Deferoxamine Increases Breast Cancer Radiosensitivity

Objective: Radiotherapy reduces the risk of breast cancer recurrence by destroying residual cancer cells post-surgery. The detrimental effect of radiation on surrounding tissues, however, significantly increases complications including reconstructive failure during both autologous and implant-based breast reconstruction.¹ Pharmacologic treatments aimed at mitigating radiation-induced injury have the potential to improve outcomes among these patients. Specifically, recent studies in our laboratory suggest deferoxamine (DFO) is capable of reducing skin ulceration and collagen fibril disorganization following radiation. What remains unclear, however, is whether breast cancer cells are concomitantly protected, a factor that would worsen cancer-specific outcomes among patients undergoing reconstruction. The purpose of this study is to determine the impact of DFO delivered in combination with XRT on breast cancer cell proliferation to ensure that tumor growth will not be concomitantly enhanced given the obvious improvements in skin viability resulting from DFO treatment.

Methods: Two triple-negative breast cancer cell lines, MDA-MB-231 and MDA-MB-468, were obtained from the University of Michigan Comprehensive Cancer Center and grown in culture. The dose-dependent effect of XRT (0, 5, and 10Gy) and DFO (0, 25, 50, 75, and 100µM) on proliferation of each cell line was determined via hemocytometer. Then, the radiosensitivity of these cell lines was determined at 10Gy of XRT and increasing doses of DFO. All three experiments were replicated via an MTS assay, a colorimetric assay for assessing cell metabolic activity, to fortify the results. All experiments were performed in triplicate. Statistical analysis was performed at p<0.05 significance using SPSS.

Results: Cell number significantly decreased in both MDA-MB-231 (171x10⁴ to 86x10⁴, p=0.00) and MDA-MB-468 (145x10⁴ to 31x10⁴, p=0.00) cells following exposure to 5Gy of XRT. Surprisingly, cell number also significantly decreased in response to 25µM DFO (MDA-MB-231: 171x10⁴ to 34x10⁴, p=0.00; MDA-MB-468: 145x10⁴ to 13x10⁴, p=0.04). The sensitivity of both triple-negative breast cancer cell lines to 10Gy of XRT increased with the delivery of DFO, as evidenced by the significant decrease in cell number at 100µM DFO compared to 0µM DFO (p=0.00, p=0.00). Percent viability, which was quantitatively determined utilizing an MTS assay, significantly decreased in both cell lines in response to 10Gy XRT (MDA-MB-231: 100% to 77%, p=0.00; MDA-MB-468: 100% to 76%, p=0.04) and 25µM DFO (MDA-MB-231: 100% to 84%, p=0.00; MDA-MB-468: 100% to 56%, p=0.00) administered independently. Finally, 100µM DFO increased the sensitivity of MDA-MB-231 (100% to 90%, p=0.01) and MDA-MB-468 (100% to 71%, p=0.04) cells to 10Gy XRT.

Conclusion: XRT and DFO significantly decreased breast cancer cell proliferation when delivered independently and in combination. In a complementary fashion to previously published studies on iron chelation and cancer proliferation,² this study provides evidence that DFO may be safely utilized to facilitate improved surgical, aesthetic, and quality of life outcomes without increasing tumorigenesis among patients with triple-negative breast cancer.

1. Kronowitz  SJ, Robb GL. Breast reconstruction with  post mastectomy  radiation therapy: current issues. Plast Reconstr Surg 2004;114(4):950-60.
2. Mertens C, Akam EA, Rehwald C, Brüne B, Tomat E, Jung M. Intracellular iron chelation modulates the macrophage iron phenotype with consequences on tumor progression. PLoS One 2016;11(11):e0166164.