Imaging Tumor-Targeting Bacteria Using ¹⁸F-Fluorodeoxysorbitol Positron Emission Tomography

Background: Microbial-based cancer treatments are an emerging field, with multiple bacterial species evaluated in animal models and some advancing to clinical trials. Noninvasive bacteria-specific imaging approaches can potentially support the development and clinical translation of bacteria-based cancer treatments by assessing the tumor and off-target bacterial colonization. Methods: 18F-Fluorodeoxysorbitol (18F-FDS) positron emission tomography (PET), a bacteria-specific imaging approach, was used to visualize an attenuated strain of Yersinia enterocolitica, currently in clinical trials as a microbial-based cancer treatment, in murine models of breast cancer. Results: Y. enterocolitica demonstrated excellent 18F-FDS uptake in in vitro assays. Whole-body 18F-FDS PET demonstrated a significantly higher PET signal in tumors with Y. enterocolitica colonization compared to those not colonized, in murine models utilizing direct intratumor or intravenous administration of bacteria, which were confirmed using ex vivo gamma counting. Conversely, 18F-fluorodeoxyglucose (18F-FDG) PET signal was not different in Y. enterocolitica colonized versus uncolonized tumors. Conclusions: Given that PET is widely used for the management of cancer patients, 18F-FDS PET could be utilized as a complementary approach supporting the development and clinical translation of Y. enterocolitica-based tumor-targeting bacterial therapeutics.