(A, B) Colonogenic assays were performed by adding increasing concentrations of pemetrexed to control wild-type (WT) 293A cells and HMCES knockout (HMCES KO) cells (A) and quantification of results were shown (B). Increasing numbers of cells were seeded with increasing concentrations of the compound to obtain optimal drug-dose response curve. Seeding density with respect to control is indicated below each image. The images shown are representative of three biological repeats, each performed in duplicate. (B) Data are presented as mean±s.e.m. and student's t-test was performed for statistical analysis (****, p<0.0001). 