Figure 4

Thymidine kinase (TK1) expression and FTD incorporation in CD44⁺ CD133⁺ DLD-1 cells. (a) TK1 expression in CD44⁺ CD133⁺ cells. TK1 levels in DLD-1 cells and CD44⁺ CD133⁺ DLD-1 cells were assayed using qRT-PCR and normalized against GAPDH levels. Data points represent means ± SD of triplicate determinations; Student’s t-test, *P < 0.05. (b) Dot plot analysis of FTD incorporation into the genomic DNA of CD44⁺ CD133⁺ DLD^-1 spheres. CD44⁺CD133⁺ DLD-1 cells were cultured in the presence of 1 μM FTD or DMSO for 11 days in sphere-formation assay conditions and genomic DNA was purified. Purified DNA (1 ng) was denatured with an alkaline solution (0.1 N NaOH), spotted onto a Hybond-N⁺ membrane, and blotted with anti-BrdU antibodies.