Background/Aim: The aim of this study was to examine whether the Wnt/β-catenin signal activation is a cause of radioresistance in colon cancer by assessing the β-catenin localization and its correlation with cancer stem cells (CSCs). Materials and Methods: The nuclear levels of β-catenin, the hallmark of Wnt activation, were analyzed in HCT116 and SW480 cells by immunohistochemistry, before and after irradiation. Further, we assessed CSC populations by staining for aldehyde dehydrogenase-1 (ALDH1) and CD44. Results: β-catenin was localized predominantly in the nucleus and plasma membrane in SW480 and HCT116 cells, respectively. Compared to HCT116 cells, SW480 cells displayed higher Wnt activation. At 24 h after irradiation, most of the DSBs in SW480 cells were repaired, but were still present in HCT116 cells. Additionally, compared to HCT116 cells, a significantly higher proportion of SW480 cells were ALDH1-and CD44-positive. Conclusion: Colon cancers with nuclear β-catenin accumulation demonstrated greater radio-resistance with a higher number of CSCs.There are two Wnt/β-catenin signaling pathways: the canonical pathway and the non-canonical pathway (1, 2). β-catenin is the key molecule in the canonical Wnt pathway. In Wnt-off state, βcatenin in the cytoplasm is within a protein complex composed of adenomatous polyposis coli (APC), Axin, glycogen synthase kinase 3β (GSK3β), and casein kinase 1α (CK1α), and phosphorylated by GSK3β and CK1α. Then, β-catenin is ubiquitinated and targeted for destruction by the proteasome. As a result, the amount of β-catenin is low. Conversely, in the Wnton state, Wnt ligands bind to the receptor complex composed of a Frizzled (Fz) receptor and low-density lipoprotein receptorrelated proteins (LRP5/6). This receptor recruits Disheveled (Dvl) to the plasma membrane. Dvl forms a complex with Axin, Fz, and LRP5/6 and acts as a direct competitive inhibitor of GSK3β. Thus, β-catenin escapes phosphorylation and accumulates in the cytoplasm. The stabilized β-catenin translocates into the nucleus, where it serves as a transcriptional co-activator and influences gene transcription. Thus, β-catenin localization to the nucleus reflects Wnt activity (3-5).The canonical Wnt/β-catenin signaling pathway plays an important role in cell proliferation, growth, and differentiation (6, 7). Mutations in Wnt signaling pathway components cause many diseases, including cancer. Furthermore, dysregulation of the Wnt signaling pathway is associated with the expansion of stem cell and progenitor cell lineages and is also highly associated with carcinogenesis (8-10). Most colorectal cancer (CRC) cases are caused by mutations in Wnt signaling pathway components (11-13). Originally, a mutation in the APC gene was associated with familial adenomatous polyposis (FAP). Approximately 1% of FAP cases progress to CRC (14,15). Furthermore, 85% of sporadic intestinal neoplasia cases have mutations in APC, whereas activating 6575

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Reactive oxygen species (ROS) play an important role in cell metabolism, but they can cause oxidative damage to biomolecules. Among ROS, the hydroxyl radical (·OH) is one of the most reactive molecules in biological systems because of its high reaction rate constant. Therefore, imaging of ·OH could be useful for evaluation of the redox mechanism and diagnosis of oxidative diseases. In vivo dynamic nuclear polarization-magnetic resonance imaging (DNP-MRI) is a noninvasive imaging method to obtain spatiotemporal information about free radicals with MRI anatomical resolution. In this study, we investigated the visualization of hydroxyl radicals generated from the Fenton reaction by combining DNP-MRI with a spin-trapping agent (DMPO: 5,5-dimethyl-1-pyrroline N-oxide) for ·OH. Additionally, we demonstrated the radical-scavenging effect using four thiol-related reagents by DNP-MRI. We demonstrated that DNP enhancement could be induced by the DMPO-OH radical using the DNP-MRI/spin-trapping method and visualized ·OH generation for the first time. Maximum DNP enhancement was observed at an electron paramagnetic resonance irradiation frequency of 474.5 MHz. Furthermore, the radical-scavenging effect was simultaneously evaluated by the decrease in the DNP image value of DMPO-OH. An advantage of our methods is that they simultaneously investigate compound activity and the radical-scavenging effect.

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