Inverse Correlation between Endoplasmic Reticulum Stress Intensity and Antitumor Immune Response with Ruthenium(II)-Based Photosensitizers for the Photodynamic Therapy of Head and Neck Squamous Cell Carcinoma

. These unexpected findings challenge the prevailing view that PDT-triggered apoptosis and ER stress are essential for ICD. Our study underscores the complexity of PDT-induced cell death balance and immunogenic signals and highlights the need to redefine ICD-inducing criteria for the rational design of next-generation PSs.