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Purpose: Local tumor ablation through irreversible electroporation (IRE) may offer a novel therapeutic option for locally advanced pancreatic cancer (LAPC). It may also serve as a means of in vivo vaccination. To obtain evidence of the induction of systemic antitumor immunity following local IRE-mediated ablation, we performed an explorative immune monitoring study. Methods: In ten patients enrolled in a clinical trial exploring the safety, feasibility, and efficacy of percutaneous image-guided IRE in LAPC, we determined the frequency and activation state of lymphocytic and myeloid subsets in pre- and post-treatment peripheral blood samples using flow cytometry. Tumor-specific systemic T cell responses to the pancreatic cancer associated antigen Wilms Tumor (WT)1 were determined after in vitro stimulation in an interferon-y enzyme-linked immunospot assay (Elispot), at baseline and at 2 weeks and 3 months after IRE. Results: Our data showed a transient decrease in systemic regulatory T cells (Treg) and a simultaneous transient increase in activated PD-1+ T cells, consistent with the temporary reduction of tumor-related immune suppression after the IRE procedure. Accordingly, we found post-IRE boosting of a pre-existing WT1 specific T cell response in two out of three patients as well as the de novo induction of these responses in another two patients. There was a trend for these WT1 T cell responses to be related to longer overall survival (p =.055). Conclusions: These findings are consistent with a systemic and tumor-specific immune stimulatory effect of IRE and support the combination of percutaneous IRE with therapeutic immune modulation. [ABSTRACT FROM AUTHOR]

Active immunotherapy may prevent the relapse of acute myeloid leukemia (AML) by inducing leukemia-specific T cells. Here, we investigated whether Wilms' tumor 1 (WT1) and preferentially expressed antigen in melanoma (PR AME)-specific T cells could be induced upon the priming of healthy donor- and AML patient-derived T cells with HLA-A2-matched, peptide-loaded allogeneic dendritic cells. AML-reactive, tetramer (Tm)-binding and interferon-producing, cytotoxic T lymphocytes specific for PR AME could readily be isolated from healthy individuals and maintained in culture. In this setting, priming efficacy was significantly higher for PR AME than for WT1. The priming of T cells from patient-derived material proved to be near-to-impossible: No leukemia-associated antigen (LAA)-specific T cell could be primed in 4 patients that had recently achieved a complete response (CR), and in only 1 out of 3 patients exhibiting a sustained CR we did observe WT1-specific T cells, though with a low frequency. These findings suggest that the functionality and/or repertoire of T cells differ in healthy subjects and AML patients in CR, and may have repercussions for the implementation of active vaccination approaches against AML. [ABSTRACT FROM AUTHOR]