Fig. 1

Immunohistochemistry for PGAM 5 expression in background lung (a-d), squamous cell carcinoma (e-h) and alveolar macrophages at the edge of cancer (i-l). Magnification ×40. The first row shows background lung tissue with alveolar walls and macrophages in the alveolar space. PGAM 5 is expressed by alveolar macrophages (only cell type showing brown staining in this row), with higher expression in healthy smokers and COPD groups, compared to non-smokers. The second row shows cancerous tissue with epithelial cells and stromal cells. PGAM 5 is expressed by the malignant epithelial cells (showing brown staining), but not stroma, in all three groups of patients. There was no difference in PGAM5 expression by the epithelial cells across the 3 groups of patients. The third row shows alveolar spaces at the edge of cancerous tissue. PGAM5 is expressed in the alveolar macrophages (only cell type showing brown staining in this row)