CD274 and cancer: Some studies have shown that PD-L1 inhibitors are a common immunotherapeutic agent targeting cancer cells [189,190,191,192,193,194,195,196,197,198], and the multifunctional liposomal nanocarriers siPD-L1@PM/DOX/LPs have excellent stability in serum and can effectively deliver siRNA into MCF-7 cells to reduce PD-L1 expression and enhance immunotherapeutic effects (Figure 5) [199].