The role of cross-presenting dendritic cells in tumour progression and immunotherapy

Author: Gilfillan, Connie Bep

Date: 2017

Publisher: University of Otago

Type: Thesis

Link to this item using this URL: http://hdl.handle.net/10523/7296

University of Otago

Abstract

The recognition and eradication of cancer cells by the immune system is reliant on dendritic cells (DCs). DCs are professional antigen-presenting cells (APCs) that are integral for the initiation of an adaptive immune response targeted to eliminate cancer cells. DCs are capable of cross-presentation, a necessary function for priming of cytotoxic T lymphocyte (CTL) responses. Specialised DC subsets are reported to be superior at cross-presenting and have been implicated as crucial cells for CTL responses against tumour progression. However, DCs are often inactive in the presence of immune-suppressive tumours and require stimulation to become activated. Immunotherapy can be utilised to provide stimulatory factors that drive the activation of DCs and subsequent initiation of effective anti-tumour responses. The immunotherapies investigated in this thesis were poly I:C, a toll-like receptor (TLR) 3 ligand; and combination of the danger signal monosodium urate crystals (MSU) and a Mycobacterium (M.smegmatis) that provides pathogen-associated molecular patterns (PAMPs). Peritumoural treatments with immunotherapies were successful at slowing tumour growth and prolonging survival of mice bearing 4T1 murine mammary tumours and B16 melanoma tumours. To investigate the role of cross-presenting DCs in the efficacy of immunotherapies, a mouse model was used whereby specialist cross-presenting DCs can be deleted. CD8α+ and CD103+ cross-presenting DCs express the C-type lectin domain family 9 member A (Clec9A) and through administration of diphtheria toxin (DT) in Clec9A-DTR mice, successful depletion of CD8α+ and CD103+ DCs is achieved. MSU+M.smegmatis immunotherapy was dependent on Clec9A+ DCs for efficacy. Conversely, poly I:C immunotherapy remained successful in the absence of these cells, suggesting an effective T cell response can be induced in mice lacking specialist cross-presenting DCs. The antigen-specific T cell responses generated with poly I:C were investigated in basic leucine zipper ATF-like transcription factor 3 (BATF3) knockout (KO) mice, which are deficient in CD103+ DCs. In the absence of Batf3-dependent DCs, treatment with poly I:C immunotherapy still induced proliferation of antigen-specific CTLs that were capable of producing IFNγ; however, their ability to kill target cells was impaired. To identify DCs involved in the anti-tumour response initiated by poly I:C immunotherapy, DC subsets were examined for the ability to acquire and present antigen. CD8α+, CD103+, triple negative (TN), CD11b+ and monocyte-derived DCs (moDCs) were able to capture cell-associated tumour antigen. Furthermore, these DC subsets were able to acquire soluble ovalbumin (OVA), with CD11b+ DCs demonstrating the greatest uptake. Interestingly, moDCs were unable to induce antigen-specific T cell proliferation ex vivo, whereas the CD11b+ and CD11b- DCs were capable of stimulating T cell expansion. There is considerable interest in combining chemotherapy with immunotherapy, as chemotherapeutic agents are capable of inducing immunogenic cell death. Treatment of 4T1 tumours with doxorubucin successfully reduced tumour growth; however, combination of MSU+M.smegmatis immunotherapy with doxorubicin provided no additional benefit to single treatments. Conversely, combination of poly I:C immunotherapy with doxorubicin enhanced anti-tumour responses compared to either monotherapy. In summary, the findings from this thesis show that MSU+M.smegmatis immunotherapy requires CD8α+ and CD103+ DCs for efficacy, whereas poly I:C immunotherapy remains successful in their absence. This finding also emphasises the ability of multiple DC subsets to acquire and cross-present antigen, leading to successful induction of anti-tumour responses.

Subjects: immunology, dendritic, cells, immunotherapy, tumour

Citation: ["Gilfillan, C. B. (2017). The role of cross-presenting dendritic cells in tumour progression and immunotherapy (Thesis, Doctor of Philosophy). University of Otago. Retrieved from http://hdl.handle.net/10523/7296"]

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