Anti-HER2-targeted therapies: effects on human in vitro blood-brain barrier models

Metastatic breast cancer is associated with very poor overall survival and a reduced quality of life. HER2-positive breast cancer forms brain metastases at the late stages. Established therapies such as trastuzumab, pertuzumab, trastuzumab/pertuzumab, lapatinib and tucatinib are widely used and are selectively toxic to HER2-positive breast cancer cell line. However, the effects of these therapies on the properties of the blood-brain barrier (BBB) remain unclear. We investigated this using an <i>in vitro</i> human BBB model derived from CD34⁺ cells differentiated into brain-like endothelial cells (BLECs) and hCMEC/D3 cell line. BLECs were treated with different concentrations of trastuzumab, pertuzumab, trastuzumab/pertuzumab, lapatinib or tucatinib for 24 h and 48 h. We measured cell viability, transendothelial electrical resistance (TEER), paracellular permeability to fluorescein and mRNA expression profiles. Most treatments showed no effect on cell viability, permeability and TEER of endothelial cells. While treatment of BLECs with lapatinib and tucatinib at low concentrations resulted in increased cell viability/metabolism, treatment with a higher concentration of 5 μg/mL resulted in toxic effects. These results were confirmed using another BBB <i>in vitro</i> model, hCMEC/D3. Treatment with trastuzumab and trastuzumab/pertuzumab resulted in changes in the mRNA expression of BBB marker genes encoding efflux pumps (P-gp (ABCB1)/BCRP (ABCG2)), the glucose transporter GLUT-1 (SLC2A1), tight junction proteins (occludin (OCLN)/claudin-5 (CLDN5)) and the pro-inflammatory chemokine CCL2. In conclusion, we demonstrate different time- and concentration-dependent effects of anti-HER2-targeted therapies for the treatment of advanced HER2-positive breast cancer on the BBB <i>in vitro</i>. Further experiments are required to assess the clinical relevance of our results.