Microsphere-based glypican-3 specific immunotherapy of hepatocellular carcinoma

• Applicant: Privatdozent Dr. Thomas Wirth
• Subject Area: Gastroenterology
• Term: from 2015 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 271680932

Immunotherapy represents a promising alternative to established cancer therapies thas has recently attracted a lot of attention due to promising clinical results in the therapy of solid cancers. Hepatocellular carcinoma represents an ideal target for immuntherapy due to its immunogenic features. While the use of co-inhibitory antibodies has already demonstrated clinical efficacy in individual patients, the attempts to generate cancer-specific vaccines only resulted in minor clinical effects due to low systemic immune responses.In experiments performed within the framwork of the SFB TRR77 "Liver cancer" we therfore tested various vaccination regimens to increase the magnitude of the tumor-specific immune response. We could show that the tumor-specific immune response could be both amplified and accelerated using a prime-boost vaccination regimen consisting of an immunization with antigen-coated PLGA microspheres, a TLR3 agonist and a subsequent booster vaccination with a Listeria monocytogenes vector.In addition to the vaccination studies, an autochthonous liver cancer model suitable for the evaluation of the vaccinations war developed. For this purpose, transposon-flanked plasmids were used that allow for the stable integration of any transgene into the cell's DNA. Using constitutively active NRAS, AKT, shRNA against p53 and the vaccination antigen, orthotopic liver cancers could be established wihin one week. In this tumor model, the combined PLGA/TLR3-Listeria vaccine induced comlete tumor regressions and was superior to conventional dendritic cell vaccination with regard to overall survival.In the proposed research project the spectrum of the vaccination antigens which has so far been restricted to the model antigen ovalbumin and the melanoma antigen TRP2 will be extended to the HCC-specific antigen Glypican-3. To this extent two Listeria vectors containing either human or murine Glypican-3 will be cloned. The murine Listeria vector LM-mGPC3 will then be tested in the context of the PLGA-LM prime boost vaccine for the therapy of Glypican-3 positive hepatocellular carcinoma in C57Bl/6 mice, in preparations for corresponding studies in humans. Additionally, cancer-specific, exhausted CD8 T cells will be isolated from tumor-bearing mice two weeks after the vaccination and subjected to whole genome microarray analysis to yield a transcriptional signature of T cell exhaustion. In subsequent experiments the functional relevance of the candidate genes identified in the T cells will be assessed to identify potential synergies with the PLGA/LM vaccination and to enable the generation of both potent and long-lasting cancer-specific immune responses.

• DFG Programme: Research Grants