TY - JOUR
T1 - The impact of 5-formyltetrahydrofolate on the anti-tumor activity of pralatrexate, as compared to methotrexate, in HeLa cells in vitro
AU - Visentin, Michele
AU - Unal, Ersin Selcuk
AU - Goldman, I. David
N1 - Funding Information:
Acknowledgments this study was supported by a grant from Spectrum Pharmaceuticals, Inc (Irvine, Ca).
PY - 2014/5
Y1 - 2014/5
N2 - Purpose: To investigate the impact of 5-formyltetrahydrofolate on the activities of pralatrexate, as compared to methotrexate (MTX), in vitro. Methods: Cells were exposed to (6S)5-formyltetrahydrofolate (5-formylTHF) for 24 h, before or after a 6-h exposure to antifolates following which the cellular accumulation and activities of the drugs were evaluated in HeLa cells. Results: A 24-h delay between a 6-h exposure to antifolates and a subsequent 24-h exposure to 4 μM 5-formylTHF sustained the full activities of both antifolates. A 72-h interval was required between a single exposure of up to 4 μM 5-formylTHF and subsequent exposure to drugs to sustain activities of the antifolates. When cells were incubated with 4 μM 5-formylTHF for 24 h weekly, for 4 weeks, there was no significant increase in the IC50 for pralatrexate, but the MTX IC50 increased 2.5-fold as compared to cells growing continuously in 25 nM 5-formylTHF. This cyclical exposure to 5-formylTHF increased the cell folate pool by 16 %, had no significant effect on the intracellular pralatrexate level, but decreased intracellular MTX by 15 %. An extracellular concentration of MTX 50-fold higher than that of pralatrexate was required to achieve an intracellular level, and growth inhibition, comparable to that of pralatrexate. Conclusions: Cyclical exposures to 5-formylTHF at levels in excess of what is achieved in most clinical "rescue" regimens do not affect pralatrexate accumulation nor antitumor activity in HeLa cells, in contrast to MTX. An important element in preserving pralatrexate activity is achieving a sufficient interval between exposure to 5-formylTHF and the next dose of antifolate.
AB - Purpose: To investigate the impact of 5-formyltetrahydrofolate on the activities of pralatrexate, as compared to methotrexate (MTX), in vitro. Methods: Cells were exposed to (6S)5-formyltetrahydrofolate (5-formylTHF) for 24 h, before or after a 6-h exposure to antifolates following which the cellular accumulation and activities of the drugs were evaluated in HeLa cells. Results: A 24-h delay between a 6-h exposure to antifolates and a subsequent 24-h exposure to 4 μM 5-formylTHF sustained the full activities of both antifolates. A 72-h interval was required between a single exposure of up to 4 μM 5-formylTHF and subsequent exposure to drugs to sustain activities of the antifolates. When cells were incubated with 4 μM 5-formylTHF for 24 h weekly, for 4 weeks, there was no significant increase in the IC50 for pralatrexate, but the MTX IC50 increased 2.5-fold as compared to cells growing continuously in 25 nM 5-formylTHF. This cyclical exposure to 5-formylTHF increased the cell folate pool by 16 %, had no significant effect on the intracellular pralatrexate level, but decreased intracellular MTX by 15 %. An extracellular concentration of MTX 50-fold higher than that of pralatrexate was required to achieve an intracellular level, and growth inhibition, comparable to that of pralatrexate. Conclusions: Cyclical exposures to 5-formylTHF at levels in excess of what is achieved in most clinical "rescue" regimens do not affect pralatrexate accumulation nor antitumor activity in HeLa cells, in contrast to MTX. An important element in preserving pralatrexate activity is achieving a sufficient interval between exposure to 5-formylTHF and the next dose of antifolate.
KW - (6S)5-formyltetrahydrofolate
KW - 5- Formyltetrahydrofolate
KW - Folylpolyglutamate synthetase
KW - Leucovorin
KW - Methotrexate
KW - Pralatrexate
KW - Reduced folate carrier
KW - Rescue
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U2 - 10.1007/s00280-014-2441-9
DO - 10.1007/s00280-014-2441-9
M3 - Article
C2 - 24682532
AN - SCOPUS:84900792195
SN - 0344-5704
VL - 73
SP - 1055
EP - 1062
JO - Cancer Chemotherapy and Pharmacology
JF - Cancer Chemotherapy and Pharmacology
IS - 5
ER -