Figure 1. Epithelial-mesenchymal transition increases tumor cell adherence to collagen through α₁β₁ integrin.

(A) Cell adherence was quantified 1 hour after the indicated KP cells were seeded on wells coated with collagen 1 (Col1), collagen IV (Col4), fibronectin, BSA, or nothing, and OD₅₉₅ values are shown in the heatmap. E, epithelial; M, mesenchymal. n = 4. (B) Cell spreading assay on Col1. Cells were plated in Col1-coated plates for 1 hour, and percentages of spread cells were quantified. Scale bar: 50 μm. (C) Quantitative reverse transcription PCR analysis of the mRNA levels of ZEB1 and Col1 receptors in KP cell lines (Pearson correlation). (D) Western blot analysis of Itga1 and Itgb1 in KP cell lines classified as epithelial or mesenchymal. β-Actin was used as a loading control. (E) Heatmap illustration of gene expression levels in lung adenocarcinoma and squamous cell carcinoma data sets (n = 1016 tumors) in The Cancer Genome Atlas. An epithelial-mesenchymal transition score was correlated with the levels of collagen receptors using the Pearson coefficient (r value). (F) Cell adherence was quantified 1 hour or 2 hours after the indicated cells were seeded on uncoated wells or on wells coated with Col1. n = 4. **P < 0.01. (G) Cell spreading assay on Col1. Percentages of spread cells were quantified. Scale bar: 100 μm. ***P < 0.001. (H) Quantitative reverse transcription PCR analysis of Col1 receptors. (I) Western blot analysis of Itga1 in 393P_Vec and 393P_ZEB1 cells. Data are shown as the mean ± SEM from a single experiment incorporating biological replicate samples (n = 3, unless otherwise indicated) and are representative of at least 2 independent experiments. *P < 0.01; ***P < 0.001. Two-tailed Student’s t test.