Cells were harvested using non-enzymatic cell dissociation solution (Sigma-Aldrich), suspended in 0.76% low melting point agar diluted 1:1 with 26 complete Waymouth medium (Sigma-Aldrich) and seeded in 6 well plates (10 4 cells/well) coated with 2 mls of 1.25% low melting point agar (Sigma-Aldrich) diluted 1:1 with 26 complete Waymouth medium. Plates were incubated at 37uC for three weeks and analyzed microscopically to identify anchorage independent clones. Colony size was determined from digital micrographs using Image-Pro Plus 5.0 software (Media Cybernetics, Inc., Bethesda, MD) to determine the average area calculated from measurements made on a total of 15-30 colonies.