Figure 5.

KO of SK1 protects p53 heterozygote mice from tumor development. (a) Pie chart representation of tumor burden found during necropsy and confirmed via histology of p53 heterozygote mice with the indicated SK1 genotype. (b) Kaplan-Meier survival analysis of p53 heterozygote mice with different SK1 genotypes. Each point represents a mouse that died naturally or was sacrificed due to tumor burden or unthriftiness, whereas the n listed includes mice that are still living, all of which contribute to the survival estimate curve. Differences between the survival curves are statistically significant (by log-rank comparison P < 0.02). (c) Spleens were harvested from mice of the indicated genotypes and phenotypes, homogenized, and submitted to lipid analysis. C₁₆-ceramide was measured by LC/MS. Data are averages of lipid levels determined for thymuses from three mice and are expressed as pmole lipid per mg protein ± SEM. Asterisk indicates a statistically significant difference (P < 0.05 by Student’s t test relative to the other groups). (d) Protein markers of cell cycle arrest and senescence. Spleens from mice of the indicated genotypes and phenotypes were homogenized, and equal amounts were examined by Western blotting.