Similarly, in the immunotherapy of NSCLC, circ-CPA4 participated in the regulation of CD8+T cell response (Hong et al., 2020), while the overexpression of circFGFR1 led to drug resistance to programmed cell death protein-1 (PD-1) (Zhang et al., 2019). Here, PDCD1 is linked to non-small cell lung carcinoma.