Cancer 2013 July-15

 

Adoptive transfer of siRNA Cblb-silenced CD8+ T lymphocytes augments tumor vaccine efficacy in a B16 melanoma model.

PLoS One. 2012;7(9):e44295.

Hinterleitner R, Gruber T, Pfeifhofer-Obermair C, Lutz-Nicoladoni C, Tzankov A, Schuster M, Penninger JM, Loibner H, Lametschwandtner G, Wolf D, Baier G.

Department of Pharmacology and Genetics, Medical University Innsbruck, Innsbruck, Austria.

Abstract

The ubiquitin ligase Cbl-b is an established regulator of T cell immune response thresholds. We recently showed that adoptive cell transfer (ACT) of cblb(-/-) CD8(+) T cells enhances dendritic cell (DC) immunization-mediated anti-tumor effects in immune-competent recipients. However, translation of cblb targeting to clinically applicable concepts requires that inhibition of cblb activity be transient and reversible. Here we provide experimental evidence that inhibition of cblb using chemically synthesized siRNA has such potential. Silencing cblb expression by ex vivo siRNA transfection of polyclonal CD8(+) T cells prior to ACT increased T cell tumor infiltration, significantly delayed tumor outgrowth, and increased survival rates of tumor-bearing mice. As shown by ex vivo recall assays, cblb silencing resulted in significant augmentation of intratumoral T cell cytokine response. ACT of cblb-silenced polyclonal CD8(+) T cells combined with DC-based tumor vaccines predominantly mediated anti-tumor immune responses, whereas no signs of autoimmunity could be detected. Importantly, CBLB silencing in human CD8(+) T cells mirrored the effects observed for cblb-silenced and cblb-deficient murine T cells. Our data validate the concept of enhanced anti-tumor immunity by repetitive ACT of ex vivo cblb siRNA-silenced hyper-reactive CD8(+) T cells as add-on adjuvant therapy to augment the efficacy of existing cancer immunotherapy regimens in clinical practice.

PMID: 22962608

 

Supplementary information:

In the rapid development of novel Cancer Immunotherapies in the last years, specific Blockade of Immune Checkpoints has emerged as key strategy. In contrast to cell surface molecules like CTLA-4 and PD-1, Cbl-b is located inside the cell and serves as an intracellular signaling checkpoint. Cbl-b has key roles in limiting T, NKT and B cell activation and therefore is an excellent target to interfere with tumor-related immune anergy and enhance the anti-tumor immune response.

Based on previous findings of our groups and others, that genetically cblb deficient mice are able to immunologically reject otherwise lethal tumor burdens, we have shown in this study that a transient abrogation of Cbl-b is sufficient to enhance anti-tumor immune responses in a therapeutical setting.

As a next step, a similar Cbl-b silencing protocol with human lymphocytes was set-up as a GMP-compliant procedure, where the patient`s own immune cells will be Cbl-b silenced ex vivo and re-administered as a patient-specific cellular therapy. Currently, Apeiron is preparing a first clinical trial together with the Cleveland Clinic Foundation which is planned to start later this year.

As another consequence of this study, an alternative approach has been initiated to identify low molecular weight compounds that selectively interfere with Cbl-b function. For this initiative, Apeiron is collaborating with Evotec AG, joining both companies expertise in immunology and drug discovery to develop an entirely novel class of cancer immunotherapeutics.

Guenther Lametschwandtner-1

Modified from Oncoimmunology. 2013 Feb 1;2(2):e22893. PMID: 23525844

 

 

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