Fig 2: SDC2 facilitates the membrane translocation of PDK1 by interacting with its PH domain in GC cells. A & B. Association of PDK1 and FGF2 with SDC2 (LC/MS analysis, Co-IP assay). C. Interaction of SDC2 and PDK1 in GC cells (Co-IP assays). D & E. Interaction of SDC2 and the PH domain of PDK1 (Co-IP assays, using HEK293T cells; molecular docking performed by Discovery StudioTM). F. Colocalization of SDC2 and PDK1 in AGS and HGC-27 cells (Double immunofluorescent staining). G. Effect of SDC2 on membrane translocation of PDK1 (Western blotting of lipid raft). H, I, & J. Dependence of the oncogenic function of SDC2 on the PDK1-AKT signaling pathway in GC cells (CCK8 assay, Transwell assay, and Western blotting. Scale bar: =100 µm). K. A schematic diagram showing the proposed mechanism.

Fig 3: SDC2 promotes proliferation and invasiveness of GC cells and its upregulation correlates with the activation of AKT pathway. A. Protein levels of SDC2 in five lines of GC cells and one line of normal gastric epithelial cells (GES-1) (Western blotting). B. Protein levels of SDC2 in three lines of GC cells after stable transfection with plasmids that promoted overexpression (OE-SDC2) or knockdown (shRNA) of SDC2 (Western blotting). C & D. Migration, invasion, and proliferation of three lines of GC cells that were transfected with different plasmids (Transwell assay, CCK8 assay. Scale bar: =100 µm). E & F. SDC2-associated signaling pathways in GC based on pathways and gene sets (KEGG Enrichment and Hallmark Analysis). G. Protein level of mesenchymal markers (N-cadherin, Vimentin) and p-AKT, in three lines of GC cells that were transfected with different SDC2 plasmids (Western blotting).

Fig 4: Upregulation of SDC2 correlates with poor prognosis in patients with GC. A. Overall survival and recurrence free survival in patients with low levels (N = 25) and high levels (N = 25) of SDC2 mRNA in GC tissues (SYSUCC cohort). B. SDC2 mRNA levels in specimens from two populations of patients with different T stages of GC (TCGA). C. Biological process (top), cellular components (middle), and molecular functions (bottom) related to SDC2 in GC (GO analysis). D. Expression of SDC2 in tumor tissues (T) and matched adjacent normal tissues (N) of four patients with GC (Western blotting). E. Representative images of SDC2 staining in GC tissue and adjacent normal tissue (Immunohistochemistry, scale bar: =100 µm). F. SDC2 expression, overall survival, and recurrence-free survival in GC patients with high expression (N = 54) and low expression (N = 54) of SDC2 in tumor tissues (Immunohistochemistry, FUSCC cohort).

Fig 5: SDC2 promotes GC tumor growth in vivo. A & B. Morphology, weight, and average volume of subcutaneous tumors formed by two lines of GC cells that were transfected with different plasmids (Xenograft transplantation, N=6). C. Staining for SDC2, pAKT, and Ki67 in tumors from the two xenograft models that were transfected with different plasmids (Immunohistochemistry, scale bar: 50 µm). D. Protein levels of N-cadherin, vimentin, pAKT, AKT, and SDC2 in tumors from the two xenograft models that were transfected with different plasmids (Western blotting).