Poster CC13 - Non-invasive Tracking of Infiltration and Therapeutic efficacy of Nanoparticle-labeled CAR T-Cells in Glioblastoma Using MRI

Introduction: Chimeric antigen receptor (CAR) T-cell therapy has emerged as a groundbreaking treatment modality for blood cancers, yielding remarkable clinical outcomes. However, its application in solid tumors presents distinct challenges, necessitating precise monitoring techniques to elucidate therapeutic mechanisms and optimize efficacy. In this context, in vivo cell tracking becomes useful to delineate the dynamics of CAR T-cell infiltration, persistence, and therapeutic response within the complex microenvironment of solid tumors. In vivo tracking of CAR T-cells is crucial for understanding their infiltration, longevity, and therapeutic impacts within tumor environments. Utilizing magnetic resonance imaging (MRI), we leverage high-resolution imaging capabilities to monitor cellular processes, enhanced by the use of cellular imaging probes. This method provides a wealth of biological data concerning tumor characteristics and behavior.

Materials and

Methods: In our approach, we utilized nanoparticles known as ultra-small superparamagnetic iron oxide (USPIO) particles to tag CAR T-cells. This labeling allows for the non-invasive observation of the cells' movement and persistence in glioblastoma (GBM). The CAR T-cells employed were specifically designed to target the human epidermal growth factor receptor variant III and the IL13 receptor subunit alpha 2. Ultra-small iron oxide nanoparticles (NPs) are capable of non-invasive visualization through magnetic resonance imaging (MRI), along with MRI sequences like T2* mapping. In this study, we establish a methodology for effective ex vivo labeling of CAR T cells using iron oxide NPs. We evaluate the labeling efficiency and functionality of T cells through flow cytometry and transmission electron microscopy (TEM).

Results, Conclusions, and Discussions: Our findings indicate that USPIO labeling does not adversely affect the CAR T-cells' functional properties or cytotoxic capabilities.Nanoparticles (NPs) are successfully integrated into T cells within subcellular cytoplasmic vesicles, achieving high labeling efficiency without compromising the viability, proliferation, or effector function of the T cells. This includes maintaining their capability for cytokine production and antigen-specific cytotoxicity, as evaluated through in vitro assays. Additionally, we have shown that these labeled T cells can be tracked over time within tumors using MRI in a murine glioma model, demonstrating high sensitivity in detection. Our findings indicate that a uniform and widespread distribution of T cells in the tumor microenvironment (TME), as determined by T2* imaging, correlates with a positive tumor response to CAR T cell therapy . Conversely, areas within the tumor lacking sufficient T cell presence are associated with resistance to treatment.

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