Mechanisms and pharmacological modulation of photodynamic therapy-induced cell death

Photodynamic therapy (PDT) produces spatially confined oxidative injury that can engage multiple regulated and accidental cell death programs with distinct immunological consequences. However, the strength of evidence supporting individual death modalities in PDT is highly uneven, and pathway assignment is frequently confounded by nonspecific biomarkers, incomplete causal validation, and extrapolation from non-PDT models. This review integrates the molecular biology of PDT-induced cell death with damage-associated molecular pattern signaling, antitumor immunity, therapeutic pharmacology, and clinical translation. A 14-parameter, mechanism-centered evidence appraisal framework was applied to the PDT literature to distinguish direct photodynamic evidence from mechanistic plausibility, model context, pharmacological and genetic validation, exclusion of competing pathways, temporal resolution, immune function, translational relevance, and overall confidence. On this basis, ferroptosis, intrinsic and extrinsic apoptosis, pyroptosis, necroptosis, and accidental necrosis emerge as the comparatively best-supported PDT-associated death modalities, whereas paraptosis, anoikis, autophagy-dependent cell death, cuproptosis, parthanatos, mitochondrial permeability transition-driven necrosis, and oxeiptosis remain emerging or insufficiently corroborated. The review further examines how photosensitizer localization, photodynamic exposure, oxygenation, tumor biology, and pharmacological intervention bias pathway engagement and shape immunogenicity, while emphasizing that damage-associated molecular pattern release does not by itself establish productive antitumor immunity. PDT-induced cell death is therefore mechanistically steerable in experimental systems but presently only potentially tunable in patients, where pathway-specific biomarker validation remains limited. Collectively, this framework provides the PDT field with an evidence-weighted basis for experimental design, pathway attribution, biomarker selection, pharmacological combination strategies, and mechanism-informed clinical investigation.