Liu et al. [21] found that the tumorigenicity of pcSK9-KO tumor cells was reduced in mice, and programmed death receptor 1 (PD-1) mAb was injected to inhibit tumor growth in conjunction with PCSK9 inhibitors, suggesting that inhibition of tumor-derived PCSK9 can overcome drug resistance to PD-1 therapy. Here, PCSK9 is linked to neoplasm.