CD274 and breast cancer: In a PD-L1/ErbB2 double-positive breast cancer xenograft model, dual CAR-NK cells consistently outperformed single-target controls.<h4>Conclusions</h4>Dual targeting of PD-L1 and ErbB2 enhances CAR-NK cell efficacy against refractory solid tumors by providing resilience to antigen heterogeneity and amplifying antitumor signaling through cooperative activation.