A study that investigated the regulatory mechanism of circ-CPA4, let-7 miRNA, and programmed cell death ligand 1 (PD-L1) in lung cancer reports that circ-CPA4 regulates cell growth, stemness, mobility, and drug resistance in non-small-cell lung carcinoma (NSCLC) cells and inactivates CD8 + T cells in the tumor microenvironment via the let-7 miRNA/PD-L1 axis. The gene discussed is CD8A; the disease is neoplasm.