Irradiation of necrotic cancer cells, employed for pulsing dendritic cells (DCs), potentiates DC vaccine-induced antitumor immunity against high-grade glioma

Abstract

Dendritic cell (DC)-based immunotherapy has yielded promising results against high-grade glioma (HGG). However, the efficacy of DC vaccines is abated by HGG-induced immunosuppression and lack of attention toward the immunogenicity of the tumor lysate/cells used for pulsing DCs. A literature analysis of DC vaccination clinical trials in HGG patients delineated the following two most predominantly applied methods for tumor lysate preparation: freeze-thaw (FT)-induced necrosis or FT-necrosis followed by X-ray irradiation. However, from the available clinical evidence, it is unclear which of both methodologies has superior immunogenic potential. Using an orthotopic HGG murine model (GL261-C57BL/6), we observed that prophylactic vaccination with DCs pulsed with irradiated FT-necrotic cells (compared to FT-necrotic cells only) prolonged overall survival by increasing tumor rejection in glioma-challenged mice. This was associated, both in prophylactic and curative vaccination setups, with an increase in brain-infiltrating Th1 cells and cytotoxic T lymphocytes (CTL), paralleled by a reduced accumulation of regulatory T cells, tumor-associated macrophages (TAM) and myeloid-derived suppressor cells (MDSC). Further analysis showed that irradiation treatment of FT-necrotic cells considerably increased the levels of carbonylated proteins — a surrogate-marker of oxidation-associated molecular patterns (OAMPs). Through further application of antioxidants and hydrogen peroxide, we found a striking correlation between the amount of lysate-associated protein carbonylation/OAMPs and DC vaccine-mediated tumor rejection capacity thereby suggesting for the first time a role for protein carbonylation/OAMPs in at least partially mediating antitumor immunity. Together, these data strongly advocate the use of protein oxidation-inducing modalities like irradiation for increasing the immunogenicity of tumor lysate/cells used for pulsing DC vaccines.

Pathogen response-like recruitment and activation of neutrophils by sterile immunogenic dying cells drives neutrophil-mediated residual cell killing

“…Tolerogenic apoptosis was induced by TUN (TUN, 50 μg/ml; Enzo Lifesciences, Farmingdale, NY, USA or SigmaAldrich, St. Louis, MO, USA) or cisplatin (CDDP, 100 μM; Sigma-Aldrich). Immunogenic apoptosis was induced by MTX (MTX, 2 μM; Sigma, Bornem, Belgium), radiotherapy (120 Gy, performed as described previously) 9,33 or Hypericinbased PDT (Hyp-PDT; incubation with 200 nM Hypericin, for 2 h in serum-free media, followed by light irradiation of 2.70 J/cm 2 performed as described previously). 17 Hypericin was prepared, purified and stored as detailed elsewhere.…”

Immunogenic versus tolerogenic phagocytosis during anticancer therapy: mechanisms and clinical translation

“…108 However, while some physicochemical strategies can induce ICD (e.g., radiotherapy, PDT) yet certain others cannot (e.g., freeze/thawing-based necrosis). 1,52,59,109 In the latter cases, exogenous addition of recombinant immunogenic 'eat me' signals (such as recombinant CRT) 52,56,64,110,111 can complement immunogenic phagocytosis (Figure 3b). In line with this, several studies have used recombinant CRT to augment the immunogenicity of otherwise low immunogenic cancer vaccines (Figure 3b), 52,56,64,110,111 or to promote the immunogenic potential of cancer cells treated with loco-regionally applied chemotherapeutics, such as melphalan.…”

Tumour and normal tissue radiobiology in mouse models: how close are mice to mini-humans?

“…As an example, in a preclinical model of dendritic vaccination in a mouse glioblastoma model, the ratio between the T-lymphocyte subtypes type 1 helper (TH1), regulatory (Treg) and type 17 helper (TH17) were significantly related to survival. 44 In human glioblastoma, only the TH17-associated metagene was related to the prognosis. In order to increase the translation ability of the preclinical model to males, only effects on TH17 should be considered relevant and optimized instead of obscuring the preclinical model by including non-relevant parameters for the human condition (Table 1).…”