Optimized construction of MUC1-VNTRn DNA vaccine and its anti-pancreatic cancer efficacy

Considering mucin 1-variable number tandem repeat (MUC1-VNTRn) as a novel target for pancreatic cancer immunotherapy, the present study aimed to screen and identify the pVAX1-MUC1-VNTRn DNA vaccine with the strongest immunogenicity. Following construction of a pVAX1-MUC1-VNTRn plasmid, immature dendritic cells (DCs) were subjected to transfection, and mature DCs were then co-cultured with autologous T-cells. The numbers of cytotoxic T lymphocytes (CTLs) secreting interferon (IFN)-γ were determined using an enzyme-linked immunospot assay, and CytoTox® was also used to examine the MUC1-VNTRn-specific Lethal effect of CTLs on Capan2 cells. Additional in vivo experiments in mice were performed to confirm the antitumor effect of the DNA vaccine candidate. The present study successfully constructed the pVAX1-MUC1-VNTRn plasmid, which expresses the target protein in eukaryotic cells. Additionally, upon uptake of the pVAX1-MUC1-VNTRn plasmid, the immature DCs differentiated into mature DCs. The levels of the DC surface molecules cluster of differentiation (CD) 80, CD86, human leukocyte antigen-antigen D related, interleukin (IL)-12, IL-17 and IFN-γ were significantly higher, while the levels of IL-10 and IL-14 were lower, in mature DCs of the stimulated groups compared with the immature DCs of the non-stimulated groups (all P<0.01). In addition, the MUC1-VNTR6 and MUC1-VNTR9 groups, in which DCs were capable of activating autologous T-cells, showed increased IFN-γ-producing T-cells compared with the other groups (strong MUC1-VNTR1, weak VNTR1, VNTR3, VNTR4 and MUC1-cDNA groups; all P<0.001). In addition, the Lethal effect of CTLs on Capan2 cells in these two groups was stronger compared with the other groups (all P<0.001). Furthermore, the induced protective and therapeutic immune responses in mouse experiments showed that the pVAX1-MUC1-VNTR6DNA vaccine likely possessed the strongest immunogenicity, and its ability to inhibit panc02-MUC1 tumor growth was superior to other DNA vaccines (P<0.01). The present study provides compelling evidence that pVAX1-MUC1-VNTRn has the potential to express the target protein in eukaryotic cells, and thatpVAX1-MUC1-VNTR6 was characterized by the strongest Lethal effect in both in vivo and in vitro experiments.