The link between APE1 amount in sera and tumor progression and chemoresistance was proved in a previous study performed on non-small-cell lung cancer (NSCLC) patients, in which the levels of serum APE1 (sAPE1) resulted significantly more elevated than in healthy controls and were associated with a worse progression-free survival (28). The gene discussed is APEX1; the disease is non-small cell lung carcinoma.