Harnessing ecDNA Detection in Antigen-Presenting Cells for Anti-Tumor Immunity

PROJECT SUMMARY Despite dozens of agents targeting the myeloid checkpoint CD47 entering clinical trials, their variable tumor- type impact has spurred a search for complementary biologics to augment tumor inflammation. Antitumor immune responses in antigen-presenting cells (APCs) are catalyzed by the engulfment of tumor cells and the recognition of tumor-derived DNA by cytoplasmic nucleic acid sensors. Nevertheless, these immunogenic processes are hindered by phagocytic checkpoints and inefficient translocation of nucleic acids from phagolysosomes into the cytosol. Cytoplasmic extrachromosomal DNA (ecDNA) functions as a potent innate immunostimulant. However, no therapeutic strategies specifically target phagolysosomal release of ecDNA or other tumor-derived contents within professional APCs. To overcome these challenges, we recently engineered an antibody-drug conjugate (ADC) that targets the “don’t eat me” signal CD47 linked to the bacterial toxin listeriolysin O from the intracellular bacterium Listeria monocytogenes via a cleavable linker (CD47-LLO). CD47-LLO promotes the phagocytosis of cancer cells followed by the activation of LLO which disrupts phagolysosomal membranes and allows for cytosolic escape of tumor-derived contents in APCs. The current proposal explores the use of CD47-LLO to promote antitumor immune responses against recalcitrant tumor types that produce high levels of ecDNA. Aim 1 of the proposal will mechanistically examine how ecDNA detection in APCs triggers potent and broad antitumor signaling pathways. For Aim 2, we will examine how phagolysosomal release of ecDNA stimulates both innate and adaptive immune responses. Finally, for Aim 3, we will evaluate the antitumor effect of CD47-LLO in combination with frontline therapies in animals bearing gliomas or colorectal cancers with high ecDNA expression. If successful, this proposal will support bench-to- bedside translation of an immunostimulatory ADC with potential to destroy diverse cancers that harness ecDNA for survival. This research will be performed by Dr. Benjamin Schrank, a radiation oncologist at the University of Texas MD Anderson Cancer Center. Dr. Schrank will be advised by a multidisciplinary mentoring team consisting of physician-scientists, oncologists, immunologists, and tumor biologists. His primary mentor, Dr. Wen Jiang, is a recognized expert in cancer nanomedicine; his co-mentor, Dr. Betty Kim is known for her neurosurgical and preclinical work on glioblastoma. They will be joined by Dr. Linghua Wang, a pioneer in tumor immunology and spatial transcriptomics; Dr. Jian Hu, a leader in cancer neuroscience; and Dr. Michael Curran, an internationally recognized cancer immunotherapy expert. MD Anderson provides an outstanding environment for Dr. Schrank’s career development. Resources and equipment critical to the proposed research are readily available on campus. Together, the proposed research, training, and career development plan will provide Dr. Schrank with the expertise needed to achieve independence and apply for his first R01.