First Fluorescent Probe for TREX1 Enables Real-Time Tracking of DNA Repair and Immune Regulation in Cancer Cells.

Three Prime Repair Exonuclease 1 (TREX1) is the most abundant 3' exonuclease in human cells, playing a pivotal and complex role in both autoimmune regulation and cancer immunity. Despite its importance, existing methods have been insufficient for directly tracking the real-time dynamics of endogenous TREX1 in living cells. To address this gap, we developed a dual-modified DNA fluorescent probe (Probe-TREX1) that enables rapid quantification of TREX1 activity, live-cell imaging across subcellular compartments, and visualization of its distribution in tumor and adjacent nontumor tissues. Our results reveal that TREX1 levels in the nuclei of normal and cancer cells are comparable to or even higher than those in the cytoplasm. Upon stimulation with anticancer drugs, nuclear TREX1 levels, especially in euchromatin regions, rose rapidly, matching or exceeding the increases seen in the cytoplasm, suggesting a significant role for TREX1 in the nucleus. Notably, TREX1 expression was lower in hepatoblastoma and the other two investigated tumor tissues compared to adjacent non-tumor tissues, highlighting the complexity of TREX1's roles in DNA repair and immune response across different tumor types. This study introduces a valuable molecular tool for advancing our understanding of the diverse functions of TREX1, with a broad potential for evaluating and improving cancer therapies.