Immunohistochemical Analysis of Tumor Samples

After tumor collection, tissue was processed for immunohistochemical analysis following our published procedures [49 (link),52 (link)]. Antigen detection was performed using the following antibodies: Ki67 (ab15580; Abcam, Cambridge, MA, USA), p21 (2947; Cell Signaling, Danvers, MA, USA), cleaved Casp-3 (9661, Cell Signaling), phospho-eIF2α (3398; Cell Signaling), DDIT3 (179823; Abcam), and HO-1 (ab13248; Abcam). Slides were scored manually using a 20 × objective. Average histologic scores (H-score) were calculated as previously reported [55 (link)]. Based on the percentage of cells staining with 3+ (strong), 2+ (moderate), 1+ (weak), or O (absent) intensity, an H-score (range 0–3) was calculated by summing the percentages of cells staining at each intensity multiplied by the weighted intensity of staining: H-score = (% weakly stained cells × 1) + (% moderately stained cells × 2) + (% strongly stained cells × 3).