TABLE 2

Endogenous dNTP pools in HCT116 and SW620 cells after incubation FdUrd

Exponentially growing HCT116 MLH1-wild-type and MLH1-inactivated cells were incubated with an IC₅₀ for FdUrd or left untreated (control). SW620 cells were left untreated or transduced with shRNA targeted to MLH1 mRNA or nonspecific (NS) shRNA. Four days after shRNA treatment, exponentially growing cells were incubated with an IC₅₀ of FdUrd or left untreated (control). dNTP pools were extracted and analyzed as described under Materials and Methods. The data are presented as a percentage of the corresponding control value and represent the mean ± S.D. from duplicate determinations. Control values (picomoles of dNTP per 10⁶ cells): HCT116 0-1 cells, dCTP: 3.43 ± 1.0, dTTP: 29.7 ± 3.0, dATP: 6.1 ± 1.1, dGTP: 2.05 ± 0.6 HCT116 1-2 cells, dCTP: 4.0 ± 1.7, dTTP: 32.9 ± 2.8, dATP: 6.7 ± 0.8, dGTP: 1.97 ± 0.4. SW620, dCTP: 3.67 ± 0.5, dTTP: 20.05 ± 1.3, dATP: 3.55 ± 0.2, dGTP: 0.85 ± 0.04. SW620 + NSshRNA, dCTP: 7.06 ± 0.6, dTTP: 37.6 ± 3.1, dATP: 8.1 ± 0.2, dGTP: 1.84 ± 0.1. SW620 + MLH1shRNA, dCTP: 5.73 ± 1.3, dTTP: 21.42 ± 0.8, dATP: 4.93 ± 0.4, dGTP: 1.54 ± 0.5.