Activity-Based Bioluminescent Logic-Gate Probe Reveals Crosstalk Between the Inflammatory Tumor Microenvironment and ALDH1A1 in Cancer Cells

Cancer cells with high expression of aldehyde dehydrogenase 1A1 (ALDH1A1) are more resistant to chemotherapy, contribute to tumor progression, and are associated with poor clinical outcomes. ALDH1A1 plays a critical role in protecting cells from reactive aldehydes and, in the case of stem cells, regulates their differentiation through the retinoic acid signaling pathway. Despite the importance of this enzyme, methods to study ALDH1A1 high-expressing cancer cells in vivo remain limited. In this work, we developed AlDeLuc, the first logic-gated bioluminescence probe designed to selectively evaluate ALDH1A1 activity in tumor cells. The probe is sequentially activated by acidic intracellular compartments (i.e., endosomes) and ALDH1A1, ensuring precise detection of ALDH1A1 high-expressing cells and minimizing off-target detection of non-ALDH1A1 cells. Beyond demonstrating efficacy in multiple cancer cell lines and a murine model of breast cancer, we employed AlDeLuc to investigate how the population of ALDH1A1 high-expressing cells is influenced by the inflammatory status of a tumor in the context of a high-fat diet. These findings establish a molecular link between obesity, inflammation, and tumor progression.