Structural basis of laminin mimicry by E. coli CNF1 and its therapeutic potential for cancer immunotherapy.

The E. coli CNF1 toxin hijacks the host laminin 511 receptor, Lu/BCAM, to enter cells. Here, we present the high-resolution cryo-EM structures of full-length CNF1, the CNF1-BCAM complex, and the physiological laminin 511-BCAM complex. Structural analysis uncovers that CNF1 targets the V2 domain of BCAM, mimicking the interaction mode of laminin 511. We demonstrate that CNF1 binds BCAM with higher affinity than laminin 511, effectively displacing the physiological ligand from the cell surface. Leveraging this high-affinity interaction, we engineered a CNF1 D5-based T-cell engager (TCE). This TCE potently directs T cells to kill BCAM-overexpressing tumor cells in vitro and suppresses tumor progression in a metastatic ovarian cancer mouse model in female mice. These findings provide structural insight into how CNF1 hijacks the BCAM receptor and show how a pathogen-derived, high-affinity interaction can be harnessed to redirect T cells against BCAM-expressing tumors.