Rose Bengal Acetate PhotoDynamic Therapy (RBAc-PDT) Induces Exposure and Release of Damage-Associated Molecular Patterns (DAMPs) in Human HeLa Cells

Abstract

The new concept of Immunogenic Cell Death (ICD), associated with Damage Associated Molecular Patterns (DAMPs) exposure and/or release, is recently becoming very appealing in cancer treatment. In this context, PhotoDynamic Therapy (PDT) can give rise to ICD and to immune response upon dead cells removal. The list of PhotoSensitizers (PSs) able to induce ICD is still short and includes Photofrin, Hypericin, Foscan and 5-ALA. The goal of the present work was to investigate if Rose Bengal Acetate (RBAc), a powerful PS able to trigger apoptosis and autophagy, enables photosensitized HeLa cells to expose and/or release pivotal DAMPs, i.e. ATP, HSP70, HSP90, HMGB1, and calreticulin (CRT), that characterize ICD. We found that apoptotic HeLa cells after RBAc-PDT exposed and released, early after the treatment, high amount of ATP, HSP70, HSP90 and CRT; the latter was distributed on the cell surface as uneven patches and co-exposed with ERp57. Conversely, autophagic HeLa cells after RBAc-PDT exposed and released HSP70, HSP90 but not CRT and ATP. Exposure and release of HSP70 and HSP90 were always higher on apoptotic than on autophagic cells. HMGB1 was released concomitantly to secondary necrosis (24 h after RBAc-PDT). Phagocytosis assay suggests that CRT is involved in removal of RBAc-PDT generated apoptotic HeLa cells. Altogether, our data suggest that RBAc has all the prerequisites (i.e. exposure and/or release of ATP, CRT, HSP70 and HSP90), that must be verified in future vaccination experiments, to be considered a good PS candidate to ignite ICD. We also showed tha CRT is involved in the clearance of RBAc photokilled HeLa cells. Interestingly, RBAc-PDT is the first cancer PDT protocol able to induce the translocation of HSP90 and plasma membrane co-exposure of CRT with ERp57.

Intralesional rose bengal in melanoma elicits tumor immunityviaactivation of dendritic cells by the release of high mobility group box 1

“…These data are consistent with the observation that HMGB1 was passively released from photosensitized HeLa cells treated with a rose bengal analog [39]. Pretreatment with rose bengal acetate led to apoptosis and autophagy and the secretion of HSP70, HSP90 and HMGB1.…”

Anti-tumor immunity of BAM-SiPc-mediated vascular photodynamic therapy in a BALB/c mouse model

“…[47][48][49] For example, PDT with Photofrin, Hypericin, and Rose Bengal acetate has been shown to trigger the expression of CRT on the tumor cell surface in vitro. 8,50,51 The present study demonstrated that BAM-SiPc-PDT could induce the expression of surface CRT on CT26 tumor cells, together with two other DAMPs, HSP70, and HSP90, in vitro (Figure 1b and c). These surface-exposed HSPs have been reported to augment anti-tumor immunity by assisting DCs in acquiring and presenting tumor-derived antigens.…”

New photosensitizers for photodynamic therapy

“…The introduction of heavy atoms into the rings, such as the halogen atoms bromine and iodine, increases the triplet yield of the molecule by facilitating intersystem crossing. Rose Bengal has a long history as a photoactive dye and has been explored for antimicrobial applications [44], tissue bonding applications [45] and anti-cancer applications [46]. …”