FIG. 4.

Tumors from Tax transgenic mice are resistant to irradiation-induced apoptosis. Tumor-derived cell lines (F8 and SC) (A) and fresh tumor cells from Tax transgenic mice (B) were either mock treated (middle column) or exposed to 2,000 rads of γ-irradiation (right column). Five hours later, cells were stained with FITC-conjugated antibodies to annexin V to measure apoptosis. A wild-type p53-containing cell line (204-3-1) and normal mouse splenocytes (Ctrl Spleen) were used as positive controls. The apoptosis-resistant cells consist of the larger, more numerous cells present in spleen and tumor tissue from Tax transgenic mice and absent in normal mouse spleens (compare scatter plots; left).