Gene Modification of Breast Cancer Cells for Cancer Imaging

Abstract

Human epidermal growth factor receptor 2 (HER2) is a prominent breast cancer cell surface receptor that is overexpressed in approximately 20-30% of breast cancer tumours. Trastuzumab (Herceptin) is an effective clinical treatment against HER2-positive breast cancer, but ineffective against HER2-negative breast cancer. Current imaging methods may not be adequate to detect heterogenous HER2 expression in breast cancer tumours. MARS molecular CT is a new whole-body imaging technology that has potential to detect this variability non-invasively. This study aimed to produce genetically modified murine breast cancer cells that over-express human HER2 protein to develop a preclinical HER2-positive animal model to assess the potential of MARS molecular CT in measuring HER2 protein expression in tumours non-invasively. Murine breast cancer cell lines EO771 and Py230 were genetically modified using lipid-based transfection technology and DNA plasmid vectors encoding the full-length human HER2. Stable transfectants were selected via a selection marker co-expressed in the plasmid vectors. HER2 protein expression in the modified cancer cells were analysed by western blot analysis. HER2 protein localisation was visualised using immunofluorescence and compared to human HER2-positive human breast cancer cells (SkBr3) and parental non-transfected murine breast cancer cells. The optimised transfection protocol for the murine breast cancer cell lines resulted in up to 67% of EO771 and 56% of Py230 cells transfected. This optimised transfection protocol allowed the production of a series of gene-modified clones that showed varying levels of HER protein expression and cellular localization. Overall, this project has produced murine breast cancer cells that express the human HER2 protein. These HER2 modified cell lines will be used to develop a mouse model of HER2-positive breast cancer that will be used to assess the potential of MARS imaging technology in measuring HER2 protein expression in vivo.