Although the cytotoxic ability of PAR1CAR-T cells at the low ET ratio of 0.5 was relatively attenuated by adding CD4+CD25+ Treg cells, either original or newly converted ones, significant cytotoxic activities of PAR1CAR-T cells toward co-cultured tumor/CAF cells with or without additional Treg cells were observed, compared to the control, non-transduced CD3 T cells, and mock-transduced CD3 T cells (* p < 0.05 and ** p < 0.01; Fig. 7C, left panel). Here, CD4 is linked to neoplasm.