MUC1 expressing tumor growth was retarded after human mucin 1 (MUC1) plasmid DNA immunization

INTRODUCTION: Naked DNA is one of the attractive tools for vaccination studies. We studied naked DNA vaccination against the human tumor antigen, mucin, which is encoded by the MUC1 gene. METHODS: We constructed the pcDNA3.0-MUC1 (pcDNA-MUC1) plasmid expressing an underglycosylated MUC1 protein. BALB/c mice were immunized intradermally thrice at 2-weeks intervals with pcDNA-MUC1. Two weeks after the last immunization, tumor challenge experiments were performed using either the CT26 or TA3HA tumor cell lines, both of which transduce human MUC1. RESULTS: Immune cell population monitoring from pcDNA-MUC1-immunized animals indicated that immune cell activation was induced by MUC1-specific immunization. Using intracellular fluorescence activated cell sorting and enzyme-linked immunosorbent spot assay, we reported that interferon-γ secreting CD8(+) T cells were mainly involved in MUC1-specific immunization. In all mice immunized with MUC1 DNA, tumor growth inhibition was observed, whereas control mice developed tumors (p < 0.001). CONCLUSION: Our results suggest that intradermal immunization with MUC1 DNA induces MUC1-specific CD8(+) T cell infiltration into tumors, elicits tumor-specific Th1-type immune response, and inhibits tumor growth.