Severe, but not mild heat-shock treatment induces immunogenic cell death in cancer cells

Abstract

The mechanisms of immunogenicity underlying mild heat-shock (mHS) treatment < 42°C of tumor cells are largely attributed to the action of heat-shock proteins; however, little is known about the immunogenicity of tumor cells undergoing severe cytotoxic heat-shock treatment (sHS > 43°C). Here, we found that sHS, but not mHS (42°C), induces immunogenic cell death in human cancer cell lines as defined by the induction of ER stress response and ROS generation, cell surface exposure of calreticulin, HSP70 and HSP90, decrease of cell surface CD47, release of ATP and HMGB1. Only sHS-treated tumor cells were efficiently killed and phagocytosed by dendritic cells (DCs), which was partially dependent on cell surface calreticulin. DCs loaded with mHS or sHS-treated tumor cells displayed similar level of maturation and stimulated IFNγ-producing CD8 T cells without any additional adjuvants . However, only DCs loaded with sHS-treated tumor cells stimulated antigen-specific CD4 T cells and induced higher CD8 T-cell activation and proliferation. sHS-treated murine cells also exposed calreticulin, HSP70 and HSP90 and activated higher DC maturation than mHS treated cells. Vaccination with sHS-treated tumor cells elicited protective immunity in mice. In this study, we defined specific conditions for the sHS treatment of human lung and ovarian tumor cells to arrive at optimal ratio between effective cell death, immunogenicity and content of tumor antigens for immunotherapeutic vaccine generation.

Consensus guidelines for the definition, detection and interpretation of immunogenic cell death

“…Open access the ubiquitin-specific peptidase inhibitor spautin-1, the antibiotic bleomycin, the protein phosphatase-2A inhibitor LB-100, the Chinese herbal medicine component shikonin and capsaicin [34][35][36][37][38] and (8) numerous physical interventions, encompassing various forms of ionizing radiation, extracorporeal photochemotherapy, hypericinbased photodynamic therapy (PDT), near-infrared photoimmunotherapy, high hydrostatic pressure, severe cytotoxic heat shock, nanopulse stimulation and electrohyperthermia. [39][40][41][42][43][44][45][46][47][48][49] Importantly, dose and administration schedules have a major impact on the ability of many of these agents to initiate productive ICD. [50][51][52] The aforementioned ICD inducers have been instrumental not only for identifying the molecular machinery that underlies the immunogenicity of some variants of RCD, 5 but also for elucidating the pathophysiological and therapeutic implications of the process.…”

Medical Gas Plasma Jet Technology Targets Murine Melanoma in an Immunogenic Fashion

“…[ 40 ] If apoptosis, however, occurs in a highly pro‐inflammatory context, T‐cell co‐stimulation by activated DCs drive antitumor responses critical in the inactivation of cancer cells. [ 41 ] CRT and heat‐shock proteins are two key immunological determinates in this context, [ 42–44 ] and our results underline their increased surface expression in the immunogenic treatment regimens mitoxantrone (MTX) and gas plasma treatment. This corroborates previous results using another plasma source.…”

Hyperthermia Targeting the Tumor Microenvironment Facilitates Immune Checkpoint Inhibitors

“…Specifically, phagocytosis of APCs is mainly enhanced by immunogenic "eat me" signals of DAMPs through receptor-mediated endocytosis via PRR. Moreover, hyperthermia represses the "do not eat me" signal through decreasing the expression of CD47 in the cell surface (53). In addition, hyperthermia can also inhibit tolerogenic "eat me" signals by transforming immature APCs and/or APCs exhibiting immunosuppressive phenotypes (M2 macrophages, N2 neutrophils, myeloid-derived suppressor cells) to a relatively mature one (54,55).…”