High hydrostatic pressure affects antigenic pool in tumor cells: Implication for dendritic cell-based cancer immunotherapy

- Human cancer cell lines differ in sensitivity to HHP-induced antigen degradation.
- DC loaded with 200 MPa-killed immunogenic lung tumor cells induce CD8+ T cells.
- 200 MPa HHP is optimal for immunogenic DC-based lung cancer vaccine generation.

High hydrostatic pressure (HHP) can be used to generate dendritic cell (DC)-based active immunotherapy for prostate, lung and ovarian cancer. We showed here that HHP treatment of selected human cancer cell lines leads to a degradation of tumor antigens which depends on the magnitude of HHP applied and on the cancer cell line origin. Whereas prostate or ovarian cell lines displayed little protein antigen degradation with HHP treatment up to 300 MPa after 2 h, tumor antigens are hardly detected in lung cancer cell line after treatment with HHP 250 MPa at the same time. On the other hand, quick reduction of tumor antigen-coding mRNA was observed at HHP 200 MPa immediately after treatment in all cell lines tested. To optimize the DC-based active cellular therapy protocol for HHP-sensitive cell lines the immunogenicity of HHP-treated lung cancer cells at 150, 200 and 250 MPa was compared. Lung cancer cells treated with HHP 150 MPa display characteristics of immunogenic cell death, however cells are not efficiently phagocytosed by DC. Despite induction of the highest number of antigen-specific CD8+ T cells, 150 MPa-treated lung cancer cells survive in high numbers. This excludes their use in DC vaccine manufacturing. HHP of 200 MPa treatment of lung cancer cells ensures the optimal ratio of efficient immunogenic killing and delivery of protein antigens in DC. These results represent an important pre-clinical data for generation of immunogenic killed lung cancer cells in ongoing NSCLC Phase I/II clinical trial using DC-based active cellular immunotherapy (DCVAC/LuCa).