For example, based on complete exome sequencing of tumor cells from 42 non-small cell lung cancer (NSCLC) patients who developed acquired drug resistance after single PD-1 or PD-1 combined with CTLA-4 blocking therapy, it was found that the occurrence of acquired drug resistance was related to the loss of neoantigens, not only by eliminating tumor subclones, but also by chromosomal loss of the trunk (Anagnostou et al., 2017). The gene discussed is PDCD1; the disease is non-small cell lung carcinoma.