis. We demonstrated that the Legumain minigene vaccine provided effective protection against tumor cell challenge by inducing a specific CD8+ T-cell response against Legumain+ TAMs in our breast tumor model. The protection, induced by this T-cell response, mediated by the Legumain Kd minigene, is also responsible for lysing D2F2 breast carcinoma cells in syngeneic BALB/c mice and for suppressing tumor angiogenesis. Importantly, in a prophylactic setting, the minigene vaccine proved to be of similar anti-tumor efficacy as a vaccine encoding the entire Legumain gene. Together, our findings establish proof of concept that a Legumain minigene vaccine provides a more flexible alternative to the whole gene vaccine, which may facilitate the future design and clinical applications of such a vaccine for cancer prevention.
authors.affiliation: Department of Immunology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
authors.forename: Susanna
authors.initials: S
authors.lastname: Lewēn
authors.forename: He
authors.initials: H
authors.lastname: Zhou
authors.forename: Huai-dong
authors.initials: HD
authors.lastname: Hu
authors.forename: Tingmei
authors.initials: T
authors.lastname: Cheng
authors.forename: Dorothy
authors.initials: D
authors.lastname: Markowitz
authors.forename: Ralph A
authors.initials: RA
authors.lastname: Reisfeld
authors.forename: Rong
authors.initials: R
authors.lastname: Xiang
authors.forename: Yunping
authors.initials: Y
authors.lastname: Luo
mesh_terms: D000818:Animals; D019496:Cancer Vaccines / Q000276:immunology*; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000276:immunology*; D003602:Cytotoxicity, Immunologic; D005260:Female; D015395:Histocompatibility Antigens Class I / Q000276:immunology; D008264:Macrophages / Q000276:immunology* / Q000378:metabolism; D008325:Mammary Neoplasms, Experimental / Q000098:blood supply / Q000276:immunology / Q000517:prevention & control*; D051379:Mice; D008807:Mice, Inbred BALB C; D009389:Neovascularization, Pathologic / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D019444:Vaccines, DNA / Q000276:immunology*; D000099240:Asparaginyl Endopeptidase