Enhanced anti-tumor effects of dendritic cells against glioblastoma by using cytoplasmic transduction peptide (CTP)-fused recombinant protein combined with anti-PD1

Background: Recent clinical trials utilizing antigen-pulsed dendritic cells have demonstrated increased survival of the vaccinated cancer patients. Besides, the cytoplasmic transduction peptide has not only excellent transcellular efficiency but also a strong tendency to remain in the cytoplasm after transduction without migrating into the nucleus. In this study, we investigated the effectiveness of immunotherapy against malignant gliomas using DCs pulsed with cytoplasmic transduction peptide (CTP)-fused recombinant protein combined with programmed cell death protein 1 blockade. Methods The expression of tumor associated antigen (WT1 and BIRC5) on glioblastoma target cells was confirmed by western blot. The effect of CTP-rhWT1 and/or CTP-rhBIRC5 on DCs was determined. The immunophenotypes of VaxDCs pulsed with CTP-rhWT1 and/or CTP-rhSBIRC5 was confirmed by flow cytometry and the cytokine production levels of T helper polarization were measured by enzyme-linked immunosorbent assay. The IFN-γ-enzyme linked immunospot assay and lactate dehydrogenase release assay were done to estimate the cytotoxic activity of CTLs stimulated by CTP-fused recombinant protein pulsed VaxDCs along with PD1 blockade against malignant glioma cells expressing WT1 and BIRC5. Results The CTP-rhWT1 and CTP-rhBIRC5 enhanced activating markers of DCs. Besides, the CTP-rhWT1 and CTP-rhBIRC5 combination resulted in Th1 cytokine polarization. The increase in number of IFN-γ-secreting cells paralleled with enhanced cytotoxicity of CTLs-stimulated by CTP-fused recombinant protein pulsed VaxDCs against glioblastoma target cells. Conclusions Our study suggested that treatment of CTP-fused recombinant protein along with PD1 blockade, which enhances cytotoxicity of DCs, could be an effective immunotherapy strategy for glioblastoma.