For lung adenocarcinoma, four genes (H2AFX, LIG3, NEIL1, and PCNA) in the “non-smoker vs. smoker” and “non-smoker vs. ex-smoker (≤15 years)” categories show the same gene expression patterns as the PM versus the CR0 cells: up-regulated H2AFX, LIG3, and PCNA and down-regulated NEIL1. However, the expressions of these four genes are all becoming opposite in “smoker vs. ex-smoker (≤15 years)”, “smoker vs. ex-smoker (>15 years)”, and “ex-smoker (≤15 years) vs. ex-smoker (>15 years)”. This evidence concerns the gene PCNA and lung adenocarcinoma.