CLDN4 and cancer: To investigate targeting of liposomes to cell surface-expressed CLDN4 in vitro, we assessed the cytotoxicity of D@C-LPs in three different cancer cell lines that differentially express CLDN4: ASPC-1 and KPC960 cells, which express CLDN4, and A549 cells, which are negative for CLDN4 expression (Fig. 3A).