Vaccination with ENO1 DNA Prolongs Survival of Genetically Engineered Mice with Pancreatic Cancer

BACKGROUND & AIMS:: Pancreatic ductal adenocarcinoma (PDA) is an aggressive tumor, and patients typically present with late-stage disease; rates of 5-year survival after pancreaticoduodenectomy are low. Antibodies against -enolase (ENO1), a glycolytic enzyme, are detected in more than 60% of patients with PDA, and ENO1-specific T cells inhibit the growth of human pancreatic xenograft tumors in mice. We investigated whether an ENO1DNA vaccine elicits anti-tumor immune responses and prolongs survival of mice that spontaneously develop autochthonous, lethal pancreatic carcinomas. METHODS:: We injected and electroporated a plasmid encoding ENO1 (or a control plasmid) into Kras(G12D)/Cre mice (KC) and Kras(G12D)/Trp53 (R172H) /Cre (KPC) mice when they were 4 weeks old (when pancreatic intraepithelial lesions are histologically evident). Anti-tumor humoral and cellular responses were analyzed by histology, immunohistochemistry, ELISAs, flow cytometry, and ELISpot and cytotoxicity assays. Survival was analyzed by Kaplan-Meier analysis. RESULTS:: The ENO1 vaccine induced antibody and a cellular responses and increased survival times by a median 138 days in KC mice and 42 days in KPC mice, compared with mice given the control vector. In histologic analysis, the vaccine appeared to slow tumor progression. The vaccinated mice had increased serum levels of anti-ENO1 immunoglobulin G, which bound the surface of carcinoma cells and induced complement-dependent cytotoxicity. ENO1 vaccination reduced numbers of myeloid-derived suppressor cells and T-regulatory cells, and increased T-helper 1 and 17 responses. CONCLUSIONS:: In a genetic model of pancreatic carcinoma, vaccination with ENO1DNA elicits humoral and cellular immune responses against tumors, delays tumor progression, and significantly extends survival. This vaccination strategy might be developed as a neo-adjuvant therapy for patients with PDA