AUTHOR=Löffler Markus W. , Nussbaum Bianca , Jäger Günter , Jurmeister Philipp S. , Budczies Jan , Pereira Philippe L. , Clasen Stephan , Kowalewski Daniel J. , Mühlenbruch Lena , Königsrainer Ingmar , Beckert Stefan , Ladurner Ruth , Wagner Silvia , Bullinger Florian , Gross Thorben H. , Schroeder Christopher , Sipos Bence , Königsrainer Alfred , Stevanović Stefan , Denkert Carsten , Rammensee Hans-Georg , Gouttefangeas Cécile , Haen Sebastian P. 

TITLE=A Non-interventional Clinical Trial Assessing Immune Responses After Radiofrequency Ablation of Liver Metastases From Colorectal Cancer

JOURNAL=Frontiers in Immunology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2019.02526

DOI=10.3389/fimmu.2019.02526

ISSN=1664-3224

ABSTRACT=<p><bold>Background:</bold> Radiofrequency ablation (RFA) is an established treatment option for malignancies located in the liver. RFA-induced irreversible coagulation necrosis leads to the release of danger signals and cellular content. Hence, RFA may constitute an endogenous <italic>in situ</italic> tumor vaccination, stimulating innate and adaptive immune responses, including tumor-antigen specific T cells. This may explain a phenomenon termed abscopal effect, namely tumor regression in untreated lesions evidenced after distant thermal ablation or irradiation. In this study, we therefore assessed systemic and local immune responses in individual patients treated with RFA.</p><p><bold>Methods:</bold> For this prospective clinical trial, patients with liver metastasis from colorectal carcinoma (mCRC) receiving RFA and undergoing metachronous liver surgery for another lesion were recruited (<italic>n</italic> = 9) during a 5-year period. Tumor and non-malignant liver tissue samples from six patients were investigated by whole transcriptome sequencing and tandem-mass spectrometry, characterizing naturally presented HLA ligands. Tumor antigen-derived HLA-restricted peptides were selected by different predefined approaches. Further, candidate HLA ligands were manually curated. Peripheral blood mononuclear cells were stimulated <italic>in vitro</italic> with epitope candidate peptides, and functional T cell responses were assessed by intracellular cytokine staining. Immunohistochemical markers were additionally investigated in surgically resected mCRC from patients treated with (<italic>n</italic> = 9) or without RFA (<italic>n</italic> = 7).</p><p><bold>Results:</bold> In all six investigated patients, either induced immune responses and/or pre-existing T cell immunity against the selected targets were observed. Multi-cytokine responses were <italic>inter alia</italic> directed against known tumor antigens such as cyclin D1 but also against a (predicted) mutation contained in ERBB3. Immunohistochemistry did not show a relevant influx of immune cells into distant malignant lesions after RFA treatment (<italic>n</italic> = 9) as compared to the surgery only mCRC group (<italic>n</italic> = 7).</p><p><bold>Conclusions:</bold> Using an individualized approach for target selection, RFA induced and/or boosted T cell responses specific for individual tumor antigens were more frequently detectable as compared to previously published observations with well-characterized tumor antigens. However, the witnessed modest RFA-induced immunological effects alone may not be sufficient for the rejection of established tumors. Therefore, these findings warrant further clinical investigation including the assessment of RFA combination therapies e.g., with immune stimulatory agents, cancer vaccination, and/or immune checkpoint inhibitors.</p>