Role of the Radiosensitizing Effect of Metformin Added to Concomitant Chemoradiotherapy with Cisplatin in Cervical Squamous Cell Cancer Cell Lines

Abstract

<h3>Purpose/Objective(s)</h3> The aim of this study is to investigate the radiosensitizing effect of metformin per se and combined with cisplatin in human cervical cancer cell lines (HeLa) and explore how radiosensitizing effect changes with activation/inhibition of adenosine monophosphate-activated protein kinase (AMPK). <h3>Materials/Methods</h3> AMPK gene expressions were compared between normal cervix and cervical cancer tissues using GSE9750 and GSE63514 databases. HeLa cell lines were exposed to 0, 2, 4, 6, and 8 Gy ionizing radiation (IR), 150 uM metformin, 1 uM cisplatin, 100 uM A769662 (AMPK activator), and 0.5 uM dorsomorfin (AMPK inhibitor) or combination of those drugs with cisplatin and IR. Cell proliferation, western blotting, and flow cytometry were used to evaluate the treatment effects. <h3>Results</h3> AMPK gene (PRKAA1) expressions were significantly higher in cervical cancer tissues than normal cervical tissue. Metformin and cisplatin per se did not decrease the cell proliferation without IR, but metformin, when combined with cisplatin, potentiated cisplatin cytotoxicity. Although the radiosensitizing effects of metformin and cisplatin per se were present which is more apparent in high (4, 6, and 8 Gy) IR doses, metformin-cisplatin combinations did not increase the radiosensitivity of cisplatin in any IR doses. Dorsomorfin per se significantly decreased cell proliferation and when combined with cisplatin potentiated radiosensitizing effect of cisplatin in 0, 2, 4, and 6 Gy IR doses, and this effect was confirmed with an increase in p-53BP1 and ERCC1 protein levels. Thus, dorsomorfin was found to be a better radiosensitizing agent than A769662 and metformin. Administration of A769662 one day prior to cisplatin treatment resulted in increased AMPK level that produced resistance to cisplatin, but this effect was not observed in HeLa cells when concomitantly treated with A769662 and cisplatin. The radiosensitizing effects of metformin, cisplatin, A769662, and dorsomorfin have been confirmed with the analysis of DNA damage proteins, damage repair proteins and evaluation of cell cycle arrest. <h3>Conclusion</h3> Modulation of AMPK may have a role in cervical cancer treatment. Increased AMPK levels result in higher sensitivity to IR but cause resistance to cisplatin. Dorsomorfin is a potent radiosensitizing agent and further clinical trials should be performed. The use of metformin alone may be an option as a radiosensitizer during high dose IR (e.g., intracavitary brachytherapy) in clinical practice and further clinical trials should be performed.