Dendritic cell vaccines based on immunogenic cell death elicit danger signals and T cell–driven rejection of high-grade glioma

Abstract

The promise of dendritic cell (DC)-based immunotherapy has been established by two decades of translational research. Of the four malignancies most targeted with clinical DC immunotherapy, high-grade glioma (HGG) has shown the highest susceptibility. HGG-induced immunosuppression is a roadblock to immunotherapy, but may be overcome by the application of T helper 1 (T(H)1) immunity-biased, next-generation, DC immunotherapy. To this end, we combined DC immunotherapy with immunogenic cell death (ICD; a modality shown to induce T(H)1 immunity) induced by hypericin-based photodynamic therapy. In an orthotopic HGG mouse model involving prophylactic/curative setups, both biologically and clinically relevant versions of ICD-based DC vaccines provided strong anti-HGG survival benefit. We found that the ability of DC vaccines to elicit HGG rejection was significantly blunted if cancer cell-associated reactive oxygen species and emanating danger signals were blocked either singly or concomitantly, showing hierarchical effect on immunogenicity, or if DCs, DC-associated MyD88 signal, or the adaptive immune system (especially CD8(+) T cells) were depleted. In a curative setting, ICD-based DC vaccines synergized with standard-of-care chemotherapy (temozolomide) to increase survival of HGG-bearing mice by ~300%, resulting in ~50% long-term survivors. Additionally, DC vaccines also induced an immunostimulatory shift in the brain immune contexture from regulatory T cells to T(H)1/cytotoxic T lymphocyte/T(H)17 cells. Analysis of the The Cancer Genome Atlas glioblastoma cohort confirmed that increased intratumor prevalence of T(H)1/cytotoxic T lymphocyte/T(H)17 cells linked genetic signatures was associated with good patient prognosis. Therefore, pending final preclinical checks, ICD-based vaccines can be clinically translated for glioma treatment.

Preclinical efficacy of immune-checkpoint monotherapy does not recapitulate corresponding biomarkers-based clinical predictions in glioblastoma

“…1,2 GBM is resistant to most existing multimodal therapies. [3][4][5] Nearly 160 FDA-approved anti-GBM drugs have been applied, yet only a few are implemented as standard-of-care (e.g., temozolomide, since 2005). 2 Current GBM treatment paradigm consists of maximal surgical resection followed by radiotherapy plus temozolomide.…”

In Vitro Generation of Murine Dendritic Cells for Cancer Immunotherapy: An Optimized Protocol

“…This finding is an important stepping stone on which to build an effective combination strategy of DC immunotherapy with other immunomodulatory agents, such as checkpoint inhibitors, chemotherapeutics, Toll-like receptor-agonists (TLR), etc. Hyp-PDT DC immunotherapy has been shown to be efficient in a therapeutic setting in a model of high-grade glioma, when sequentially combining vaccination with temozolomide-based tumor regression (25).…”

“…Thereafter the cells were thawed, suspended in Dulbecco's phosphate-buffered saline (DPBS, Lonza) and exposed to Hyp-PDT treatment. For Hyp-PDT based elicitation of immunogenic cell death, the cells were incubated with 1 μM hypericin [prepared, purified and stored as detailed elsewhere (12)] for 2 h in DPBS followed by light irradiation (4.05 J/cm 2 ) performed as described previously (8,12,20). Cells were recovered 4 h post-treatment.…”

“…Thereafter the cells were exposed to three cycles of freeze-thawing to ensure 100% devitalization of cells i.e. no live cells within the lysate (8).…”

Caspase-2 and oxidative stress underlie the immunogenic potential of high hydrostatic pressure-induced cancer cell death

“…It has been long hypothesized that most anticancer therapies induce poorly immunogenic or even tolerogenic cancer cell death. 1 However, accumulating evidence indicates that in response to certain chemotherapeutics (e.g., anthracyclines, mitoxantrone, oxaliplatin, or bortezomib), 2,3 ionizing irradiation, 4 oncolytic viruses, 5,6 and Hypericin-based photodynamic therapy (Hyp-PDT), 7,8 tumor cells can undergo an immunogenic form of apoptosis called "immunogenic cell death" (ICD) inducing an effective antitumor immune response in immunocompetent mice compared with vaccination of immunodeficient mice. 9,10 These findings demonstrate the important role of the immune system in the efficacy of anticancer therapy.…”