Table 2.
Damage-associated molecular pattern molecules that may be released or exposed on the outer leaflet of dying tumor cells after photodynamic therapy
| DAMP | Function | Ref. |
|---|---|---|
| HSP60, HSP70, HSP90, gp96, GRP94, GRP78 | Molecular chaperones that normally reside in intracellular regions/organelles, but under stress they are exposed on the damaged cell surface and prime immunomodulatory processes | [11,21,22,112] |
| Calreticulin | Calcium binding protein located in intracellular regions/organelles (mostly in ER), but under stress its presence on the PM is augmented. On the PM it acts as “danger signal” and increases the immunogenicity of the dying cells | [11,112] |
| ATP | High-energy molecule, normally intracellular, but can be released by necrotic and apoptotic cells under particular stresses. Extracellular ATP has the ability to help in chemoattraction of immune cells | [12,112] |
| Phosphatidylserine | When cells are damaged/dying, phosphatidylserine is transposed from the inner to the outer leaflet and acts as an “eat me” signal by interacting with multiple immune cells receptors, mediating efficient phagocytosis and anti-inflammatory responses | [112,113] |
| High mobility group box-1 | Nuclear chromatin-binding protein; it has prominent cytokine-line properties and when released by dying cells tends to stimulate immune cells to produce various pro-inflammatory cytokines | [11,112] |
| Calgranulin family members (S100A8, S100A9, S100A12) | Calcium-binding proteins; when released by necrotic cells they act as “find me” signals attracting various immune cells and interacting with immune cell receptor (TLR4/RAGE) to induce the secretion of pro-inflammatory cytokines | [11,112,114] |
| Cross-linked dimer of ribosomal protein S19 | Constituent of small ribosomal subunit; when released by necrotic cells it acts as a chemotactic factor for attracting various immune cells | [11,112] |
DAMPs: Damage-associated molecular patterns; ER: Endoplasmatic reticulum; PM: Plasma membrane; HSP: Heat shock protein; GRP: Glucose-regulated protein; ATP: Adenosine triphosphate; TLR4: Toll-like receptor 4; RAGE: Receptor for advanced glycation end-products.