Muc1, Remodeled To Express Alpha-Gal Epitopes Immune-Based Therapy, Can Elicit Both Significant Prolonged Survival And Effective Antibody Production Against Multiple Tumor-Associated Antigens

MUC1, a membrane bound mucin glycoprotein, is overexpressed and aberrantly glycosylated in more than 80% of human pancreatic carcinoma, has generated considerable interest as a potential target for immunotherapy. MUC1 immune-based therapies have not been successful, because immunity toward tumor-associated antigens (TAAs) in cancer patients is weak and the presentation of TAAs to the immune system is poor. Human natural antibody, Anti-Gal is an IgG known to be present in large amounts in normal subjects and patients with malignancies, comprising ∼1% of serum circulating IgG. Anti-Gal specifically interacts with α-gal epitopes (Galα1, 3Galβ1, 4GlcNAc-R), synthesized by α1, 3 galactosyltransferase (α1,3GT) on cell surface glycolipids and glycoproteins. MUC1 remodeled to express α-gal epitopes (α-gal MUC1), because MUC1 has five potential sites of N-glycans, can bind anti-Gal in situ at the vaccination site. Such interaction would enhance the recognition by APCs, resulting in more effective vaccination. We previously investigated the effectiveness of elicitation of both antibody production and T cell responses against MUC1 antigen by α-gal MUC1 vaccination. Present study addresses the usefulness of α-gal MUC1 vaccination for prolongation of survival and antibodies production, including anti-MUC1 and Abs toward other TAAs. A human pancreatic cancer cell line, PANC1, which expresses MUC1 was employed and transfected with α1,3GT gene (α-gal PANC1). High anti-Gal α1,3GT KO mice, which displayed anti-Gal titers similar to those found in humans were generated by immunization of pig tissue. These mice were vaccinated with either 1 × 10 6 irradiated parental PANC1 (control group) or α-gal PANC1 (α-gal group). To demonstrate in vivo tumor destruction by α-gal PANC1 vaccination, vaccinated mice were injected s.c. with 0.5 × 10 6 B16 melanoma cells, which were transfected with MUC1 gene. The mean survival of either control or α-gal group were found to be 21.1±10.5 days or 41.1±10.4 days, respectively, and the survival of α-gal group was significantly prolonged (control vs. α-gal group; p=0.003). To understand the induced antibody response for other TAAs, immunostained PANC1 proteins were investigated in Western blots with mice serum before/after vaccination. Although the serum from control group fail to display the significant bands, which was reflected by both anti-MUC1 Ab and anti-unknown TAAs Abs, the serum from α-gal group contained multiple antibodies that bound to not only MUC1 but also different unknown TAAs. We conclude that vaccination with tumor lysate remodeled to express α-gal epitopes can effectively upregulated immunogenicity of multiple TAAs, including MUC1 but also other unknown TAAs and may provide a chance to develop the potential immunotherapy for pancreatic cancer patients. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4747.