Assessment of Metastatic Dissemination in Mouse Breast Carcinoma Models Using Magnetic Resonance Imaging (MRI)

Metastatic dissemination remains the principal cause of cancer-related mortality, yet methodologies capable of directly assessing the dissemination process in vivo remain limited. Tumor Microenvironment of Metastasis (TMEM) doorways are specialized intravasation sites that facilitate cancer cell entry into the circulation and represent validated predictors of metastatic recurrence in breast cancer. We previously developed the TMEM Doorway Activity-MRI (TDAM) assay, a magnetic resonance imaging-based approach that detects TMEM doorway-associated vascular opening (TAVO) events and provides a noninvasive estimate of cancer cell dissemination risk. Here, we describe detailed protocols for implementing the TDAM assay in preclinical mouse models of breast cancer, including spontaneous transgenic tumors, syngeneic transplant models, and patient-derived xenografts. The methodology covers tumor transplantation procedures, MRI acquisition, contrast-enhanced dynamic imaging, first-pass permeability mapping, and computational TDAM calculation. This protocol provides investigators with a standardized framework for evaluating metastatic dissemination, monitoring therapeutic interventions, and advancing the development of imaging biomarkers capable of informing metastatic risk and treatment response.