The results suggest that thisaerosolized let‐7b mimic is a promising approach for lung cancer prevention, and that the in vivo tumor inhibitory effects of let‐7b are mediated, at least in part, by immune‐promoting effects via downregulating PD‐L1 in tumors and/or PD‐1 on CD8+ T cells. The gene discussed is PDCD1; the disease is lung cancer.