Ultrasound-Controlled Immunotherapy for Targeted Treatment of Solid Tumors

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Project Summary Advances in synthetic biology have enabled the development of increasing numbers of cell-based diagnostic and therapeutic tools. However, controlling these cells in vivo is difficult and current methods to communicate with engineered cells either suffer from poor spatiotemporal resolution or require invasive operations. In order to improve safety and efficacy of cell-based therapies, robust methods to control gene expression in vivo are required. Temperature is a unique communication signal as it can be modulated with millimeter precision deep within tissues non-invasively using focused ultrasound (FUS). In addition, cells have already evolved the ability to sense changes in temperature through heat shock promoters (HSPs). These genetic elements are ubiquitous across organisms, providing a platform to develop genetic circuits that will activate upon FUS heating. Combining the spatial control offered by FUS with cellular engineering to confer thermal sensitivity will allow us to create thermally responsive cells that will activate in specific locations following FUS treatment. One rapidly growing field that could benefit from spatially controlled gene expression is cell-based cancer immunotherapy. Immunotherapy has recently emerged as a promising new class of cancer therapies with transformative results in hematological malignancies. However, engineered cell-based immunotherapies such as CAR T-cells and immunomodulatory agents such as cytokines must overcome significant challenges before becoming more widely applicable for solid tumors. In recent clinical trials, CAR T-cells have attacked healthy tissues if their targeted antigen is not tumor limited, resulting in massive peripheral toxicity and death. Systemic cytokine therapy can also cause life-threatening adverse effects such as vascular leak syndrome. Both types of immunotherapy could benefit from spatially controlled therapeutic expression. This project’s overall goal is to develop HSP-driven circuits in primary T-cells that will allow thermal stimuli delivered by FUS to active therapeutic genes expression. Initial experiments will focus on developing T-cells in vitro that will respond to bulk heating by transiently releasing cytokine to boost CAR performance in an autocrine fashion or activating permanent CAR expression specifically in the tumor. We will accomplish this by developing HSP driven circuits that feature drug induced transactivators or Cre Recombinase. After validating these circuits in vitro, we will test their performance upon FUS treatment in vivo using a murine SKBR3 tumor model and an anti-HER2 CAR. This model will allow us to develop and demonstrate the performance of robust, FUS-activated primary T-cells with two distinct payload outputs. This proposed approach represents a novel combination of cellular engineering and therapeutic ultrasound to spatiotemporally control cell-based immunotherapies with direct application to solid tumor treatment. This technology also has substantial potential for further development and adaption to other cell types which may facilitate both basic science and translational research.