Radiosensitization of HER2-positive breast cancer cell lines with trastuzumab

• Published in: Journal of clinical oncology Vol. 31; no. 15_suppl; p. e11501
• Main Authors: Demirci Alanyali, Senem, Bozkurt, Emir, Alanyali, Hilmi, Karaca, Burcak, Uslu, Ruchan
• Format: Journal Article
• Language: English
• Published: 20.05.2013
• ISSN: 0732-183X; 1527-7755
• DOI: 10.1200/jco.2013.31.15_suppl.e11501

Abstract only e11501 Background: HER2 is a member of the human epidermal growth factor (EGF) receptor family that is blocked by a monoclonal antibody, Trastuzumab (Herceptin). In daily clinical practice, Trastuzumab is being used concurrently with radiotherapy (RT) in breast cancer patients. Administration of Trastuzumab with RT appear to be safe in regard to cardiac morbidity and mortality in patients with relatively modest follow-up duration (less than 5 years). In this study we aimed to determine the possible interactions between RT and Trastuzumab in HER2 positive breast cancer cell line MDA-MB-453. Methods: MDA-MB-453 cells were treated with increased dose of Trastuzumab (10 – 200 µg/mL, 72 hours) and irradiation (0-8 Gy, 4 Gy/min, 48 hours). XTT (Roche) viability assay was used to measure the cytotoxicity of Trastuzumab, and trypan blue method was used to measure the cytotoxicity of irradiation. The sensitization of MDA-MB-453 cell lines was done by IC50 of Trastuzumab with 24 hours treatment followed by 6 and 8 Gy irradiation. Results: Cytotoxicity was increased in a dose and time dependent manner by Trastuzumab and irradiation treatment in MDA-MB-453 cell lines. IC50 values of Trastuzumab and irradiation were found to be 167 µg/mL and 8 Gy, at 48 hours, respectively.Cells were pretreated with IC25 and IC50 doses of Trastuzumab for 24 hours and then irradiated with 6 and 8 Gy doses. The cell viability at 24 and 48 hours were significantly decreased (p=0.0012) compared to single exposures (Trastuzumab or irradiation), indicating that Trastuzumab sensitizes HER2 positive breast cancer cells to irradiation. Conclusions: This preliminary study showed the sensitization effect of Trastuzumab to irradiation in HER2 positive breast cancer cells. Further studies are warranted for the optimal dosing and normal tissue toxicity of this combination.