Abstract:The expression "immunogenic cell death" (ICD) refers to a functionally unique form of cell death that facilitates (instead of suppressing) a T cell-dependent immune response specific for dead cell-derived antigens. ICD critically relies on the activation of adaptive responses in dying cells, culminating with the exposure or secretion of immunostimulatory molecules commonly referred to as "damage-associated molecular patterns". Only a few agents can elicit bona fide ICD, including some clinically established ch… Show more
“…These results confirm that starvation can mediate immunostimulatory effects. 9,19,20 However, they do not resolve the question whether autophagy and its modulation by DMKG impact the cancer cells or the immune system of the host.10.1080/2162402X.2018.1498285-F0001Figure 1. Nutrient deprivation improves tumor vaccination efficacy in an autophagy dependent manner. (A) .…”
The success of chemotherapy largely depends on the anticancer immune response triggered by tumor cells that succumb to immunogenic cell death (ICD). One of the hallmarks of ICD is premortem autophagy that facilitates the release of adenosine triphosphate from dying cancer cells and acts as a chemoattractant for dendritic cell precursors. Here, we show that the immune response induced by inoculation of cancer cells undergoing ICD in response to the anthracycline mitoxantrone (MTX) can be improved by a short-term fasting regimen (48 hours of starvation) and that this effect is reversed by systemic administration of the autophagy inhibitor dimethyl α-ketoglutarate. Tumor growth reduction by MTX treatment is known to depend on autophagy induction in cancer cells as well as on an intact immune system. We compared the antitumor effects of MTX on autophagy-competent cancers implanted in wild type (WT) or partially autophagy-deficient (Becn1± or Atg4b−/-) mice. While there was no difference in the tumor growth reducing effects of MTX on tumors evolving in WT, Becn1+/- and Atg4b−/- mice, we observed an increase in the toxicity of MTX on Atg4b−/- mice. These results suggest that autophagy in cancer cells (but less so in host cells) is rate-limiting for therapeutically relevant anticancer immune responses, yet has a major role in blunting the life-threatening toxicity of chemotherapy.
“…These results confirm that starvation can mediate immunostimulatory effects. 9,19,20 However, they do not resolve the question whether autophagy and its modulation by DMKG impact the cancer cells or the immune system of the host.10.1080/2162402X.2018.1498285-F0001Figure 1. Nutrient deprivation improves tumor vaccination efficacy in an autophagy dependent manner. (A) .…”
The success of chemotherapy largely depends on the anticancer immune response triggered by tumor cells that succumb to immunogenic cell death (ICD). One of the hallmarks of ICD is premortem autophagy that facilitates the release of adenosine triphosphate from dying cancer cells and acts as a chemoattractant for dendritic cell precursors. Here, we show that the immune response induced by inoculation of cancer cells undergoing ICD in response to the anthracycline mitoxantrone (MTX) can be improved by a short-term fasting regimen (48 hours of starvation) and that this effect is reversed by systemic administration of the autophagy inhibitor dimethyl α-ketoglutarate. Tumor growth reduction by MTX treatment is known to depend on autophagy induction in cancer cells as well as on an intact immune system. We compared the antitumor effects of MTX on autophagy-competent cancers implanted in wild type (WT) or partially autophagy-deficient (Becn1± or Atg4b−/-) mice. While there was no difference in the tumor growth reducing effects of MTX on tumors evolving in WT, Becn1+/- and Atg4b−/- mice, we observed an increase in the toxicity of MTX on Atg4b−/- mice. These results suggest that autophagy in cancer cells (but less so in host cells) is rate-limiting for therapeutically relevant anticancer immune responses, yet has a major role in blunting the life-threatening toxicity of chemotherapy.
