Overexpression of integrin α5 subunit and knock down of α6 subunit decreased pulmonary metastasis of 4T1 cells. 1 × 106 4T1 control, GFP-4T1, 4T1-α5, and 4T1-α6-shRNA1 cells were resuspended in 0.1 ml PBS and used to inject nude mice in their lateral tail veins. After four weeks, the mice were euthanized and their lungs were removed, fixed in 4% paraformaldehyde, and analyzed for metastasis. Representative examples of the lung tissues from each group are shown. A: Lungs from 4T1 control-cell-injected mice; B: Lungs from 4T1-GFP cells injected mice., C: Lungs from 4T1-α5 injected mice., D: Lungs from mice injected with 4T1 α6-shRNA1; Ai, Bi, Ci, and Di: Lung images taken right after formaldehyde fixation. Aii, Bii, Cii, and Dii : Lungs stained with India ink:. Aiii, Biii, Ciii, Diii: H&E stained lung sections. Aiv, Biv, Civ, and Div: Ki67 stained lung sections. Scale bar: 100 microns.