In a xenograft model of MCF-7 cells that expressed modest levels of HER2, administration of either group of CAR-T cells led to moderately but comparably retarded tumor growth, suggesting the non-inferiority of H28E compared with conventional CAR-T cells in combating malignancies expressing low-density tumor antigens (Supplementary Fig. 15d–f). This evidence concerns the gene ERBB2 and neoplasm.