LNP-miR-155 cy5 Inhibitor Regulates the Copper Transporter via the β-Catenin/TCF4/SLC31A1 Signal for Colorectal Cancer Therapy

Lipid nanoparticle (LNP) delivery systems are widely used in the delivery of small-molecule drugs and nucleic acids. In this study, we prepared LNP-miR-155 by lipid nanomaterial technology and investigated the effects of LNP-miR-155 on β-catenin/transcription factor 4 (TCF4)/solute carrier family 31 member 1/copper transporter 1 (SLC31A1/CTR1) signaling and copper transport in colorectal cancer. For this, we used an LNP-miR-155 cy5 inhibitor and LNP-miR-155 cy5 mimics for the transfection of HT-29/SW480 cells. The transfection efficiency and uptake efficiency were detected by immunofluorescence. Relevant cell assays confirmed that the LNP-miR-155 cy5 inhibitor mediates the regulation of copper transport through the β-catenin/TCF4/SLC31A1 axis. The LNP-miR-155 cy5 inhibitor reduced cell proliferation, migration, and colony formation and promoted cell apoptosis. We also confirmed that miR-155 downregulates HMG box-containing protein 1 (HBP1) and adenomatous polyposis coli (APC) in cells and activates the function of β-catenin/TCF4 signaling. In addition, we found that the copper transporter, SLC31A1, is highly expressed in colorectal cancer cells. Furthermore, we also found that the complex β-catenin/TCF4 promotes the transcription of SLC31A1 by binding to its promoter region, which sustains the transport of copper from the extracellular region to the intracellular region and increases the activities of Cu²⁺-ATPase and superoxide dismutase (SOD). In summary, the LNP-miR-155 cy5 inhibitor regulates β-catenin/TCF4 by downregulating SLC31A1-mediated copper transport and intracellular copper homeostasis.