HER-2 is proteolyzed by caspases in HER-2-overexpressing breast cancer
cells during the induction of apoptosis. A, HER-2-overexpressing
SKBR3 human breast cancer cells were treated with 2 μg/ml TRAIL and 1
μg/ml cycloheximide for 0-16 h with or without pretreatment with 50
μm Z-VAD-fmk for 1 h. HER-2 was detected by immunoblotting using
a HER-2 mAb that recognizes the carboxyl terminus. B, SKBR3 cells
were preincubated with 100 nm epoxomicin and 50 μm
Z-VAD-fmk for 1 h as indicated and then treated with 2 μg/ml TRAIL and 1
μg/ml cycloheximide for 0-16 h. C, SKBR3 cells were preincubated
with 100 nm epoxomicin and 50 μm Z-VAD-fmk for 1 h as
indicated and then treated with 200 μm etoposide for 0-16 h. In
A-C, the HER-2 cleavage products are indicated by arrows.
Apoptotic nuclei were scored at each time point in parallel experiments, and
the percentage of apoptotic cells is indicated.