Cytoplasmic LIM domain only 2 enhances tumor endothelial cell migration through integrin β1-mediated focal adhesion signaling

The LIM domain only 2 (LMO2) is a nuclear transcriptional regulator that influences cell fate in hematopoiesis and vasculogenesis. Recent evidence indicates that LMO2 also functions as a signaling molecule in the cytoplasm of cancer cells. However, its role in tumor endothelial cells (ECs) and angiogenesis remains unclear. In this study, we explored the cytoplasmic role of LMO2 in tumor angiogenesis using a three-dimensional microfluidic sprouting model. LMO2 was found to be enriched in the cytoplasm of migrating ECs, along with increased expression of vascular endothelial growth factor (VEGF) receptor 2. VEGF stimulation elevated cytoplasmic LMO2 levels, and LMO2 was enriched at tumor margins in vivo. Proteomic screening identified integrin β1 (ITGB1) as a potential interactor with LMO2, and their interaction was confirmed through co-immunoprecipitation and proximity ligation assays. Overexpressing LMO2 enhanced focal adhesion signaling, as indicated by increased activation of FAK, Src, and ERK, and promoted EC migration without altering total ITGB1 levels. Knocking down ITGB1 reversed these effects, suggesting that the LMO2–ITGB1 interaction is essential for focal adhesion signaling and EC migration. Importantly, these effects depended on cytoplasmic, not nuclear, LMO2. Our findings reveal a previously unknown cytoplasmic role of LMO2 in regulating focal adhesion dynamics and endothelial behavior. Targeting the LMO2-ITGB1 pathway could be a promising strategy for anti-angiogenic therapy.