Reinforcement of cancer immunotherapy by adoptive transfer of cblb‐deficient CD8⁺ T cells combined with a DC vaccine

Abstract

The success of cancer immunotherapy is limited by potent endogenous immune-evasion mechanisms, which are at least in part mediated by transforming growth factor-b (TGF-b). The E3 ubiquitin ligase Cbl-b is a key regulator of T cell activation and is established to regulate TGF-b sensitivity. cblb-deficient animals reject tumors via CD8 + T cells, which make Cbl-b an ideal target for improvement of adoptive T-cell transfer (ATC) therapy. In this study, we show that cblb-deficient CD8 + T cells are hyper-responsive to T-cell receptor (TCR)/CD28-stimulation and are in part protected against the negative cues induced by TGF-b in vitro. Notably, adoptive transfer of polyclonal, non-TCR transgenic cblb-deficient CD8 + T cells is not sufficient to reject B16-ova or EG7 tumors in vivo. Thus, cblb-deficient ATC requires proper in vivo re-activation by a dendritic cell (DC) vaccine. In strict contrast to ATC monotherapy, this approach delayed tumor outgrowth and significantly increased survival rates, which is paralleled by increased CD8 + T-cells infiltration to the tumor site and enrichment of ova-specific and interferon-c (IFN-c)-secreting CD8 + T cell in the draining lymph node (LN). Moreover, CD8 + T cells from cblb-deficient mice vaccinated with the DC vaccine show increased cytolytic activity in vivo. In summary, our data using cblb-deficient polyclonal, non-TCR-transgenic adoptively transferred CD8 + T cells into immuno-competent non-lymphodepleted recipients suggest that targeting Cbl-b might serve as a novel 'adjuvant approach', suitable to augment the effectiveness of established anti-cancer immunotherapies.

Modulation of Immune Cell Functions by the E3 Ligase Cbl-b

“…Nevertheless, ACT of polyclonal cblb -deficient CD8 + T cells into immunocompetent wild-type mice yielded contradictory results. While Chiang et al showed that ACT of cblb -deficient CD8 + T cells into EG.7 tumor-bearing C57Bl/6 wt mice led to delayed tumor outgrowth or even eradication of established tumors (72), we found that sole ACT of polyclonal cblb -deficient CD8 + T cells in immunocompetent wildtype mice challenged with either EG.7 lymphoma or B16.ova melanoma, was not sufficient to significantly delay tumor growth (74). In contrast to other reports (92–95), we did not transfer TCR transgenic tumor-antigen specific but polyclonal T cells.…”

“…Vaccination with tumor antigen-pulsed DCs thereby provide a second stimulus leading to an efficient accumulation and in vivo selection of tumor antigen-specific CD8 + T cells. Our data indicate that cblb targeting in T cells alone is not sufficient to counteract cancer-associated immune suppression, but that reactivation of the engineered T cells by a DC vaccine induces a profound anti-tumor immune response in non-TCR-transgenic mice (74). …”

“…Moreover, we used immunocompetent wildtype recipient mice and did not combine the ACT with induction of lymphopenia as often approached (92). As monotherapy with cblb -deficient polyclonal CD8 + T cells did not provoke any benefit in neither B16.ova melanoma nor EG.7 lymphoma injected immunocompetent mice in our hands, we established a combination therapy of ACT of cblb- deficient CD8 + T cells and DC vaccination, resulting in delayed tumor outgrowth and significantly prolonged survival rates when DC vaccination was combined with ACT of cblb- deficient instead of wt CD8 + T cells (74). The enhanced anti-tumor activity was accompanied by a significantly higher CD8 + T cell infiltration into the tumor and significantly increased numbers of tumor-antigen-positive OVA-specific CD8 + T cells as well as IFN-γ secreting cells in the tumor draining lymph node.…”

A phase I clinical trial combining dendritic cell vaccination with adoptive T cell transfer in patients with stage IV melanoma

“…Lutz-Nicoladoni et al [27] as well as Koike et al [26] showed delayed tumor outgrowth or better survival and tumor regression as a result of this combination treatment in >40 % of animals inoculated with aggressive tumors. Song et al [29] as well as Tamai et al [30] had similar findings and showed that combination treatment led to T cell infiltration into the primary tumor, as well as into metastases and induced immunological memory that protected the mice from re-challenge.…”

“…Studies from several mouse models have suggested that the combination of DC vaccination with ACT is superior to single agent treatments [26][27][28][29][30]. Lutz-Nicoladoni et al [27] as well as Koike et al [26] showed delayed tumor outgrowth or better survival and tumor regression as a result of this combination treatment in >40 % of animals inoculated with aggressive tumors.…”