Cross-Presentation of the Oncofetal Tumor Antigen 5T4 from Irradiated Prostate Cancer Cells—A Key Role for Heat-Shock Protein 70 and Receptor CD91

Abstract

Immune responses contribute to the success of radiotherapy of solid tumors; however, the mechanism of triggering CD8 þ T-cell responses is poorly understood. Antigen cross-presentation from tumor cells by dendritic cells (DC) is a likely dominant mechanism to achieve CD8 þ T-cell stimulation. We established a cross-presentation model in which DCs present a naturally expressed oncofetal tumor antigen (5T4) from irradiated DU145 prostate cancer cells to 5T4-specific T cells. The aim was to establish which immunogenic signals are important in radiation-induced cross-presentation. Radiation (12 Gy) caused G 2 -M cell-cycle arrest and cell death, increased cellular 5T4 levels, high-mobility protein group-B1 (HMGB1) release, and surface calreticulin and heat-shock protein-70 (Hsp70) expression in DU145 cells. DCs phagocytosed irradiated tumor cells efficiently, followed by upregulation of CD86 on phagocytic DCs. CD8 þ 5T4-specific T cells, stimulated with these DCs, proliferated and produced IFNg. Inhibition of HMGB1 or the TRIF/MyD88 pathway only had a partial effect on T-cell stimulation. Unlike previous investigators, we found no evidence that DCs carrying Asp299Gly Toll-like receptor-4 (TLR4) single-nucleotide polymorphism had impaired ability to cross-present tumor antigen. However, pretreatment of tumor cells with Hsp70 inhibitors resulted in a highly statistically significant and robust prevention of antigen cross-presentation and CD86 upregulation on DCs cocultured with irradiated tumor cells. Blocking the Hsp70 receptor CD91 also abolished cross-presentation. Together, the results from our study demonstrate that irradiation induces immunologically relevant changes in tumor cells, which can trigger CD8 þ T-cell responses via a predominantly Hsp70-dependent antigen cross-presentation process. Cancer Immunol Res; 3(6); 678-88. Ó2015 AACR.

Prostaglandin E2-mediated adenosinergic effects on CD14+cells: Self-amplifying immunosuppression in cancer

“…2.5£10 6 cells were incubated in 2 mL media overnight in the presence or absence of 12.5% sPE. Adenosine A 2A and A 2B receptor-inhibitors (200 nM each) were added to cells for 30 min followed by 200 nM AMP (01930, Sigma) for 30 min, and 200 ng/mL lipopolysaccharide (LPS; L4391 Sigma) for 1 h. Intracellular cytokine staining was performed as described 43 following 4 h incubation with Golgi Plug (55509) and Golgi Stop (554724, both BD-Biosciences). Fixed (00-82249) and permeabilized (00-8333-56, both Affymetrix) cells were labeled with CD14 and TNFa antibodies at room temperature for 30 min.…”

Dendritic Cells and Immunogenic Cancer Cell Death: A Combination for Improving Antitumor Immunity

“…The interaction of HSP90 with CD91 leads to the activation of DCs and it facilitates the tumor antigen cross-presentation to CTLs; in fact, the blockade of CD91 receptor completely abolishes T cell activation in cross-presentation experimental models [89]. Spisek et al showed that tumor cells that were treated with bortezomib (a proteasome inhibitor) present increased expression of HSP90, which induces the upregulation of the maturation-associated markers CD80, CD83, and CD86 on DCs [90].…”

Cancer stem cells as targets for immunotherapy

“…High‐dose radiation alone may eliminate CSCs/TICs, as early prostate and lung cancers can be cured by radiotherapy alone. It may happen partly via generating immunogenic cell death, which then initiates tumour antigen uptake and antigen cross‐presentation by DC . One could speculate whether radiation‐induced CSC death is also immunogenic and weather radiation would generate CSC/TIC‐specific effector and memory T‐cells, significantly contributing to an abscopal effect and subsequent protection from relapse.…”

“…It may happen partly via generating immunogenic cell death, which then initiates tumour antigen uptake and antigen cross-presentation by DC. 89 One could speculate whether radiation-induced CSC death is also immunogenic and weather radiation would generate CSC/TIC-specific effector and memory T-cells, significantly contributing to an abscopal effect and subsequent protection from relapse. Despite its obvious clinical importance, this question has not been studied previously.…”