“…DAMPs can be secreted extracellularly or exposed on the plasma membrane of a damaged cell. In a series of reviews by Garg et al, the authors described how PDT-generated DAMPs play a crucial role in the development of antitumor immunity (72)(73)(74)(75)(76)(77)(78)(79)(80). PDT-generated DAMPs include ecto-calreticulin, heat-shock protein 90 (HSP90), HSP70, extracellular ATP and HMGB1 (71,72).…”
Section: Immunogenic Cell Death (Icd) and Release Of Dampsmentioning
Photodynamic therapy (PDT) is a potentially immunogenic and FDA‐approved antitumor treatment modality that utilizes the spatiotemporal combination of a photosensitizer, light and oftentimes oxygen, to generate therapeutic cytotoxic molecules. Certain photosensitizers under specific conditions, including ones in clinical practice, have been shown to elicit an immune response following photoillumination. When localized within tumor tissue, photogenerated cytotoxic molecules can lead to immunogenic cell death (ICD) of tumor cells, which release damage‐associated molecular patterns and tumor‐specific antigens. Subsequently, the T‐lymphocyte (T cell)–mediated adaptive immune system can become activated. Activated T cells then disseminate into systemic circulation and can eliminate primary and metastatic tumors. In this review, we will detail the multistage cascade of events following PDT of solid tumors that ultimately lead to the activation of an antitumor immune response. More specifically, we connect the fundamentals of photochemically induced ICD with a proposition on potential mechanisms for PDT enhancement of the adaptive antitumor response. We postulate a hypothesis that during the course of the immune stimulation process, PDT also enriches the T‐cell repertoire with tumor‐reactive activated T cells, diversifying their tumor‐specific targets and eliciting a more expansive and rigorous antitumor response. The implications of such a process are likely to impact the outcomes of rational combinations with immune checkpoint blockade, warranting investigations into T‐cell diversity as a previously understudied and potentially transformative paradigm in antitumor photodynamic immunotherapy.
“…Collectively, these DAMP recruit antigen‐presenting cells (APC) to ICD sites and stimulate the uptake, processing, and presentation of dead‐cell‐associated antigens, resulting in an adaptive immune response . However, DAMP release is not sufficient to determine whether a molecule will induce ICD; thus, in vivo vaccination experiments are the gold standard to identify ICD inducers …”
Section: Introductionmentioning
confidence: 99%
“…1,[16][17][18] However, DAMP release is not sufficient to determine whether a molecule will induce ICD; thus, in vivo vaccination experiments are the gold standard to identify ICD inducers. 19,20 A subset of chemotherapeutic agents including doxorubicin, mitoxantrone, oxaliplatin, bortezomib, cyclophosphamide, and anthracycline have the ability to trigger ICD, 18,21 hence activating anticancer immune responses. 1 These drugs are used to treat different types of cancer, including hematological malignancies such as acute lymphoblastic leukemia (ALL).…”
T‐cell acute lymphoblastic leukemia (T‐ALL) has a poor prognosis derived from its genetic heterogeneity, which translates to a high chemoresistance. Recently, our workgroup designed thrombospondin‐1‐derived CD47 agonist peptides and demonstrated their ability to induce cell death in chronic lymphocytic leukemia. Encouraged by these promising results, we evaluated cell death induced by PKHB1 (the first‐described serum‐stable CD47‐agonist peptide) on CEM and MOLT‐4 human cell lines (T‐ALL) and on one T‐murine tumor lymphoblast cell‐line (L5178Y‐R), also assessing caspase and calcium dependency and mitochondrial membrane potential. Additionally, we evaluated selectivity for cancer cell lines by analyzing cell death and viability of human and murine non‐tumor cells after CD47 activation. In vivo, we determined that PKHB1‐treatment in mice bearing the L5178Y‐R cell line increased leukocyte cell count in peripheral blood and lymphoid organs while recruiting leukocytes to the tumor site. To analyze whether CD47 activation induced immunogenic cell death (ICD), we evaluated damage‐associated molecular patterns (DAMP) exposure (calreticulin, CRT) and release (ATP, heat shock proteins 70 and 90, high‐mobility group box 1, CRT). Furthermore, we gave prophylactic antitumor vaccination, determining immunological memory. Our data indicate that PKHB1 induces caspase‐independent and calcium‐dependent cell death in leukemic cells while sparing non‐tumor murine and human cells. Moreover, our results show that PKHB1 can induce ICD in leukemic cells as it induces CRT exposure and DAMP release in vitro, and prophylactic vaccinations inhibit tumor establishment in vivo. Together, our results improve the knowledge of CD47 agonist peptides potential as therapeutic tools to treat leukemia.
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