CD51 promotes gastric cancer stemness via blocking Numb-mediated Notch1 degradation.

Gastric cancer (GC) remains a lethal malignancy with poor prognosis largely due to cancer stem cell (CSC)-driven metastasis, recurrence, and chemoresistance. This study identifies CD51 (integrin αv) as a pivotal regulator of GC stemness and malignant progression. Bioinformatics analysis of TCGA data revealed significant CD51 upregulation in GC tissues, correlating with advanced tumor stage and poor survival. Functional assays demonstrated that CD51 enhances CSC properties, including tumorsphere formation, migration, invasion, and oxaliplatin resistance. Mechanistically, CD51 interacts with Numb, a negative regulator of Notch signaling, to divert Notch1 receptor trafficking from lysosomal degradation to plasma membrane recycling, thereby amplifying Notch pathway activation. Single-cell RNA sequencing and clinical validations confirmed CD51's superior correlation with stemness scores compared to canonical CSC markers. Pharmacological inhibition of CD51 using cilengitide suppressed CSC phenotypes in vitro and inhibited tumor growth in patient-derived organoids and xenograft models. These findings establish CD51 as a novel CSC biomarker and therapeutic target, offering a strategy to disrupt Notch-dependent stemness and chemoresistance in GC.