Molecular Assessment of HER2 to Identify Signatures Associated with Therapy Response in HER2-Positive Breast Cancer

Simple Summary

The HER2 status of breast cancers is accurately determined by measuring HER2 protein overexpression and gene amplification. However, these clinical diagnostic tests cannot predict the response to therapy. Single molecule imaging approaches can quantify molecular features of HER2, such as receptor nano-organization, with exquisite spatial resolution and sensitivity. The aim of our study was to assess how the molecular features of HER2 varied with the therapy response. According to our results in cultured cell lines and six patient specimens, the therapy response was associated with high detected HER2 densities and clustering. This advanced imaging approach can thus provide key data to complement the current diagnostic standards.

Abstract

Trastuzumab, the prototype HER2-directed therapy, has markedly improved survival for women with HER2-positive breast cancers. However, only 40–60% of women with HER2-positive breast cancers achieve a complete pathological response to chemotherapy combined with HER2-directed therapy. The current diagnostic assays have poor positive-predictive accuracy in identifying therapy-responsive breast cancers. Here, we deployed quantitative single molecule localization microscopy to assess the molecular features of HER2 in a therapy-responsive setting. Using fluorescently labeled trastuzumab as a probe, we first compared the molecular features of HER2 in trastuzumab-sensitive (BT-474 and SK-BR-3) and trastuzumab-resistant (BT-474^R and JIMT-1) cultured cell lines. Trastuzumab-sensitive cells had significantly higher detected HER2 densities and clustering. We then evaluated HER2 in pre-treatment core biopsies from women with breast cancer undergoing neoadjuvant therapy. A complete pathological response was associated with a high detected HER2 density and significant HER2 clustering. These results established the nano-organization of HER2 as a potential signature of therapy-responsive disease.

Single molecule characterization of individual extracellular vesicles from pancreatic cancer

Biofluid-accessible extracellular vesicles (EVs) may represent a new means to improve the sensitivity and specificity of detecting disease. However, current methods to isolate EVs encounter challenges when they are used to select specific populations. Moreover, it has been difficult to comprehensively characterize heterogeneous EV populations at the single vesicle level. Here, we robustly assessed heterogeneous EV populations from cultured cell lines via nanoparticle tracking analysis, proteomics, transcriptomics, transmission electron microscopy, and quantitative single molecule localization microscopy (qSMLM). Using qSMLM, we quantified the size and biomarker content of individual EVs. We applied qSMLM to patient plasma samples and identified a pancreatic cancer-enriched EV population. Our goal is to advance single molecule characterization of EVs for early disease detection.

Abbreviations: EV: Extracellular Vesicle; qSMLM: quantitative Single Molecule Localization Microscopy; PDAC: Pancreatic Ductal Adenocarcinoma; EGFR: epidermal growth factor receptor 1; CA19-9: carbohydrate antigen 19-9; SEC: size exclusion chromatography; WGA: wheat germ agglutinin; AF647: Alexa Fluor 647; Ab: antibody; HPDEC: Healthy Pancreatic Ductal Epithelial Cell; TEM: Transmission Electron Microscopy.