This analysis of the tumors excised from mice was performed using a Zeiss LSM 710 system (Carl Zeiss), as described before (15 (link)). The primary and secondary antibodies for this experiment are listed in table S5. Apoptotic cells were detected by a standard TUNEL assay using the DeadEnd Fluorometric TUNEL System (Promega). In the fluorescence images acquired from each tissue sample, the fluorescence intensity and number of positively stained cells were quantified using the ImageJ software and presented as relative staining (%) compared to that of the PBS-treated control.