Among diverse cancers, lung cancer ranks the first in morbidity and mortality, posing a growing threat to human health.1 Small-cell lung cancer (SCLC), which accounts for approximately 10%–15% of cases, is a cancer phenotype with high recurrence rate and growth fraction, resulting in poor outcomes.2 3 The programmed cell death protein 1 (PD-1) and programmed death-ligand 1 (PD-L1) inhibitors have been confirmed effective in treating non-small-cell lung cancer (NSCLC). Here, PDCD1 is linked to lung cancer.