Table 1.

Colony-Forming Efficiency (%)^* in Soft Agar of Ntv-a Brain Cultures Infected with RCAS Vectors.

RCAS Vector	Genetic Background
	Ptc+/+	Ptc+/-
MYC	1.7	8.0
β-catenin	0.3	2.4
MTA†	25	33
uninfected	0.3	1.4
LACZ	0	0

^*Colony-forming efficiency={[number of colonies÷(number of colonies+single cells)]x100}.

^†MTA — polyomavirus middle T antigen.