Figure 4. Adhesion and spreading of mammary carcinoma cells.

(A) Cartoon depiction of murine SDC1-mediated cell spreading of MDA-MB-231 mammary carcinoma cells occurring through both protein- and GAG-mediated interactions with integrin α_vβ₃ and GAG-mediated interactions with vitronectin (VN), for which α_vβ₃ is the canonical receptor. Note: human and mouse SDC1 are highly homologous (78%) in the region responsible for α_vβ₃ integrin-mediated activation⁵³. (B) Quantification of cell spreading of wild-type MDA-MB-231 cells on vitronectin surfaces. (C) Representative fluorescence microscopy images of wild-type MDA-MB-231 cells plated in media supplemented with indicated SDC family proteins (2 μM) or heparin (0.4 μM). Adhesion and spreading of cells were inhibited by addition of soluble glycoconjugates and SDC3_80,82,89. Cells were fixed and stained for phalloidin (red) after 2 hr on VN matrix. Scale bar: 50 μm. Data representative of three biological replicates. (D) Quantification of cell spreading in wild-type (WT) and SDC1 knockdown (SDC1^KD) cells. Bar graphs represent means and error bars represent SEM. One-way ANOVA with Tukey’s post-hoc, (*) p <0.0332, (**) p <0.0021, (***) p <0.0002, (****) p <0.0001. Error bars represent SEM. For each condition, n >10 images across two biological replicates.