The cancer cells showed a dose‐dependent increase in the expression of calreticulin, as well as the release of heat shock protein 70 (HSP70) and high mobility group box 1 (HMGB1) (Figures 1C,D; S1B,C, Supporting Information), which are widely accepted immunogenic markers that define ICD.[24] Based on these results, optimum verteporfin dosage to induce adequate ICD without severely affecting cell viability was selected for subsequent experiments (20 ng mL−1 for E.G7‐OVA and 200 ng mL−1 for MOC2 and 4T1 cells). Here, HMGB1 is linked to cancer.