TGFB1 and neoplasm: To further improve the cytotoxicity of PAR1CAR-T cells against tumor cells with lower PAR1 expression, we first treated six PDAC cell lines, namely CFPAC-1, Capan-1, ASPC-1, SU.8686, HPAF-II, and MIA PaCa-2, with 1 ng/mL TGF-β and examined their cell surface PAR1 levels by flow cytometry at indicated time points within 48 h (Additional file 2: Figure S2).