Senescent lung cells secrete COPD-associated SASPs, such as IL-6, IL-8, monocyte chemoattractant protein-1 (MCP-1), and plasminogen activation inhibitor-1 (PAI-1), which further promote chronic inflammation in COPD (Freund et al., 2010). This evidence concerns the gene CCL2 and chronic obstructive pulmonary disease.