TABLE 1.

Transformation frequencies are similar in the different Ink/Arf locus knockout mice^a

Genotype	No. of primary transformants per 106 nucleated cells
	Expt 1	Expt 2
Ink4a/Arf−/−	59 ± 3.5	72 ± 3.1
Ink4a/Arf+/+	95 ± 4.5	28 ± 2.1
Arf−/−	54 ± 5.0	31 ± 2.5
Arf+/−	21 ± 1.9	23 ± 2.9
p16Ink4a−/−	162 ± 7.0	115 ± 5.0
p16Ink4a+/+	146 ± 4.0	159 ± 6.0

^aBone marrow cells were infected with matched titers of Ab-MLV-P120 and plated in agar; macroscopic colonies of primary transformants were counted 10 days later (33). One +/+ or heterozygous animal and one −/− animal were used in each experiment. The transformation frequencies for p19^Arf+/− mice are similar to those obtained for +/+ mice from the p19^Arf colony. The values given represent the average number of colonies obtained per 10⁶ nucleated bone marrow cells ± the standard error of the mean. In each experiment, at least 6 × 10⁶ cells were evaluated in 72 independently plated cultures. The same virus stock was used to compare +/+ and −/− mice of each genotype, but different virus stocks were used with different groups of mice. Uninfected cultures did not contain macroscopic colonies.