Preclinical Development Multiple Antigenic Peptides Based on H-2K–Restricted CTL Epitopes fromMurineHeparanase Induce aPotent Antitumor Immune Response In Vivo

Accumulating research suggests that heparanase may be a universal tumor-associated antigen (TAA). Several heparanase T-cell epitopes from humans and mice have already been identified. However, because of low immunogenicity, polypeptide vaccines usually have difficulty inducing effective antitumor immune responses in vivo. In this study, to increase the immunogenicity of polypeptide vaccines, we designed and synthesized two four-branch multiple antigenic peptides (MAP) on the basis of mouse heparanase (mHpa) Tcell epitopes (mHpa398 and mHpa519). The dendritic cells (DC) from mice bone marrow loaded with above MAP vaccines from heparanase were used to evaluate immune response against various tumor cell lines, compared with immune response to their corresponding linear peptides, ex vivo and in vivo. We further assessed IFN-g release both in CD4þ T-cell–depleted and nondepleted mice. The results showed that effectors generated from DCs, loaded with MAP-vaccinated mice splenocytes, induced a stronger immune response against target cells expressing both heparanase and H-2K than did effectors generated frommice vaccinated with their corresponding linear peptides. Heparanase-specific CD8þ T-cell responses induced by MAP and linear peptide vaccination required synergy of CD4þ T cells. In addition, heparanse-derived MAP vaccines significantly inhibited the growthofB16murinemelanoma inC57BL/6mice,while also increasing the survival rate of tumor-bearingmice. Our data suggest thatMAP vaccines based on T-cell epitopes from heparanase are efficient immunogens for tumor immunotherapy. Mol Cancer Ther; 11(5); 1183–92. 2012 AACR.