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.

4-hydroxytamoxifen is an active metabolite of the drug Tamoxifen. Tamoxifen is the first endocrine therapy drug and one of the most prescribed to treat breast cancer since more than four decades. The therapeutic indication of Tamoxifen is the treatment of hormone-dependent breast cancers expressing estrogen receptor ⍺ (ER⍺), the target of Tamoxifen.

To assess the selectivity of 4-hydroxytamoxifen, we designed a 6-tissue co-culture system consisting of encapsulated ER⍺- breast cancer spheroids (HCC1395, red ; MDA-MB231, purple ; SK-BR3, orange) and encapsulated ER⍺+ breast cancer spheroids (MCF-7, green ; T47D, uncolored ; BT-474, blue), treated with 4-hydroxytamoxifen 5µM for 48h (Figure 1). A staining with LIVE/DEAD dyes was performed to measure the cytotoxicity induced by 4-hydroxytamoxifen. The colors of the capsules were used to independently and simultaneously measure the cytotoxic activity of 4-hydroxytamoxifen in the six tissue types of the co-culture (Figure 2).