Rapid plasma membrane reorganisation and endocytosis in HER2 breast cancer cells incubated with trastuzumab decorated polymer nanoparticles

Abstract

Knowledge on HER2+ breast cancer biology has informed drug design leading to targeted therapies giving improved clinical outcomes. Drug resistance and disease relapse, however still drive a continuous need for more efficacious and reliable therapeutics. Nanoparticles (NPs) as HER2 targeting nanomedicines offer new hope for selective targeting of HER2 within and beyond solid tumours, together with concomitant delivery of therapeutic cargo. For initial preclinical characterisation, studies on NP endocytosis and drug delivery are often performed in HER2+ breast cancer cell models, but information on initial NP-HER2 dynamics at the plasma membrane and how this impacts endocytic uptake and delivery efficiency is largely missing. Here using polymer poly(lactic-co-glycolide) acid NPs decorated with different valencies of the HER2 targeting monoclonal antibody trastuzumab, we have designed approaches to immediately study the impact of NP-HER2 targeting on high and low HER2 expressing breast cancer cell models. Using resonant scanning confocal imaging of live cell plasma membrane dynamics, we show in very high detail and within 10 minutes of cell exposure of the receptor to the NPs, extensive blebbing and ruffling of the plasma membrane, manifesting before much longer uptake of the NPs into the cell interior. Plasma membrane reorganisation was rapidly reversible, with cells reaching baseline morphology in 30 minutes. Our findings were confirmed at the ultrastructural level by scanning electron microscopy in cells fixed within 10 and 30 minutes of exposure to the NPs. Endocytic traffic of the NPs was in part directed to lysosomes and we discover a relationship between antibody valency and the ability of the NPs to deliver the chemotherapeutic agent doxorubicin to mediate cell death. Knowledge gained from these studies offers new approaches to study NP-cell dynamics in different NP-receptor settings and how receptor targeting influences plasma membrane organisation, endocytosis and delivery.