Conventional amphotericin B elicits markers of immunogenic cell death on leukemic blasts, mediates immunostimulatory effects on phagocytic cells, and synergizes with PD-L1 blockade

Abstract

Immunostimulatory regimens are a game changer in the fight against cancer, but still only a minority of patients achieve clinical benefit. Combination with immunomodulatory drugs and agents converting otherwise non-immunogenic forms of cell death into bona fide “immunogenic cell death” (ICD) could improve the efficacy of these novel therapies. The aim of our study was to investigate conventional Amphotericin B (AmB) as an enhancer of antitumor immune responses. In tumor cell line models, AmB induced ICD with its typical hallmarks of calreticulin (CALR) expression and release of high mobility group box 1 (HMGB1) as well as Adenosine 5’-triphosphate (ATP). Interestingly, in contrast to non-ICD inducing treatments, ICD induction led to up-regulation of PD-L1-expression by ICD experiencing cells, resulting in decreased maturation of dendritic cells (DCs). Blocking this PD-L1 expression on tumor cells could unleash full ICD effects on antigen presenting cells. Even at sub-toxic concentrations, AmB was able to enhance CALR on leukemic blasts, particularly on phagocytic monoblastic THP-1 cells, which also showed features of “M1-like” differentiation after AmB exposure. The ability of AmB to increase the immunogenicity of tumor cells was confirmed in vivo in a mouse vaccination experiment. In conclusion, we demonstrate that AmB can promote antitumor immune responses in a dose-dependent manner by ICD induction, surface translocation of CALR on leukemic blasts even at sub-toxic concentrations, and “M1-like” polarization of phagocytic cells, making it noteworthy as potential booster for cancer immunotherapy. We additionally report for the first time that PD-L1 expression may be a feature of ICD, possibly as a negative feedback mechanism regulating the maturation status of DCs and thus indirectly affecting T-cell priming.

Immunogenic cell death in cancer: concept and therapeutic implications

“…The prototypic ICD-associated “eat-me” signal is CALR, an endoplasmic reticulum (ER) chaperone that is exposed on the outer leaflet of the plasma membrane downstream of the integrated stress response (ISR) and consequent phosphorylation of eukaryotic translation initiation factor 2 subunit alpha (EIF2S1, best known as eIF2α) [ 47 , 48 ]. Common immunostimulatory DAMPs mechanistically linked to ICD encompass ATP, which is actively secreted by an autophagy-dependent mechanism [ 49 ], as well as high mobility group box 1 (HMGB1) and annexin A1, both of which appear to be passively released upon nuclear and plasma membrane permeabilization [ 50 – 52 ]. Finally, type I interferon (IFN) and C-X-C motif chemokine ligand 10 (CXCL10) have been involved in multiple instances of ICD [ 53 , 54 ].…”

Effects of Electrochemotherapy on Immunologically Important Modifications in Tumor Cells

“…In our study, electrochemotherapy with all three tested chemotherapeutics induced ICD-associated DAMPs, but the induced DAMP signature was cell line and chemotherapeutic concentration specific. Some ICD-triggering regimens may also boost antigenicity through the modification of cell surface marker expression [ 25 , 34 , 37 , 38 ]. In our study, we showed that electrochemotherapy with CDDP, OXA or BLM can modify the expression of MHC I, MHC II, PD-L1 and CD40 cell surface markers.…”

“…Besides DAMPs, chemotherapeutics can also help upregulate antigen presentation and decrease tumor immune escape [ 25 , 36 ]. It was already shown that in some cancers CDDP can upregulate MHC I and PD-L1; OXA can upregulate MHC I and PD-L1; and BLM can upregulate PD-L1 [ 34 , 36 , 37 , 38 ].…”

An immunogenic cell death-related regulators classification patterns and immune microenvironment infiltration characterization in intracranial aneurysm based on machine learning

“…Additionally, photothermal therapy and the CDT-mediated ICD improve anti-tumor immunity by exposing HMGB1, CRT, and ATP. Reports also suggest Amphotericin B (AmB) enhances the anti-tumor immune response by releasing HMGB1, which induces ICD ( 29 ). Studies show a correlation between high serum concentration of IL-33 and inflammation, poor prognosis, and severity of aSAH.…”