Immune responses contribute to the success of radiation therapy of solid tumours; however, the mechanism of triggering CD8+ T cell responses is poorly understood. Antigen cross-presentation from tumour cells by dendritic cells (DC) is a likely dominant mechanism to achieve CD8+ T cell stimulation. We established a cross-presentation model in prostate cancer in which DC present a naturally expressed oncofetal tumour antigen (5T4) from irradiated DU145 tumour cells to 5T4-specific T cells. Ionising radiation (12 Gy) caused G2/M cell cycle arrest and cell death, increased cellular 5T4 and high-mobility protein group-B1 (HMGB1) levels and upregulated surface calreticulin and Hsp70 expression in DU145 cells. Co-culture of DC with irradiated tumour cells lead to efficient phagocytosis of tumour cells and upregulation of CD86 and HLA-DR on DC. CD8+ 5T4-specific T cells, stimulated with these DC, proliferated and produced IFNγ. Inhibition of HMGB1 decreased T cell stimulation but not DC activation, while TRIF/MyD88 inhibition only had a marginal effect on T cell stimulation. Unlike previous reports, I found no functional evidence that DC with Asp299Gly toll-like receptor-4 (TLR4) single nucleotide polymorphism had impaired ability to cross-present tumour antigen. However, I observed a highly significant and robust prevention of antigen cross-presentation when tumour cells were pretreated with the novel Hsp70 inhibitor, VER 155008. The inhibitor also prevented CD86 upregulation on DC co-cultured with irradiated tumour cells. Together, the results in this thesis demonstrate that radiation induces immunologically relevant changes in tumour cells, which can trigger CD8+ T cell responses via a predominantly Hsp70-dependent antigen cross-presentation process.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:620122 |
| Date | January 2014 |
| Creators | Salimu, Josephine |
| Publisher | Cardiff University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://orca.cf.ac.uk/64217/ |
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