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

## TL;DR

This study examines how anti-HER2 cancer drugs affect the blood-brain barrier in lab models, finding varied effects depending on drug type, concentration, and time.

## Contribution

The study is the first to systematically evaluate the effects of anti-HER2 therapies on blood-brain barrier properties using human in vitro models.

## Key findings

- Most anti-HER2 therapies did not significantly affect blood-brain barrier cell viability or permeability.
- Low concentrations of lapatinib and tucatinib increased endothelial cell viability, while higher concentrations were toxic.
- Trastuzumab and trastuzumab/pertuzumab altered mRNA expression of blood-brain barrier marker genes.

## Abstract

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 in vitro 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 in vitro 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 in vitro. Further experiments are required to assess the clinical relevance of our results.