2.9. IHC Staining

TNBC cell xenograft tumor tissues were fixed in 10% neutral-buffered formalin and embedded in paraffin. The sections (5 μm thick) were deparaffinized in xylene for 2 min 3 times, rehydrated in graded alcohols for 1 min, and washed in distilled water. IHC staining was performed using the Lab Vision automated system (Thermo Fisher) through the MD Anderson Cancer Center Division of Surgery Histology Core. The slides were then incubated with anti-Ki-67 (#RM-9106, 1:100, Thermo Fisher), anti-pHER2 (#2243, 1:320, Cell Signaling), anti-HER2 (#APA342AA, Biocare Medical, Pacheco, CA, USA), anti-EGFR (#4267, 1:50, Cell Signaling), anti-pEGFR (#API300AA, Biocare Medical), anti-Bim (#2933, 1:200, Cell Signaling), and anti-cleaved poly(ADP-ribose) polymerase (PARP, #5625, 1:100, Cell Signaling). Immunostained slides were scanned using an Aperio AT2 slide scanner (Leica, Buffalo Grove, IL, USA) and captured at 20× magnification using ImageScope software (Leica Biosystems, Wetzlar, Germany). Then intensity was quantified by ImageJ software [19].