Figure 1.

T-DM1 induces ICD markers in T-DM1–sensitive breast cancer cells and ICD correlates with T-DM1 sensitivity in patients. A, Western blot analysis of mitotic arrest [p-H3 (S10)], apoptosis (cleaved caspase-3 and PARP), and ICD marker [p-eIF2α (S51)] in T-DM1–treated SK-BR-3 WT (left) and BT-474 WT (right) cells. B and C, Relative ATP release (B) and HMGB1 release (C) from T-DM1–treated SK-BR-3 WT and BT-474 WT cells (n = 3, 4). D, Immunofluorescence cell-surface staining of calreticulin (green) in T-DM1–treated SK-BR-3 WT cells. Scale bar, 10 μm. DAPI was used to stain the nucleus. Its quantification is provided on the right. E, Cytokine array blot analysis showing the differentially secreted cytokines in T-DM1–treated SK-BR-3 WT cells. F, Schematic summary of the treatment scheme and the sample collection timeline in GSE194040 (22). G, Heatmap of ICD-related genes found in the ICD gene signature score (33) and their correlation with pCR in T-DM1 + pertuzumab-treated patients from GSE194040. pCR: 1, sensitive; pCR: 0, resistant. Chi-square analysis of sensitive vs. resistant tumors expressing low vs. high ICD score is provided below. H, Percentage of CD8⁺ cells in sensitive (sens) vs. resistant (res) tumors collected pre- (n = 40) and post-T-DM1 (n = 18) treatment. Tables of the percentages of CD8-low or CD8-high tumors (based on average levels of CD8⁺ cells in each group) are given below and significance was calculated using Chi-square test. I, The representative images from H. Scale bar, 150 μm. Data correspond to mean values ± SD. P values for the bar graphs were calculated with the unpaired, two-tailed Student t test. Significance for the Chi-square analysis was calculated with the Chi-square test. **, P < 0.01. (F, Created with BioRender.com.)