Abstract 1810: Three-dimensional microtissues as phenotypic screening model to identify radiation modifiers for breast cancer

Abstract

Abstract Among breast cancer patients, radiation therapy resistance is a common problem in treatment. Overcoming the mechanisms responsible for this phenotype is an ongoing challenge. Options include repurposing established chemotherapeutics and the discovery of new radiosensitizing compounds. Three-dimensional (3D) microtissue models offer a physiological environment for efficient preclinical drug testing. We have adopted the 3D microtissue technology (Insphero, AG) to generate highly reproducible mammary cancer microtissues in a 96 well format. Two breast cancer cell lines (T47D and MDA-MB-361) were shown to be able to form 3D spheroids and grow in a reproducible manner over time. Validation of the phenotypic screen using breast cancer 3D microtissues was performed by HER2_shRNA knockdown, exposure to ionizing radiation and a panel of selected chemotherapeutic compounds. HER2_shRNA knockdown and irradiation decelerated growth, as proven by measuring the area of the cell spheroids after treatment. Of ten analyzed chemotherapeutics, vinblastine was the most effective compound, with docetaxel and doxorubicine being less effective in combination with radiation. To investigate the response in a model closer to the in vivo situation we investigated the response of heterotypic 3D microtissues containing both fibroblasts and breast cancer cells. Drug treatment of these heterotypic 3D cultures confirmed treatment with radiation plus vinblastine to be additive in causing breast cancer growth inhibition. Additionally a histological method to embed 3D microtissues in paraffin was established. The expression of the proliferation marker Ki67 and the apoptosis marker active Caspase 3 was evaluated in MDA-MB-361 cells after irradiation and concurrent vinblastine treatment. Such combined treatment caused prominent 3D microtissue damage - defined as extensive staining of active Caspase 3 and less Ki67. This suggests that combining vinblastine and radiation may be an effective radiation sensitizing strategy. Citation Format: Natasa Anastasov, Ines Höfig, Vanja Radulovic, Sabine Richter, Jan Lichtenberg, Jens M. Kelm, Christian Thirion, Michael J. Atkinson. Three-dimensional microtissues as phenotypic screening model to identify radiation modifiers for breast cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1810. doi:10.1158/1538-7445.AM2015-1810