Figures & data
Figure 1. Effects of MTX on AH130 cell recruitment to S. (A) Effects of different concentrations of MTX added at time zero on 14C-thymidine incorporation (R) in the 90-minute interval between 16.5 and 18 hours of incubation; R values (DPM incorporated per 106 viable cells in 90 minutes), representing a measure of DNA synthesis, are means ± SEM of 3 independent experiments; dashed line: untreated control. (B) Effects of the treatment or not (ctr/light gray) with 1 μM (1000 nM) or 10nM MTX on R (determined under the above conditions) in the presence of (ctr/hatched) MTX alone or (dark gray) MTX plus 50μM folate (F), dihydrofolate (FH2) or tetrahydrofolate (FH4); values are means ± SEM of 10 independent experiments. (C) Effects of the treatment or not (ctr) with 10nM MTX plus 50μM F on the percentage of labeled cells (autoradiography) following a 90 minute incubation in the presence of 3H-thymidine from 16.5 to 18 hours of incubation; the time zero value in the absence of treatment is also shown (incubation with 3H-thymidine from time 0 to 90 minutes); values are means ± SEM of 3 independent experiments. Significance of differences was evaluated by the Student's t test for paired samples (**p < 0.02; ***p < 0.001).
Figure 2. Effects of MTX and/or F on the inhibition of AH130 cell recruitment to S by pyruvate or antimycin A. R values (DPM 14C-thymidine incorporated per 106 viable cells in the interval 16.5–18 h of incubation) were determined in the absence (dashed line) or the presence of 10 mM pyruvate (light gray) or 6 μM antimycin A (dark gray), without (ctr) or with 10 nM MTX and/or 50 μM F, and are means ± SEM of 5 independent experiments. Significance of differences was evaluated by the Student's t test for paired samples (*p < 0.05; **p < 0.02).
Figure 3. Effects of aminoacids involved in folate metabolism on AH130 cell recruitment to S. R values (DPM 14C-thymidine incorporated per 106 viable cells in the interval 16.5–18 h of incubation) were determined in the presence or the absence of aminoacids and/or MTX added at time 0. (A) Effects of 5mM serine, glycine, aspartic acid or glutamic acid (ctr: untreated control). (B) Effects of different serine concentrations; values are expressed as Δ% of untreated control (0). (C) Effects of 2.5mM serine (light gray), MTX (hatched) or serine plus MTX (dark gray); untreated control: dashed line. Values are means ± SEM of 3 independent experiments. Significance of differences was evaluated by the Student's t test for paired samples (*p < 0.05; **p < 0.02).
Figure 4. Pathways linking folate metabolism, MTX action and serine/glycine interconversions. See text for explanation. Notes: (a) the level of action of the most important drugs interfering with folate metabolism is shown; (b) the enzymatic activity of MTHFD the acronym refers to (methylenetetrahydrofolate-dehydrogenase) is NADP-dependent; (c) MS exhibits N5-methylTHF:homocysteine-methyltransferase activity; (d) pathways 1 are cytosolic, 2 cytosolic or mitochondrial, 3 mitochondrial; (e) arrows point to the product(s) of enzymatic reaction; (f) ┤ inhibitory action.
