MSLN and breast cancer: One concern is that the strategy may hinder the broad application of CAR-T cells because of tumor antigen heterogeneity, e.g., MSLN was found in 25 ~ 30% of breast cancers, 40 ~ 45% of colon cancers and 80 ~ 85% of pancreatic cancers [15], thus choosing a broadly expressed antigen on tumor cells to design CCR may promote the clinical application of CAR-T cells using combinatorial antigen recognition strategy.