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. Author manuscript; available in PMC: 2015 May 1.
Published in final edited form as: Cancer Chemother Pharmacol. 2014 Mar 29;73(5):1055–1062. doi: 10.1007/s00280-014-2441-9

Figure 4. Effect of 4 weekly exposures to 5-formylTHF on total intracellular folate and antifolate accumulation.

Figure 4

(Panel A) HeLa cells were grown for one week in GAT to deplete endogenous folates and then replated for 4 weeks in 25 nM [3H]5-formylTHF. Once a week for four weeks a portion of cells was treated for 24h with 4 μM [3H]5-formylTHF, another portion was maintained in 25 nM [3H]5-formylTHF. Seventy-two hours after the last exposure to [3H]5-formylTHF, total intracellular radioactivity was measured. (Panel B) HeLa cells were grown in 25 nM 5-formylTHF; once each week the cells were exposed for 24h to 4 μM 5-formylTHF. Control cell were maintained in 25 nM 5-formylTHF. Seventy-two hours after the last exposure to 5-formylTHF, the cells were exposed to 0.1 μM [3H]pralatrexate or 5 μM [3H]MTX for 6h and intracellular radioactivity measured. Cells were always washed after each manipulation. Data are the mean ± S.E.M from three independent experiments.