Table 2.

Endogenous dNTP pools in HCT116 and SW620 cells following incubation FdUrd.

			% control value
Cell Line	MLH1 Status	Time (h)	dCTP	dTTP	dATP	dGTP
HCT116 0–1	inactivated	4	101.5 ± 17.3	62.0 ± 9.5	136.1 ± 18.5	42.2 ± 6.6
		24	95.6 ± 46.2	233.7 ± 49.9	338.5 ± 91.6	122.0 ± 48.3
HCT116 1–2	wildtype	4	85.0 ± 7.1	56.5 ± 12.6	174.4 ± 14.9	41.6 ± 0.7
		24	33.4 ± 12.6	51.5 ± 0.5	71.2 ± 2.0	18.5 ± 0.4
SW620	wildtype	4	91.0 ± 1.9	10.14 ± 0.5	143.1 ± 9.6	18.2 ± 2.5
		24	283.4 ± 96.3	17.06 ± 1.5	524.6 ± 92.6	41.8 ± 7.5
SW620 + non-specific shRNA	Suppressed	4	91.4 ± 12.1	8.9 ± 0.5	161.3 ± 7.0	18.2 ± 4.2
		24	560.2 ± 77.1	24.9 ± 7.5	790.5 ± 38.9	89.1 ± 27.7
SW620 + MLH1 targeted shRNA	wildtype	4	87.1 ± 0.5	11.3 ± 0.8	152.1 ± 8.6	26.62 ± 9.2
		24	410.0 ± 17.0	22.27 ± 0.07	781.9 ± 76.0	46.75 ± 22.0

Exponentially growing HCT116 MLH1-wildtype 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 non-specific (NS) shRNA. Four days following shRNA treatment, exponentially growing cells were incubated with IC₅₀ for FdUrd or left untreated (control). dNTP pools were extracted and analyzed as described in “Materials and Methods”. The data are presented as a % of the corresponding control value and represent the mean ± SD from duplicate determinations. Control values (pmol dNTP/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.