Allogeneic partially HLA-matched dendritic cells (DC) as a vaccine in metastatic renal cell cancer (mRCC): Final analysis of a clinical phase I/II study.
ABSTRACT
Background: Despite novel kinase inhibitors, prognosis of metastatic RCC remains poor and new experimental approaches are warranted. Our aim was to evaluate a DC-based vaccine, which exploits alloreactivity as a means to amplify specific anti-tumor immune responses.
Methods: Allogeneic, partially HLA-matched DC were generated in our GMP facility. DC were loaded with autologous tumor lysate. 8 patients with progressive mRCC were included, 7 patients were immunized repetitively with 107 DC s.c. over 20 weeks. Low-dose IL-2 (3 Mio U s.c. qd) was used concomitantly. Endpoints of the study were feasibility, safety, immunological and clinical responses. T cell responses against HLA-A2-restricted RCC-associated antigens were evaluated by proliferation assays, ELISpot and cytokine bead array (CBA). T cell repertoire was analysed by T cell receptor γ and –β PCR.
Results: Vaccination was feasible and safe, no treatment-related grade 3/4 toxicity or clinically relevant autoimmunity was observed. No objective responses were observed, however, 2/7 patients showed stable disease, one a minimal clinical response. The mean TTP was 24.6 weeks (range 5 to 96). Delayed-type hypersensitivity was detected in 3/7 and HLA antibodies were induced in 3/7 patients. In 3/7 patients T cell responses against RCC-associated antigens such as TYMS, G250, vimentin, surviving and cyclin-D1 were induced by vaccination. These antigen-specific T cells showed a predominant TH1-cytokine profile. Interestingly, a clonally expanded T cell population could be detected by γ- and –β PCR in one patient with both a minimal clinical response and a T cell response. This clone is currently persisting for more than 80 months, its specificity is under investigation.
Conclusions: Vaccination with allogeneic tumor-lysate-loaded DC was feasible, safe and was able to induce TH1-polarized immune responses against RCC-associated antigens. Tumor vaccination might be a promising approach in minimal residual disease, possibly in combination with antibodies against CTLA-4 or PD-1.