In vitro radiosensitization by eribulin in human cancer cell lines.

Background: The objective was to to determine the radiosensitizing properties of eribulin and the potential mechanisms of radiosensitization in cervical (HeLa) and pharyngeal (FaDu) cancer cell lines. Materials and methods: Cytotoxicity was evaluated by the crystal violet method. The 10% and 50% inhibitory concentration (IC10, IC50) for 24-hour drug exposure were determined. The surviving fraction at 2 Gy (SF2) and the sensitizer enhancement ratio (SER) were calculated from radiation cell survival curves in the presence or absence of eribulin. Combination index (CI) was calculated to determine if there is a true synergistic interaction between eribulin and irradiation. Cell cycle changes were assessed by propidium iodide staining and flow cytometry. Apoptotic cells were detected by annexin V and TUNEL-assay. Results: Mean IC50s and IC10s were 1.58 nM and 0.7 nM and 0.7 nM and 0.27 nM for HeLa and FaDu cells, respectively. Radiosensitization was observed in both lines with a SER up to 2.71 and 2.32 for HeLa and FaDu cells, respectively. A true synergistic effect was showed with a CI of 0.82 and 0.76 for HeLa and FaDu cells, respectively. Eribulin induced significant G2/M cell arrest and marked apoptosis. Irradiation combined with 3 nM eribulin increased the apoptotic response to radiation in Hela cells. Conclusion: Eribulin shows a true in vitro radiosensitizing effect in HeLa and FaDu cells by inducing significant G2/M phase arrest. In HeLa, the enhancement radiation-induced apoptosis could be an additional mechanism of radiosensitization. Further studies are needed to evaluate the clinical benefits of concurrent eribulin and radiotherapy as a novel therapeutic strategy for cancer.