Trastuzumab (Herceptin) is a monoclonal antibody used to treat breast cancer and stomach cancer. It was the first targeted therapy to treat HER2-expressing cancers and it increases the overall survival of breast cancer patients by almost 40%. The high selectivity of Trastuzumab limits therapeutic indications to cancers expressing the HER2 receptor.

To evaluate the binding selectivity of Trastuzumab, we designed a 2-tissue co-culture system consisting of purple matrix-labelled HER2-high breast cancer spheroids (SK-BR3) and blue matrix-labeled HER2-negative breast cancer spheroids (HCC1395), treated with fluorescent green-Trastuzumab (Trastuzumab-FITC) (Figure 1). A live-cell imaging time-course was performed to measure the kinetic of the binding of Trastuzumab on spheroids. The colors of the capsules were used to independently and simultaneously measured the binding of Trastuzumab-FITC to the two tissue types.

• Specific binding of Trastuzumab-FITC to HER2-high breast cancer spheroids (SK-BR3) and no binding to HER2-negative breast cancer spheroids (Figure 2-3)
• Half of the maximal binding to HER2-high breast cancer spheroids after 85 minutes.

• Clifford A, Hudis MD. Trastuzumab – Mechanism of Action and Use in Clinical Practice. New England Journal of Medicine, 357:39-51 (2007).
• Dai X, Cheng H, Bai Z, Li J. Breast Cancer Cell Line Classification and Its Relevance with Breast Tumor Subtyping. Journal of Cancer, 8(16): 3131-3141 (2017).