Table 1.

Tumorigenicity assay

Genotype*	Tumorigenicity†	Tumor weight, g‡	Histology
WT (Vector)	0/6	NA	NA
WT (Ras)	0/6	NA	NA
p53−/− (Vector)	0/2	NA	NA
p53−/− (Ras)	4/4	0.27 ± 0.15	SCC§
ARF−/− (Vector)	0/5	NA	NA
ARF−/− (Ras)	5/5	0.9 ± 0.5	SCC§
ARF+/− (Ras)	3/3¶	0.86 ± 1.27	SCC¶

^*Primary skin keratinocytes were derived from wild-type (WT), ARF-null (ARF^−/−), ARF heterozygous (ARF^+/−), and p53-null (p53^−/−) mice and were infected with control vector (Vector) or H-rasV12 (Ras). 

^† Tumorigenicity is defined as the ratio between the number of tumors arising to the number of sites injected. Mice harboring tumors were examined for 3 weeks; mice that did not form tumors were examined for up to 3 months. 

^‡ Tumor weights were measured 3 weeks after injection of cells. 

^§ SCC, squamous cell carcinoma. 

^¶ Allele-specific PCR revealed loss of the remaining wild-type ARF allele in all tumors.