Previous studies have found that collagen increases anti-programmed cell death protein 1 (PD-1)/PD-L1 resistance by depleting CD8+ T cells, which is associated with tumor immunosuppression and drug resistance (Chakravarthy et al., 2018; Mariathasan et al., 2018; Peng et al., 2020). Here, PDCD1 is linked to neoplasm.