Concentration of Fe(3+)-Triapine in BEAS-2B Cells.

William E Antholine,Charles R Myers

doi:10.3390/ijms20123062

William E Antholine, Charles R Myers

Open Access

https://doi.org/10.3390/ijms20123062

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Abstract

An electron paramagnetic resonance (EPR) method was used to determine the concentration of the antitumor agent Triapine in BEAS-2B cells when Triapine was bound to iron (Fe). Knowledge of the concentration of Fe-Triapine in tumor cells may be useful to adjust the administration of the drug or to adjust iron uptake in tumor cells. An EPR spectrum is obtained for Fe(3+)-Triapine, Fe(3+)(Tp)2+, in BEAS-2B cells after addition of Fe(3+)(Tp)2+. Detection of the low spin signal for Fe(3+)(Tp)2+ shows that the Fe(3+)(Tp)2+ complex is intact in these cells. It is proposed that Triapine acquires iron from transferrin in cells including tumor cells. Here, it is shown that iron from purified Fe-transferrin is transferred to Triapine after the addition of ascorbate. To our knowledge, this is the first time that the EPR method has been used to determine the concentration of an iron antitumor agent in cells.

Highlights

The treatment of locally advanced cervical cancer has been successful with a combination of radiation therapy, a weekly dose of cisplatin, and a three-times weekly dose of Triapine (Tp) [1,2]
An electron paramagnetic resonance (EPR) method was used to measure the concentration of Fe(3+)(Tp)2+ in BEAS-2B cells and to demonstrate the transfer of Fe from FeTf to Triapine to form Fe(3+)(Tp)2+. This EPR method measures the concentration of Fe(3+)(Tp)2+ and could be valuable for future studies that try to manipulate the formation of Fe-Triapine in cells
Following the addition of Fe(3+)(Tp)2+ to BEAS-2B cells, the clearest EPR lines for oxidized Fe(3+)(Tp)2+ that were separated from other lines in the spectrum are the lines with g = 2.19 and g = 2.15 (Figure 2)

Summary

Introduction

The treatment of locally advanced cervical cancer has been successful with a combination of radiation therapy, a weekly dose of cisplatin, and a three-times weekly dose of Triapine (Tp) [1,2]. The uptake of Fe-Triapine using the EPR method has already been reported for SW480 cells [9]. In this communication, we discuss the EPR method to quantitate Fe(3+)-Triapine in cells. An EPR method was used to measure the concentration of Fe(3+)(Tp)2+ in BEAS-2B cells and to demonstrate the transfer of Fe from FeTf to Triapine to form Fe(3+)(Tp)2+. This EPR method measures the concentration of Fe(3+)(Tp)2+ and could be valuable for future studies that try to manipulate the formation of Fe-Triapine in cells

Results and Discussion

Transfer of Fe from FeTf to Triapine

Additional Mechanism for Fe-Triapine: A Hypothesis

Sample Preparation

EPR Spectrometer