ST3GAL6 expression MM cell lines. (A) ST3GAL6 expression MM cell lines; qRT-PCR for ST3GAL6 gene expression in MM cell lines MM1S, MM1R, U266, RPMI-8226 (RPMI), and H929 compared with CD138 cells isolated from normal healthy donor bone marrow (NBM) P < .0001. (B) Western blot analysis demonstrating the expression level of ST3GAL6 protein in CD138⁺ cells isolated from the bone marrow of healthy controls (NBM) compared with MM cell lines MM1S, MM1R, U266, RPMI8226, and H929. (C) Flow cytometry demonstrating surface expression of MAA lectin, which binds to α-2,3 sialylated glycans, at the surface of MM cell lines MM1S, MM1R, U266, RPMI8226, and H929 compared with CD138⁺ cells isolated from healthy donor bone marrow (NBM). MAA is synthesized by ST3GAL6, and the presence of this lectin at the cell surface is indicative of ST3GAL6 activity in these cells.