Role of tumor biomechanics on drug-receptor engagement

/ Abstract Monoclonal antibody (mAb) therapies targeting the human epidermal growth factor receptor 2 (HER2) have transformed the treatment of HER2-positive breast cancer. However, many patients develop resistance or fail to achieve durable remission, underscoring the limitations of receptor abundance as a predictor of therapeutic response. Increasing evidence indicates that the tumor microenvironment (TME), particularly extracellular matrix (ECM) stiffness, collagen density, and vascular dysfunction, critically influence drug delivery, receptor accessibility, and binding kinetics. Stiff and poorly perfused regions create physical barriers that hinder the diffusion of large therapeutic antibodies such as trastuzumab (TZM), reducing effective delivery and HER2 engagement. The goal of this project is to investigate the mechanistic basis of antibody accessibility, receptor binding, and therapeutic efficacy in intact tumor tissues. Animal tumor models are required because antibody delivery, receptor-drug engagement, vascular perfusion, ECM stiffness, collagen organization, and cellular density are coupled properties of the intact tumor microenvironment that cannot be adequately reproduced in vitro. Xenograft and patient-derived xenograft models were selected to provide biologically relevant variation in receptor expression, collagen content, cellular density/distribution, and vascular organization. Applying the mesoscopic imaging platform to these excised tumor tissues will generate heterogeneous, spatially resolved datasets to test how tumor biomechanics and vasculature regulate drug–target engagement and support future translation to clinical tumor specimens. Our central hypothesis is that tumor biomechanical and vascular heterogeneity regulates antibody accessibility, HER2 binding, and therapeutic efficacy, and that pharmacologic modulation of ECM stiffness will influence antibody penetration and response. This hypothesis is supported by our preliminary findings showing that collagen-rich, poorly vascularized tumors exhibit markedly reduced TZM–HER2 engagement compared with more compliant, well-perfused tumors, even when HER2 expression is equivalent, demonstrating that TME biomechanics, not receptor levels alone, determine effective drug binding. Despite the clear impact of TME, no existing imaging platform can simultaneously quantify drug–target binding, biomechanical stiffness, and vascular features in intact, whole tumors. To address this critical gap, we will develop and apply mFLIO², a first-in-class multimodal imaging system that integrates mesoscopic fluorescence lifetime imaging Förster resonance energy transfer (mesoFLI-FRET), optical coherence tomography (OCT), and optical coherence elastography (OCE). This co-registered platform will provide quantitative maps of tumor molecular interactions, structural organization, and biomechanical properties within the same specimen. Artificial-intelligence-driven registration and reconstruction pipelines will spatially align these datasets with histological ground truth, enabling voxel-level correlation between antibody binding, ECM stiffness, and vascular architecture. This integrated framework directly links molecular drug engagement to the physical and vascular state of the TME at clinically relevant mesoscale resolutions. Aim 1 will develop and validate the integrated mFLIO² platform. We will implement structured-light mesoscopic FLI-FRET for quantitative whole-tumor mapping of antibody–receptor interactions, incorporate OCT and OCE modules for concurrent assessment of vascular and mechanical features, and deploy AI-based multimodal registration to align optical data with histopathology. Aim 2 will apply mFLIO² to HER2. xenograft and patient-derived xenografts tumor models to elucidate how TME stiffness and ECM composition or vascular organization modulate TZM–HER2 binding, drug response and treatment therapy. Pharmacologic agents that remodel ECM composition, including lysy Project Number: 1R01CA308771-01A1 | Fiscal Year: 2026 | NIH Institute/Center: National Cancer Institute (NCI) | Principal Investigator: Margarida Barroso (+1 co-PI) | Institution: ALBANY MEDICAL COLLEGE, ALBANY, NY | Award Amount: $648,579 | Activity Code: R01 | Study Section: Imaging Guided Interventions and Surgery Study Section[IGIS] View on NIH RePORTER: https://reporter.nih.gov/project-details/11450033