Figure 1.

Endoplasmic reticulum (ER) stress is differentially regulated by extracellular matrix (ECM) stiffness. (A) Principal component analysis (PCA) of the RNA-sequencing (RNA-seq) datasets obtained from MDA-MB-231 cells cultured on soft and stiff matrices. (B) Volcano plot of differentially expressed genes (DEGs) in MDA-MB-231 cells according to ECM stiffness based on RNA-seq results. Genes with significantly decreased expression are shown in green; genes with significantly increased expression are shown in red. (C) Heatmap of all DEGs between cells cultured on soft matrix and stiff matrix. (D) Gene set enrichment analysis (GSEA) of ECM stiffness-dependent signaling pathways. (E) Expression of ER stress and Golgi stress markers in MDA-MB-231 cells cultured on 0.5 kPa polyacrylamide gels (PAGs) or culture dishes was quantified by RT-qPCR. Values represent the mean ± SD of three independent experiments and were analyzed using Student’s t-test. ** p < 0.01, N.S. not significant. (F) MDA-MB-231 cells were cultured on 0.5 kPa PAGs or dishes for 48 h. Cell lysates were used for Western blotting analysis of the ER stress markers Ero1-Lα, Calnexin (CANX), IRE1α, and BiP. (G) MDA-MB-231 cells were cultured on non-adherent or adherent plates for 48 h. Cell lysates were used for Western blotting analysis of the ER stress markers Ero1-Lα, Calnexin, IRE1α, and BiP. GAPDH was analyzed as a loading control in all Western blot assays.