CLDN6 and neoplasm: Using a CAR targeting claudin 6 (CLDN6), a tight junction protein, as a model, Sahin and colleagues demonstrate that intravenous administration of CLDN6 RNA-LPX can efficiently transfect APCs in the spleen and amplify adoptively transferred CLDN6 CAR T cells in both NSG mice and immunocompetent mice (Reinhard et al., 2020), resulting in marked control of CLDN6-expressing tumor progression.